Unprecedented and highly stable lithium storage capacity of (001) faceted nanosheet-constructed hierarchically porous TiO2/rGO hybrid architecture for high-performance Li-ion batteries     

Wen-Bei Yu  Zhi-Yi Hu  Jun Jin  Min Yi  Min Yan  Yu Li  Hong-En Wang  Huan-Xin Gao  Li-Qiang Mai  Tawfique Hasan  Bai-Xiang Xu  Dong-Liang Peng  Gustaaf Van Tendeloo  Bao-Lian Su 《国家科学评论(英文版)》2020,7(6):1046

Active crystal facets can generate special properties for various applications. Herein, we report a (001) faceted nanosheet-constructed hierarchically porous TiO₂/rGO hybrid architecture with unprecedented and highly stable lithium storage performance. Density functional theory calculations show that the (001) faceted TiO₂ nanosheets enable enhanced reaction kinetics by reinforcing their contact with the electrolyte and shortening the path length of Li⁺ diffusion and insertion-extraction. The reduced graphene oxide (rGO) nanosheets in this TiO₂/rGO hybrid largely improve charge transport, while the porous hierarchy at different length scales favors continuous electrolyte permeation and accommodates volume change. This hierarchically porous TiO₂/rGO hybrid anode material demonstrates an excellent reversible capacity of 250 mAh g^–1 at 1 C (1 C = 335 mA g^–1) at a voltage window of 1.0–3.0 V. Even after 1000 cycles at 5 C and 500 cycles at 10 C, the anode retains exceptional and stable capacities of 176 and 160 mAh g^–1, respectively. Moreover, the formed Li₂Ti₂O₄ nanodots facilitate reversed Li⁺ insertion-extraction during the cycling process. The above results indicate the best performance of TiO₂-based materials as anodes for lithium-ion batteries reported in the literature.  相似文献   

Enabling Mg metal anodes rechargeable in conventional electrolytes by fast ionic transport interphase     

Ruijing Lv  Xuze Guan  Jiahua Zhang  Yongyao Xia  Jiayan Luo 《国家科学评论(英文版)》2020,7(2):333

Rechargeable magnesium batteries have received extensive attention as the Mg anodes possess twice the volumetric capacity of their lithium counterparts and are dendrite-free. However, Mg anodes suffer from surface passivation film in most glyme-based conventional electrolytes, leading to irreversible plating/stripping behavior of Mg. Here we report a facile and safe method to obtain a modified Mg metal anode with a Sn-based artificial layer via ion-exchange and alloying reactions. In the artificial coating layer, Mg₂Sn alloy composites offer a channel for fast ion transport and insulating MgCl₂/SnCl₂ bestows the necessary potential gradient to prevent deposition on the surface. Significant improved ion conductivity of the solid electrolyte interfaces and decreased overpotential of Mg symmetric cells in Mg(TFSI)₂/DME electrolyte are obtained. The coated Mg anodes can sustain a stable plating/stripping process over 4000 cycles at a high current density of 6 mA cm⁻². This finding provides an avenue to facilitate fast ion diffusion kinetics of Mg metal anodes in conventional electrolytes.  相似文献   

Polyphosphonium-based ion bipolar junction transistors     

Erik O. Gabrielsson  Klas Tybrandt  Magnus Berggren 《Biomicrofluidics》2014,8(6)

Advancements in the field of electronics during the past few decades have inspired the use of transistors in a diversity of research fields, including biology and medicine. However, signals in living organisms are not only carried by electrons but also through fluxes of ions and biomolecules. Thus, in order to implement the transistor functionality to control biological signals, devices that can modulate currents of ions and biomolecules, i.e., ionic transistors and diodes, are needed. One successful approach for modulation of ionic currents is to use oppositely charged ion-selective membranes to form so called ion bipolar junction transistors (IBJTs). Unfortunately, overall IBJT device performance has been hindered due to the typical low mobility of ions, large geometries of the ion bipolar junction materials, and the possibility of electric field enhanced (EFE) water dissociation in the junction. Here, we introduce a novel polyphosphonium-based anion-selective material into npn-type IBJTs. The new material does not show EFE water dissociation and therefore allows for a reduction of junction length down to 2 μm, which significantly improves the switching performance of the ion transistor to 2 s. The presented improvement in speed as well the simplified design will be useful for future development of advanced iontronic circuits employing IBJTs, for example, addressable drug-delivery devices.There has been a recent interest in developing diodes^1–4 and transistors^4–8 that conduct and modulate ion currents. Such non-linear iontronic components are, for example, interesting as they allow further control of ions in, for instance, electrophoretic drug delivery devices. A range of microfabricated diodes,^9–11 transistors,^12,13 and circuits^9,14 has been constructed using ion-selective membranes. These membranes contain fixed charges of either polarity, compensated by mobile ions of opposite charge (counter-ions). When immersed in an electrolyte, counter-ions can move through the membrane, while ions with the same charge as the fixed charges (co-ions) are repelled. This renders the membrane selective for the counter-ion and can therefore be considered as p- or n-type ion conductors. By combining two membranes of opposite polarity, a bipolar membrane (BM) configuration is obtained¹⁵ (Figure 1(a)). The BM junction can be biased by an ion current in the reverse and forward directions, respectively.^16,17 This modulates the ion concentration inside the BM, and thus the ionic conductivity, which then results in an current rectification.^2,18 In the three-terminal ion bipolar junction transistor¹² (IBJT), an ion-selective base (B) is connected to oppositely selective emitter (E) and collector (C), forming two BM configurations (EB and BC) (Figure 1(b)). pnp- and npn-IBJTs have been constructed¹⁴ from photolithography patterned poly(styrene sulfonate) (PSS, p-selective) and quaternized poly(vinylbenzyl chloride) (n-selective) as emitter, collector, and base. In these devices, a neutral poly(ethylene glycol) (PEG) electrolyte is typically inserted into the junction to separate the base from the emitter and collector,¹² in order to avoid¹⁹ electric field enhanced (EFE) water dissociation¹⁶ (Figure 1(a)). EFE water dissociation is typically observed in BMs²⁰ and produces water ions inside the BM under reverse bias, which prevents proper IBJT operation. In PEG-IBJTs, the current between the emitter and collector (I_C) is thus modulated by controlling the ion concentration inside the PEG-junction.²¹ Ions are injected or extracted into the junction depending on the bias of the base (V_EB). In a npn-IBJT, a positive bias is typically applied between emitter and collector (V_EC), thus allowing anions to migrate from the emitter to the collector. In the cut-off mode (Figure 1(c)), a negative bias V_EB is applied, resulting in reverse bias of both EB and BC. Cations in the junction will migrate into the base, while anions will primarily migrate into the collector, due to the higher collector bias. This base current (I_B) will extract ions from the junction, which decreases the ionic conductivity in the junction resulting in a low I_C. Eventually, the resistive characteristics for ion charge transport, between the emitter and collector, will be entirely dominated by the junction. This gives that most of the applied V_EC is consumed across the junction with only a minimal voltage potential drop across the emitter and base terminals.Open in a separate windowFIG. 1.(a) The modes of operation for a BM; forward bias (high conduction and ion accumulation), reverse bias (low conduction and ion depletion), and EFE water dissociation (high conduction, formation of ions). (b) Illustrations of an npn-IBJT, with anion-selective emitter (E) and collector (C) forming a junction with a cation-selective base (B). (c) In cut-off mode, the base and collector extract ions from the junction, prohibiting co-ion migration through the base. (d) In active mode, the forward biased EB injects ions into the base, thus allowing anions from the emitter to migrate as co-ions through the base into the collector.In the active-mode of the npn-IBJT (Figure 1(d)), the V_EB bias at the base is reversed (i.e., now positive). This causes injection of cations, from the base, and anions, from the emitter, into the junction. As the ion concentration increases, anions from the emitter can start to drift across the junction to the collector, thus a high I_C is obtained. The high concentration of ions inside the junction is reflected in a low resistive value for ion transport. This now causes the voltage to drop over the emitter and collector terminals, thus lowering the EB forward bias and the injection of ions from the base. At the collector-junction interface, the extraction of anions produces an ion depletion zone and a corresponding voltage drop. Thus, in the active-mode, the applied V_EC is primarily consumed across the emitter and collector terminals and also at the collector-junction interface.The switching speed of an IBJT should be strongly correlated to the distance separating the emitter and collector,¹⁴ as this length determines the volume that needs to be filled or emptied with ions causing modulation of ions in the junction. To achieve a fast-switching IBJT, the junction volume, i.e., the collector-emitter separation, should be as small as possible. However, EFE water dissociation must be avoided since this process ruin the IBJT operation. EFE water dissociation is, in part, driven by the appearance of a large potential drop across a small distance, as occurring at the interface of a BM under reverse bias, producing a high electric field that accelerates the forward reaction rate of water auto-dissociation.¹⁶ Miniaturization of the collector-emitter distance is therefore problematic, as the separation inside the EB and BC BMs evidently also mush shrink, resulting in higher reverse bias electric fields across the BMs and thus promoting EFE water dissociation. The problem of EFE water dissociation in an IBJT primarily manifests itself in the cut-off mode, as water ions are generated in the reversed biased EB and BC BMs. These ions produce an elevated cut-off I_C, and hence deteriorate the IBJTs on–off performance. Here, we report an IBJT, in which the EFE water dissociation is avoided by the use of a novel polyphosphonium-based anion-selective material, which previously has been shown to prevent EFE water dissociation in BM diodes.¹¹ This allows the collector and emitter to directly contact the base without an intermediate PEG-layer. Without the need for a PEG-separator inside the BMs, the collector-emitter distance is reduced to only 2 μm.Polyphosphonium-based npn-IBJTs were produced following the same manufacturing protocol as was reported for polyphosphonium-based ion diodes.¹¹ Conjugated polymer electrodes and cation-selective base was patterned from ∼200 nm thick poly(3,4-ethylenedioxythiophene):polystyrene sulfonate film on polyethylene terephthalate-sheets using photolithography and dry-etching. The base was rendered electronically insulating by chemical overoxidation via exposure to sodium hypochlorite through a mask. A 2 μm thick SU8-layer was patterned on-top of this configuration, with an opening defining the actual junction. 1 μm thick polyphosphonium-based anion-selective emitter and collector were deposited and patterned using photolithography and dry-etching, to overlap with the base at the opening of the SU8. Finally, a second 10 μm thick layer of SU8 was used to seal the junction. The membranes were hydrated by incubation in dH2O for 24 h before any measurements were carried out. Aqueous 0.1M NaCl electrolytes were used during the measurement. All electrical measurements were performed using a Keithley 2602 source meter.The switching characteristics of the npn-IBJT were obtained by applying V_EC of 10 V and alternating V_EB at ±3 V for various duration of time, see Figure ​Figure2.2. A periodic 5 s switching with 8 Hz measurement rate was used to record the dynamics of the turn-on/off characteristics of the device. When V_EB switches from −3 to +3 V, there is a quick increase in the I_B, as ions from the base and emitter migrate into the emitter/base junction. After a delay of ∼0.25 s, I_C starts to increase due to the increased ion concentration in the emitter/base junction and the subsequent diffusion of anions into the base. As the I_C increases, the I_B decreases as the voltage drop between the emitter and base decreases, and after ∼2 s I_C reaches 90% of the steady state on-current level. For longer on-switching times, the I_B and I_C stay stable over 30 s, after which a small increase is observed. This current-drift in both I_B and I_C is likely due to the contribution of co-ion migration. As cations from the base migrate into the emitter as co-ions, the conductivity in the emitter increases, leading to an increased I_C value. This increases the ion concentration at the base, which gives less selective ion injection and thus more cation injection from the base, i.e., a higher I_B.Open in a separate windowFIG. 2.Emitter-collector current response as the IBJT is switched between cut-off (V_EB = −3 V) and active mode (V_EB = 3 V) for V_EC = 10 V, at 5 s and 120 s periods.As V_EB is switched back to −3 V, there is a sharp negative peak in I_E as ions are extracted from the junction, which occur mainly through the base (cations) and collector (anions) terminals. As the ion concentration in the base drops, I_C decreases. The transistor turns off to 10% of the value of the steady state on-current within ∼2 s, regardless of the duration of the on-state. The constant turn-off time indicates that ions are not accumulating to a significant extent inside the junction during the on-steady state but are instead constantly transported out of the junction. When all co-ions have been extracted from the junction, the Donnan exclusion prevents subsequent injection of anions into the base, and I_C is therefore low. The on/off ratio of I_C reaches above 100.A transfer curve was obtained by scanning V_EB between −3 and +3 V while keeping V_EC at 10 V (Figure 3(a)). As expected, both I_C and I_B remain low for negative V_EB. In this range, both EB and BC are biased in reverse direction. As V_EB turns positive, the EB configuration is switched into forward bias and ions are injected into the junction. This leads to a linear increase in I_C vs. V_EB. For the reverse scan, a minor hysteresis is observed for both the I_C and I_B scans, again probably due to the contribution of co-ion migration due to long time operation of the device.Open in a separate windowFIG. 3.Transfer and output curves. (a) The transfer curve is low for negative V_EB and increases linearly for positive V_EB with approximately zero threshold. (b) The output curves show I_C saturating with respect of V_EC for positive V_EB.The transistor output characteristics were obtained by scanning V_EC at different V_EB values (Figure 3(b)). The saturation regime, i.e., the bias mode was both EB and BC are in forward bias, was avoided as this has negative impact on the stability of the device. As reported for previous IBJT devices, the output characteristics show a clear saturation behaviour of I_C across the entire range of V_EC. Further, the I_C increases linearly with V_EB. The increase of both I_C and I_B when operating for extended periods of time in the active mode is again attributed to the addition and inclusion of co-ions in the junction. The current gain (I_C/I_B) at V_EC = 10 V decreases with V_EB and reaches 43.9, 17.9, and 10.7 for V_EB = 1 V, 2 V, and 3 V, respectively. For higher base bias voltages, the ion concentration increases in the junction and thus the injection selectivity decreases.In comparison with previously reported IBJTs,^12,14,21 the lack of a neutral electrolyte layer in the junction has an overall positive effect on the device characteristics. Main performance improvements are found in a decrease in the turn-on time from 9 s (for npn-IBJT²¹) to 2 s, for devices with comparable junction widths and heights. The main contribution to the improved switching speed is likely the decreased length between the emitter and collector. Interestingly, simulations have shown that an extended space charge region (ESCR), for a PEG-IBJT in cut-off mode, can extend several micrometers away from the collector.²² Thus, a PEG-IBJT with an emitter-collector separation of single micrometers should show an increased cut-off current due to the ESCR overlapping in the junction. However, by omitting the PEG in the junction, the ESCR is reduced due to screening from the fixed charges in the BM layers. This enables the IBJT, reported here, to operate with retained low cut-off currents. On-off ratios and ion current gains are approximately equal to previous IBJTs,^12,14,21 at above 100 and 10, respectively. The on–off ratio and ion current gain are more dependent on the selectivity of the membranes and the charge of the junction.Further, the need to separate the layers in a PEG-IBJT puts high demands on the patterning resolution and alignment accuracy to reduce the separation between emitter/collector and base. As polyphosphonium allows the IBJT to be built without separation of layers, miniaturization of the junction is relatively easier to obtain. The switching speed can potentially be further improved by retaining the base material between the emitter and collector (see Figure 1(b)), thus allowing for a more direct pathway for I_C. This design would, however, require a much more accurate layer alignment or that the base patterned on top of the emitter and collector layers. In general, such modifications of device geometry are simpler to accomplish with the non-EFE water dissociating polyphosphonium as fewer active layers are used, suggesting a further use of polyphosphonium to improve switching speed and miniaturization of IBJTs. Such further advancement in IBJT performance would be welcomed, for example, in the continued work towards complex ionic circuits¹⁴ to regulate signalling in bioelectronics and in drug delivery applications, in which generation of dynamic and complex gradients, at high spatial resolution, is of generic interest.  相似文献   

Dielectrophoresis based discrimination of human embryonic stem cells from differentiating derivatives     

Srinivas Velugotla  Steve Pells  Heidi K. Mjoseng  Cairnan R. E. Duffy  Stewart Smith  Paul De Sousa  Ronald Pethig 《Biomicrofluidics》2012,6(4)

Assessment of the dielectrophoresis (DEP) cross-over frequency (f_xo), cell diameter, and derivative membrane capacitance (C_m) values for a group of undifferentiated human embryonic stem cell (hESC) lines (H1, H9, RCM1, RH1), and for a transgenic subclone of H1 (T8) revealed that hESC lines could not be discriminated on their mean f_xo and C_m values, the latter of which ranged from 14 to 20 mF/m². Differentiation of H1 and H9 to a mesenchymal stem cell-like phenotype resulted in similar significant increases in mean C_m values to 41–49 mF/m² in both lines (p < 0.0001). BMP4-induced differentiation of RCM1 to a trophoblast cell-like phenotype also resulted in a distinct and significant increase in mean C_m value to 28 mF/m² (p < 0.0001). The progressive transition to a higher membrane capacitance was also evident after each passage of cell culture as H9 cells transitioned to a mesenchymal stem cell-like state induced by growth on a substrate of hyaluronan. These findings confirm the existence of distinctive parameters between undifferentiated and differentiating cells on which future application of dielectrophoresis in the context of hESC manufacturing can be based.  相似文献   

The effect of electron attachment on the ion mobility curves in the Zeleny air blast method of ion mobility measurement     

Leonard B. Loeb  Norris E. Bradbury 《Journal of The Franklin Institute》1932,213(2):181-194

In a recent paper Professor John Zeleny published curves obtained for ion mobilities at different ion ages in relatively pure N₂ using his classical air blast method. Two features are of especial interest; one the apparent gradual displacement of the negative ion peak to lower mobilities as the ion age increases and the other a marked asymmetry of the electron peak on the low mobility side. This Zeleny interprets as an unresolved negative ion mobility of value about 100 cm./sec. per volt/cm. Such a mobility can only be explained by a carrier that is ion part of its life and electron part of its life, the electronic and ionic phases alternating frequently. The writers indicate that the latter interpretation cannot be correct on the basis of the energies and probabilities involved in electron attachment. Analysis shows that the whole series of the observed phenomena in N₂ by this method are successfully accounted for on the proper application of the simplified theory of electron attachment to the air blast method. Since the attachment phenomena have to date not been applied to this type of mobility study it was felt of importance to present this analysis in order to guide future investigations by this method.  相似文献   

Li-ion battery material under high pressure: amorphization and enhanced conductivity of Li4Ti5O12     

Yanwei Huang  Yu He  Howard Sheng  Xia Lu  Haini Dong  Sudeshna Samanta  Hongliang Dong  Xifeng Li  Duck Young Kim  Ho-kwang Mao  Yuzi Liu  Heping Li  Hong Li  Lin Wang 《国家科学评论(英文版)》2019,6(2):239

Lithium titanium oxide (Li₄Ti₅O₁₂, LTO), a ‘zero-strain’ anode material for lithium-ion batteries, exhibits excellent cycling performance. However, its poor conductivity highly limits its applications. Here, the structural stability and conductivity of LTO were studied using in situ high-pressure measurements and first-principles calculations. LTO underwent a pressure-induced amorphization (PIA) at 26.9 GPa. The impedance spectroscopy revealed that the conductivity of LTO improved significantly after amorphization and that the conductivity of decompressed amorphous LTO increased by an order of magnitude compared with its starting phase. Furthermore, our calculations demonstrated that the different compressibility of the LiO₆ and TiO₆ octahedra in the structure was crucial for the PIA. The amorphous phase promotes Li⁺ diffusion and enhances its ionic conductivity by providing defects for ion migration. Our results not only provide an insight into the pressure depended structural properties of a spinel-like material, but also facilitate exploration of the interplay between PIA and conductivity.  相似文献   

Improving the dielectric properties of an electrowetting-on-dielectric microfluidic device with a low-pressure chemical vapor deposited Si3N4 dielectric layer     

Hsien-Hua Shen  Lung-Yuan Chung  Da-Jeng Yao 《Biomicrofluidics》2015,9(2)

Dielectric breakdown is a common problem in a digital microfluidic system, which limits its application in chemical or biomedical applications. We propose a new fabrication of an electrowetting-on-dielectric (EWOD) device using Si₃N₄ deposited by low-pressure chemical vapor deposition (LPCVD) as a dielectric layer. This material exhibits a greater relative permittivity, purity, uniformity, and biocompatibility than polymeric films. These properties also increase the breakdown voltage of a dielectric layer and increase the stability of an EWOD system when applied in biomedical research. Medium droplets with mouse embryos were manipulated in this manner. The electrical properties of the Si₃N₄ dielectric layer—breakdown voltage, refractive index, relative permittivity, and variation of contact angle with input voltage—were investigated and compared with a traditional Si₃N₄ dielectric layer deposited as a plasma-enhanced chemical vapor deposition to confirm the potential of LPCVD Si₃N₄ applied as the dielectric layer of an EWOD digital microfluidic system.  相似文献   

Integration of bio-inspired lanthanide-transition metal cluster and P-doped carbon nitride for efficient photocatalytic overall water splitting     

Rong Chen  Gui-Lin Zhuang  Zhi-Ye Wang  Yi-Jing Gao  Zhe Li  Cheng Wang  Yang Zhou  Ming-Hao Du  Suyuan Zeng  La-Sheng Long  Xiang-Jian Kong  Lan-Sun Zheng 《国家科学评论(英文版)》2021,8(9)

Photosynthesis in nature uses the Mn₄CaO₅ cluster as the oxygen-evolving center to catalyze the water oxidation efficiently in photosystem II. Herein, we demonstrate bio-inspired heterometallic LnCo₃ (Ln = Nd, Eu and Ce) clusters, which can be viewed as synthetic analogs of the CaMn₄O₅ cluster. Anchoring LnCo₃ on phosphorus-doped graphitic carbon nitrides (PCN) shows efficient overall water splitting without any sacrificial reagents. The NdCo₃/PCN-c photocatalyst exhibits excellent water splitting activity and a quantum efficiency of 2.0% at 350 nm. Ultrafast transient absorption spectroscopy revealed the transfer of a photoexcited electron and hole into the PCN and LnCo₃ for hydrogen and oxygen evolution reactions, respectively. A density functional theory (DFT) calculation showed the cooperative water activation on lanthanide and O−O bond formation on transition metal for water oxidation. This work not only prepares a synthetic model of a bio-inspired oxygen-evolving center but also provides an effective strategy to realize light-driven overall water splitting.  相似文献   

Mobilities of gaseous ions in CH₃NO₂H₂ and CH₃CNH₂ mixtures     

Elizabeth Ann Higley  Carolyn C. Thorsen 《Journal of The Franklin Institute》1933,215(1):69-80

Extending previous investigations by Loeb of mobilities in gaseous mixtures using his procedure except that the auxiliary field in these measurements was made equal to the advancing field thus giving absolute values of the mobilities, measurements of mobilities were made in mixtures of CH₃NO₂H2 and CH₃CNH₂. The mobilities in H₂ were 7.12 for the positive ions and 10.46 for the negative ions in cm./sec. per volt/cm. Those in CH₃NO₂ were 0.221 cm./sec. per volt/cm. for both ions and in CH₃CN they were 0.234 cm./sec. per volt/cm. for both ions. Both ion mobilities deviated from Blanc's law in CH₃NO₂ indicating the formation of complexes with the CH₃NO₂ ions somewhat greater in size than the normal ions in H₂. The molecules attached to negative ions somewhat less readily than to the positive ions but both final ions were of the same size. In CH₃CN mixtures both positive and negative ions deviated from Blanc's law, the positive ion showing more ready attachment of CH₃CN. The negative ion had consistently a higher mobility than the positive ion, a circumstance indicating a smaller ion and suggesting that the attaching molecule might not be CH₃CN but some impurity. Both ion addition products in CH₃CN are larger than the normal ion in H₂ but smaller than those in CH₃NO₂ as was to be expected.  相似文献   

Single nanopore transport of synthetic and biological polyelectrolytes in three-dimensional hybrid microfluidic∕nanofluidic devices     

Travis L. King  Enid N. Gatimu  Paul W. Bohn 《Biomicrofluidics》2009,3(1)

This paper presents a study of electrokinetic transport in single nanopores integrated into vertically stacked three-dimensional hybrid microfluidic∕nanofluidic structures. In these devices, single nanopores, created by focused ion beam (FIB) milling in thin polymer films, provide fluidic connection between two vertically separated, perpendicular microfluidic channels. Experiments address both systems in which the nanoporous membrane is composed of the same (homojunction) or different (heterojunction) polymer as the microfluidic channels. These devices are then used to study the electrokinetic transport properties of synthetic (i.e., polystyrene sulfonate and polyallylamine) and biological (i.e., DNA) polyelectrolytes across these nanopores using both electrical current measurements and confocal microscopy. Both optical and electrical measurements indicate that electro-osmotic transport is predominant over electrophoresis in single nanopores with d>180 nm, consistent with results obtained under similar conditions for nanocapillary array membranes.  相似文献   

Anisotropic alignments of hierarchical Li2SiO3/TiO2 @nano-C anode//LiMnPO4@nano-C cathode architectures for full-cell lithium-ion battery     

Hesham Khalifa  Sherif A El-Safty  Abdullah Reda  Mohamed A Shenashen  Alaa I Eid 《国家科学评论(英文版)》2020,7(5):863

We report on low-cost fabrication and high-energy density of full-cell lithium-ion battery (LIB) models. Super-hierarchical electrode architectures of Li₂SiO₃/TiO₂@nano-carbon anode (LSO.TO@nano-C) and high-voltage olivine LiMnPO₄@nano-carbon cathode (LMPO@nano-C) are designed for half- and full-system LIB-CR2032 coin cell models. On the basis of primary architecture-power-driven LIB geometrics, the structure keys including three-dimensional (3D) modeling superhierarchy, multiscale micro/nano architectures and anisotropic surface heterogeneity affect the buildup design of anode/cathode LIB electrodes. Such hierarchical electrode surface topologies enable continuous in-/out-flow rates and fast transport pathways of Li⁺-ions during charge/discharge cycles. The stacked layer configurations of pouch LIB-types lead to excellent charge/discharge rate, and energy density of 237.6 Wh kg⁻¹. As the most promising LIB-configurations, the high specific energy density of hierarchical pouch battery systems may improve energy storage for long-driving range of electric vehicles. Indeed, the anisotropic alignments of hierarchical electrode architectures in the large-scale LIBs provide proof of excellent capacity storage and outstanding durability and cyclability. The full-system LIB-CR2032 coin cell models maintain high specific capacity of ∼89.8% within a long-term life period of 2000 cycles, and average Coulombic efficiency of 99.8% at 1C rate for future configuration of LIB manufacturing and commercialization challenges.  相似文献   

Two-dimensional ferromagnetic superlattices     

Shanshan Liu  Ke Yang  Wenqing Liu  Enze Zhang  Zihan Li  Xiaoqian Zhang  Zhiming Liao  Wen Zhang  Jiabao Sun  Yunkun Yang  Han Gao  Ce Huang  Linfeng Ai  Ping Kwan Johnny Wong  Andrew Thye Shen Wee  Alpha T N&#x;Diaye  Simon A Morton  Xufeng Kou  Jin Zou  Yongbing Xu  Hua Wu  Faxian Xiu 《国家科学评论(英文版)》2020,7(4):745

Mechanically exfoliated two-dimensional ferromagnetic materials (2D FMs) possess long-range ferromagnetic order and topologically nontrivial skyrmions in few layers. However, because of the dimensionality effect, such few-layer systems usually exhibit much lower Curie temperature (T_C) compared to their bulk counterparts. It is therefore of great interest to explore effective approaches to enhance their T_C, particularly in wafer-scale for practical applications. Here, we report an interfacial proximity-induced high-T_C 2D FM Fe₃GeTe₂ (FGT) via A-type antiferromagnetic material CrSb (CS) which strongly couples to FGT. A superlattice structure of (FGT/CS)_n, where n stands for the period of FGT/CS heterostructure, has been successfully produced with sharp interfaces by molecular-beam epitaxy on 2-inch wafers. By performing elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally discovered that T_C of 4-layer Fe₃GeTe₂ can be significantly enhanced from 140 K to 230 K because of the interfacial ferromagnetic coupling. Meanwhile, an inverse proximity effect occurs in the FGT/CS interface, driving the interfacial antiferromagnetic CrSb into a ferrimagnetic state as evidenced by double-switching behavior in hysteresis loops and the XMCD spectra. Density functional theory calculations show that the Fe-Te/Cr-Sb interface is strongly FM coupled and doping of the spin-polarized electrons by the interfacial Cr layer gives rise to the T_C enhancement of the Fe₃GeTe₂ films, in accordance with our XMCD measurements. Strikingly, by introducing rich Fe in a 4-layer FGT/CS superlattice, T_C can be further enhanced to near room temperature. Our results provide a feasible approach for enhancing the magnetic order of few-layer 2D FMs in wafer-scale and render opportunities for realizing realistic ultra-thin spintronic devices.  相似文献   

Diatom-inspired multiscale mineralization of patterned protein–polysaccharide complex structures     

Ke Li  Yingfeng Li  Xinyu Wang  Mengkui Cui  Bolin An  Jiahua Pu  Jintao Liu  Boyang Zhang  Guijun Ma  Chao Zhong 《国家科学评论(英文版)》2021,8(8)

Marine diatoms construct their hierarchically ordered, three-dimensional (3D) external structures called frustules through precise biomineralization processes. Recapitulating the remarkable architectures and functions of diatom frustules in artificial materials is a major challenge that has important technological implications for hierarchically ordered composites. Here, we report the construction of highly ordered, mineralized composites based on fabrication of complex self-supporting porous structures—made of genetically engineered amyloid fusion proteins and the natural polysaccharide chitin—and performing in situ multiscale protein-mediated mineralization with diverse inorganic materials, including SiO₂, TiO₂ and Ga₂O₃. Subsequently, using sugar cubes as templates, we demonstrate that 3D fabricated porous structures can become colonized by engineered bacteria and can be functionalized with highly photoreactive minerals, thereby enabling co-localization of the photocatalytic units with a bacteria-based hydrogenase reaction for a successful semi-solid artificial photosynthesis system for hydrogen evolution. Our study thus highlights the power of coupling genetically engineered proteins and polysaccharides with biofabrication techniques to generate hierarchically organized mineralized porous structures inspired by nature.  相似文献   

Cascade-responsive nanobomb with domino effect for anti-tumor synergistic therapies     

Yang Liu  Yinghui Wang  Shuyan Song  Hongjie Zhang 《国家科学评论(英文版)》2022,9(3)

The development of reactive oxygen species (ROS) generation agents that can selectively produce sufficient ROS at the tumor site without external energy stimulation is of great significance for the further clinical application of ROS-based therapies. Herein, we designed a cascade-responsive ROS nanobomb (ZnO₂@Ce6/CaP@CPPO/BSA, designated as Z@Ce6/CaP@CB) with domino effect and without external stimulation for the specific generation of multiple powerful ROS storms at the tumor site. The calcium phosphate shell and ZnO₂ core gradually degrade and release Ca²⁺, Zn²⁺ and hydrogen peroxide (H₂O₂) under acid stimulation. On the one hand, Zn²⁺ can enhance the generation of endogenous superoxide anions (·O₂^–) and H₂O₂ through the inhibition of the mitochondrial electron transport chain. On the other hand, the generation of large amounts of exogenous H₂O₂ can cause oxidative damage to tumor cells and further activate bis[2,4,5-trichloro-6-(pentyloxycarbonyl)phenyl] oxalate (CPPO)-mediated chemiexcited photodynamic therapy. In addition, the oxidative stress caused by the generated ROS can lead to the uncontrolled accumulation of Ca²⁺ in cells and further result in Ca²⁺ overload-induced cell death. Therefore, the introduction of Z@Ce6/CaP@CB nanobombs triggered the ‘domino effect’ that caused multiple heavy ROS storms and Ca²⁺ overload in tumors and effectively activated anti-tumor immune response.  相似文献   

Superconductivity in chromium nitrides Pr3Cr10-xN11 with strong electron correlations     

Wei Wu  Kai Liu  Yanjie Li  Zhenhai Yu  Desheng Wu  Yuting Shao  Shihang Na  Gang Li  Ruizhen Huang  Tao Xiang  Jianlin Luo 《国家科学评论(英文版)》2020,7(1):21

Exploration of superconductivity in Cr-based compounds has attracted considerable interest because only a few Cr-based superconductors (CrAs, A₂Cr₃As₃ and ACr₃As₃ (A = K, Rb, Cs, Na)) have been discovered so far and they show an unconventional pairing mechanism. We report the discovery of bulk superconductivity at 5.25 K in chromium nitride in Pr₃Cr_10-xN₁₁ with a cubic lattice structure. A relatively large upper critical field of H_c2(0) ∼ 12.6 T is determined, which is larger than the estimated Pauli-paramagnetic pair-breaking magnetic field. The material has a large electronic specific-heat coefficient of 170 mJ K⁻² mol⁻¹—about 10 times larger than that estimated by the electronic structure calculation, which suggests that correlations between 3d electrons are very strong in Pr₃Cr_10-xN₁₁, and thus quantum fluctuations might be involved. Electronic structure calculations show that the density of states at the Fermi energy are contributed predominantly by Cr 3d electrons, implying that the superconductivity results mainly from the condensation of Cr 3d electrons. Pr₃Cr_10-xN₁₁ represents a rare example of possible unconventional superconductivity emerging in a 3D system with strong electron correlations. Nevertheless, clarification of the specific pairing symmetry needs more investigation.  相似文献   

Screening ion-channel ligand interactions with passive pumping in a microfluidic bilayer lipid membrane chip     

Shimul C. Saha  Andrew M. Powl  B. A. Wallace  Maurits R. R. de Planque  Hywel Morgan 《Biomicrofluidics》2015,9(1)

We describe a scalable artificial bilayer lipid membrane platform for rapid electrophysiological screening of ion channels and transporters. A passive pumping method is used to flow microliter volumes of ligand solution across a suspended bilayer within a microfluidic chip. Bilayers are stable at flow rates up to ∼0.5 μl/min. Phospholipid bilayers are formed across a photolithographically defined aperture made in a dry film resist within the microfluidic chip. Bilayers are stable for many days and the low shunt capacitance of the thin film support gives low-noise high-quality single ion channel recording. Dose-dependent transient blocking of α-hemolysin with β-cyclodextrin (β-CD) and polyethylene glycol is demonstrated and dose-dependent blocking studies of the KcsA potassium channel with tetraethylammonium show the potential for determining IC₅₀ values. The assays are fast (30 min for a complete IC₅₀ curve) and simple and require very small amounts of compounds (100 μg in 15 μl). The technology can be scaled so that multiple bilayers can be addressed, providing a screening platform for ion channels, transporters, and nanopores.  相似文献   

Altering the rate-determining step over cobalt single clusters leading to highly efficient ammonia synthesis     

Sisi Liu  Mengfan Wang  Haoqing Ji  Xiaowei Shen  Chenglin Yan  Tao Qian 《国家科学评论(英文版)》2021,8(5)

Activation of high-energy triple-bonds of N₂ is the most significant bottleneck of ammonia synthesis under ambient conditions. Here, by importing cobalt single clusters as strong electron-donating promoter into the catalyst, the rate-determining step of ammonia synthesis is altered to the subsequent proton addition so that the barrier of N₂ dissociation can be successfully overcome. As revealed by density functional theory calculations, the N₂ dissociation becomes exothermic over the cobalt single cluster upon the strong electron backdonation from metal to the N₂ antibonding orbitals. The energy barrier of the positively shifted rate-determining step is also greatly reduced. At the same time, advanced sampling molecular dynamics simulations indicate a barrier-less process of the N₂ approaching the active sites that greatly facilitates the mass transfer. With suitable thermodynamic and dynamic property, a high ammonia yield rate of 76.2 μg h^–1 mg and superior Faradaic efficiency of 52.9% were simultaneously achieved.  相似文献   

Direct transformation of dinitrogen: synthesis of N-containing organic compounds via N−C bond formation     

Ze-Jie Lv  Junnian Wei  Wen-Xiong Zhang  Ping Chen  Dehui Deng  Zhang-Jie Shi  Zhenfeng Xi 《国家科学评论(英文版)》2020,7(10):1564

N-containing organic compounds are of vital importance to lives. Practical synthesis of valuable N-containing organic compounds directly from dinitrogen (N₂), not through ammonia (NH₃), is a holy-grail in chemistry and chemical industry. An essential step for this transformation is the functionalization of the activated N₂ units/ligands to generate N−C bonds. Pioneering works of transition metal-mediated direct conversion of N₂ into organic compounds via N−C bond formation at metal-dinitrogen [N₂-M] complexes have generated diversified coordination modes and laid the foundation of understanding for the N−C bond formation mechanism. This review summarizes those major achievements and is organized by the coordination modes of the [N₂-M] complexes (end-on, side-on, end-on-side-on, etc.) that are involved in the N−C bond formation steps, and each part is arranged in terms of reaction types (N-alkylation, N-acylation, cycloaddition, insertion, etc.) between [N₂-M] complexes and carbon-based substrates. Additionally, earlier works on one-pot synthesis of organic compounds from N₂ via ill-defined intermediates are also briefed. Although almost all of the syntheses of N-containing organic compounds via direct transformation of N₂ so far in the literature are realized in homogeneous stoichiometric thermochemical reaction systems and are discussed here in detail, the sporadically reported syntheses involving photochemical, electrochemical, heterogeneous thermo-catalytic reactions, if any, are also mentioned. This review aims to provide readers with an in-depth understanding of the state-of-the-art and perspectives of future research particularly in direct catalytic and efficient conversion of N₂ into N-containing organic compounds under mild conditions, and to stimulate more research efforts to tackle this long-standing and grand scientific challenge.  相似文献   

Polyphosphonium‐based bipolar membranes for rectification of ionic currents     

Erik O. Gabrielsson  Magnus Berggren 《Biomicrofluidics》2013,7(6)

Bipolar membranes (BMs) have interesting applications within the field of bioelectronics, as they may be used to create non-linear ionic components (e.g., ion diodes and transistors), thereby extending the functionality of, otherwise linear, electrophoretic drug delivery devices. However, BM based diodes suffer from a number of limitations, such as narrow voltage operation range and/or high hysteresis. In this work, we circumvent these problems by using a novel polyphosphonium-based BM, which is shown to exhibit improved diode characteristics. We believe that this new type of BM diode will be useful for creating complex addressable ionic circuits for delivery of charged biomolecules.Combined electronic and ionic conduction makes organic electronic materials well suited for bioelectronics applications as a technological mean of translating electronic addressing signals into delivery of chemicals and ions.¹ For complex regulation of functions in cells and tissues, a chemical circuit technology is necessary in order to generate complex and dynamic signal gradients with high spatiotemporal resolution. One approach to achieve a chemical circuit technology is to use bipolar membranes (BMs), which can be used to create the ionic equivalents of diodes^{2, 3, 4, 5} and transistors.^{6, 7, 8} A BM consists of a stack of a cation- and an anion-selective membrane, and functions similar to the semiconductor PN-junction, i.e., it offers ionic current rectification^{9, 10} (Figure ​(Figure1a).1a). The high fixed charge concentration in a BM configuration make them more suited in bioelectronic applications as compared to other non-linear ionic devices, such as diodes constructed from surface charged nanopores¹¹ or nanochannels,¹² as the latter devices typically suffers from reduced performance at elevated electrolyte concentration (i.e., at physiological conditions) due to reduced Debye screening length.¹³ However, a unique property of most BMs, as compared to the electronic PN-junction and other ionic diodes, is the electric field enhanced (EFE) water dissociation effect.^{10, 14} This occurs above a threshold reverse bias voltage, typically around −1 V, as the high electric field across the ion-depleted BM interface accelerates the forward reaction rate of the dissociation of water into H⁺ and OH⁻ ions. As these ions migrate out from the BM, there will be an increase in the reverse bias current. The EFE water dissociation is a very interesting effect and is commonly used in industrial electrodialysis applications,¹⁵ where highly efficient water dissociating BMs are being researched.¹⁶ Also, BMs have also been utilized to generate H⁺ and OH⁻ ions in lab-on-a-chip applications.^{2, 17} However, the EFE water dissociation effect diminishes the diode property of BMs when operated outside the ±1 V window, which is unwanted in, for instance, chemical circuits and addressing matrices for delivery of complex gradients of chemical species. The effect can be suppressed by incorporating a neutral electrolyte inside the BM,^{10, 18} for instance, poly(ethylene glycol) (PEG).^{2, 6, 7} However, as previously reported,² the PEG volume will introduce hysteresis when switching from forward to reverse bias, due to its ability to store large amounts of charges. This was circumvented by ensuring that only H⁺ and OH⁻ are present in the diode, which recombines into water within the PEG volume. Such diodes are well suited as integrated components in chemical circuits for pH-regulation, due to the in situ formed H⁺ and OH⁻, but are less attractive if, for instance, other ions, e.g., biomolecules, are to be processed or delivered in and from the circuit. Furthermore, a PEG electrolyte introduces additional patterning layers, making device downscaling more challenging. This is undesired when designing complex, miniaturized, and large-scale ionic circuits. Thus, there is an interest in BM diodes that intrinsically do not exhibit any EFE water dissociation, are easy to miniaturize, and that turn off at relatively high speeds. It has been suggested that tertiary amines in the BM interface are important for efficient EFE water dissociation,^{19, 20, 21} as they function as a weak base and can therefore catalyze dissociation of water by accepting a proton. For example, anion-selective membranes that have undergone complete methylation, converting all tertiary amines to quaternary amines, shows no EFE water dissociation,¹⁹ although this effect was not permanent, as the quaternization was reversed upon application of a current. Similar results were found for anion-selective membranes containing alkali-metal complexing crown ethers as fixed charges.²¹ Also, EFE water dissociation was not observed or reduced in BMs with poor ion selectivity, for example, in BMs with low fixed-charge concentration⁵ or with predominantly secondary and tertiary amines in the anion-selective membrane,²² as the increased co-ion transport reduces the electric field at the BM interface. However, due to decreased ion selectivity, these membranes show reduced rectification. In this work, we present a non-amine based BM diode that avoids EFE water dissociation, enables easy miniaturization, and provides fast turn-off speeds and high rectification.Open in a separate windowFigure 1(a) Ionic current rectification in a BM. In forward bias, mobile ions migrate towards the interface of the BM. The changing ion selectivity causes ion accumulation, resulting in high ion concentration and high conductivity. At high ion concentration, the selectivity of the membranes fails (Donnan exclusion failure), and ions start to pass the BM. In reverse bias, the mobile ions migrate away from the BM, eventually giving a zone with low ion concentration and low conductivity. Reverse bias can cause EFE water dissociation, producing H⁺ and OH^- ions. (b) Chemical structures of PSS, qPVBC, and PVBPPh₃. (c) The device used to characterize the BMs and the BM1A, BM2A, and BM1P designs. The BM interfaces are 50 × 50 μm.An anion-selective phosphonium-based polycation (poly(vinylbenzyl chloride) (PVBC) quaternized by triphenylphospine, PVBPPh₃) was synthesized and compared to the ammonium-based polycation (PVBC quaternized by dimethylbenzylamine, qPVBC) previously used in BM diodes² and transistors,^{7, 8} when included in BM diode structures together with polystyrenesulfonate (PSS) as the cation-selective material (Figure ​(Figure1b).1b). Three types of BM diodes were fabricated using standard photolithography patterning (Figure ​(Figure1c),1c), either with qPVBC (BM1A and BM2A) or PVBPPh₃ (BM1P) as polycation and either with (BM2A) or without PEG (BM1A and BM1P). Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrodes covered with aqueous electrolytes were used to convert electronic input signals into ionic currents through the BMs, according to the redox reaction PEDOT⁺:PSS⁻ + M⁺ + e⁻ ↔ PEDOT⁰ + M⁺:PSS⁻.The rectifying behavior of the diodes was evaluated using linear sweep voltammetry (Figure ​(Figure2).2). The BM1A diode exhibited an increase in the reverse bias current for voltages lower than −1 V, a typical signature of EFE water dissociation,^{10, 14} which decreased the current rectification at ±4 V to 6.14. No such deviation in the reverse bias current was observed for BM2A and BM1P, which showed rectification ratios of 751 and 196, respectively. In fact, for BM1P, no evident EFE water dissociation was observed even at −40 V (see inset of Figure ​Figure2).2). Thus, the PVBPPh₃ polycation allows BM diodes to operate at voltages beyond the ±1 V window with maintained high ion current rectification.Open in a separate windowFigure 2Linear sweep voltammetry from −4 to +4 V (25 mV/s) for the BM diodes. The inset shows BM1P scanning from −40 V to +4 V (250 mV/s).The dynamic performance of the diodes was tested by applying a square wave pulse from reverse bias to a forward bias voltage of 4 V with 5–90 s pulse duration (Figure ​(Figure3).3). To access the amount of charge injected and extracted during the forward bias and subsequent turn off, the current through the device was integrated. For BM2A, we observed that the fall time increased with the duration of the forward bias pulse. This hysteresis is due to the efficient storage of ions in the large PEG volume, with no ions crossing the BM due to Donnan exclusion failure.² As a result, during the initial period of the return to reverse bias, a large amount of charge needs to be extracted in order to deplete the BM. After a 90 s pulse, 90.6% of the injected charge during the forward bias was extracted before turn-off. This may be contrasted with BM1P, where the fall time is hardly affected by the pulse duration, and the extracted/injected ratio is only 15.4% for a 90 s pulse. For this type of BM, the interface quickly becomes saturated with ions during forward bias, leading to Donnan exclusion failure and transport of ions across the BM.⁴ Thus, less charge needs to be extracted to deplete the BM, allowing for faster fall times and significantly reduced hysteresis.Open in a separate windowFigure 3Switching characteristics (5, 10, 20, 30, 60, or 90 s pulse) and ion accumulation (at 90 s pulse) of the BM2A and BM1P diodes. BM1A showed similar characteristics as BM1P when switched at ±1V (see supplementary material).²⁴Since the neutral electrolyte is no longer required to obtain high ion current rectification over a wide potential range, the size of the BM can be miniaturized. This translates into higher component density when integrating the BM diode into ionic/chemical circuits. A miniaturized BM1P diode was constructed, where the interface of the BM was shrunk from 50 μm to 10 μm. The 10 μm device showed similar IV and switching characteristics as before (Figure ​(Figure4),4), but with higher ion current rectification ratio (over 800) and decreased rise/fall times (corresponding to 90%/–10% of forward bias steady state) from 10 s/12.5 s to 4 s/4 s. Since the overlap area is smaller, a probable reason for the faster switching times is the reduced amount of ions needed to saturate and deplete the BM interface. In comparison to our previous reported low hysteresis BM diode,² this miniaturized polyphosphonium-based devices shows the same rise and fall times but increased rectification ratio.Open in a separate windowFigure 4(a) Linear sweep voltammetry and (b) switching performance of a BM1P diode with narrow junction.In summary, by using polyphosphonium instead of polyammonium as the polycation in BM ion diodes the EFE water dissociation can be entirely suppressed over a large operational voltage window, supporting the theory that a weak base, such as a tertiary amine, is needed for efficient EFE water dissociation.^{17, 18} As no additional neutral layer at the BM interface is needed, ion diodes that operate outside the usual EFE water dissociation window of ±1 V can be constructed using less active layers, fewer processing steps and with relaxed alignment requirement as compared to polyammonium-based devices. This enables the fabrication of ion rectification devices with an active interface as low as 10 μm. Furthermore, the exclusion of a neutral layer improves the overall dynamic performance of the BM ion diode significantly, as there is less hysteresis due to ion accumulation. Previously, the hysteresis of BM ion diodes has been mitigated by designing the diode so that only H⁺ and OH⁻ enters the BM, which then recombines into water.² Such diodes also show high ion current rectification ratio and switching speed but are more complex to manufacture, and their application in organic bioelectronic systems is limited due to the H⁺/OH⁻ production. By instead using the polyphosphonium-based BM diode, reported here, we foresee ionic, complex, and miniaturized circuits that can include charged biomolecules as the signal carrier to regulate functions and the physiology in cell systems, such as in biomolecule and drug delivery applications, and also in lab-on-a-chip applications.  相似文献   

Exposed facet-controlled N2 electroreduction on distinct Pt3Fe nanostructures of nanocubes,nanorods and nanowires     

Wu Tong  Bolong Huang  Pengtang Wang  Qi Shao  Xiaoqing Huang 《国家科学评论(英文版)》2021,8(1)

Understanding the correlation between exposed surfaces and performances of controlled nanocatalysts can aid effective strategies to enhance electrocatalysis, but this is as yet unexplored for the nitrogen reduction reaction (NRR). Here, we first report controlled synthesis of well-defined Pt₃Fe nanocrystals with tunable morphologies (nanocube, nanorod and nanowire) as ideal model electrocatalysts for investigating the NRR on different exposed facets. The detailed electrocatalytic studies reveal that the Pt₃Fe nanocrystals exhibit shape-dependent NRR electrocatalysis. The optimized Pt₃Fe nanowires bounded with high-index facets exhibit excellent selectivity (no N₂H₄ is detected), high activity with NH₃ yield of 18.3 μg h⁻¹ mg⁻¹_cat (0.52 μg h⁻¹ cm⁻²_ECSA; ECSA: electrochemical active surface area) and Faraday efficiency of 7.3% at −0.05 V versus reversible hydrogen electrode, outperforming the {200} facet-enclosed Pt₃Fe nanocubes and {111} facet-enclosed Pt₃Fe nanorods. They also show good stability with negligible activity change after five cycles. Density functional theory calculations reveal that, with high-indexed facet engineering, the Fe-3d band is an efficient d-d coupling correlation center for boosting the Pt 5d-electronic exchange and transfer activities towards the NRR.  相似文献