Molecular-level proton acceptor boosts oxygen evolution catalysis to enable efficient industrial-scale water splitting

Industrial water splitting has long been suppressed by the sluggish kinetics of the oxygen evolution reaction(OER),which requires a catalyst to be efficient.Herein,we propose a molecular-level proton acceptor strategy to produce an efficient OER catalyst that can boost industrial-scale water splitting.Molecular-level phosphate(-PO_(4))group is introduced to modify the surface of PrBa_(0.5)Ca_(0.5)Co_(2)O_(5)+δ(PBCC).The achieved catalyst(PO_(4)-PBCC)exhibits significantly enhanced catalytic performance in alkaline media.Based on the X-ray absorption spectroscopy results and density functional theory(DFT)calculations,the PO_(4)on the surface,which is regarded as the Lewis base,is the key factor to overcome the kinetic limitation of the proton transfer process during the OER.The use of the catalyst in a membrane electrode assembly(MEA)is further evaluated for industrial-scale water splitting,and it only needs a low voltage of 1.66 V to achieve a large current density of 1 A cm^(-2).This work provides a new molecular-level strategy to develop highly efficient OER electrocatalysts for industrial applications.

Tensile Properties and Wear Resistance of Mg Alloy Containing High Si as Implant Materials

Magnesium alloy has been considered as one of the third-generation biomaterials for the regeneration and support of functional bone tissue.As a regeneration implant material with great potential applications,in-situ Mg_(2)Si phase reinforced Mg-6Zn cast alloy was comprehensively studied and expected to possess excellent mechanical properties via the refining and modifying of Mg_(2)Si reinforcements.The present study demonstrates that the primary and eutectic Mg_(2)Si phase can be greatly modified by the yttrium(Y)addition.The size of the primary Mg_(2)Si phases can be reduced to~20μm with an addition of 0.5 wt.%Y.This phenomenon is mainly attributed to the poisoning effect of the Y element.Moreover,wear resistance and tensile properties of the ternary alloy have also been improved by the Y addition.Mg-6Zn-4Si-0.5Y alloy exhibits optimal tensile properties and wears resistance.The ultimate tensile strength and the elongation of the alloy with 0.5 wt.%Y are 50%and 65%higher than those of the ternary alloy,respectively.Excessive Y addition(1.0 wt.%)deteriorates the tensile properties of Mg-Zn-Si alloy.The improvement of the tensile properties is mainly due to the modification of primary and eutectic Mg_(2)Si phases as well as the solid solution strengthening of the Y atoms.This study provides a certain implication for the application of Mg-Zn-Si alloys containing Y elements as regeneration implants.

Growth of high quality Sr2IrO4 epitaxial thin films on conductive substrates

Ruddlesden–Popper iridium oxides have attracted considerable interest because of the many proposed novel quantum states that arise from the large spin–orbit coupling of the heavy iridium atoms in them.A prominent example is the single layer Sr2IrO4, in which superconductivity has been proposed under electron doping.However, the synthesis of Sr2IrO4 high quality thin films has been a huge challenge due to the easy formation of impurities associated with different numbers of SrO layers.Thus techniques to optimize the growth of pure phase Sr2IrO4 are urgently required.Here we report the deposition of high quality Sr2IrO4 thin films on both insulating SrTiO3 and conducting SrTiO3:Nb substrates using pulsed laser deposition assisted with reflective high-energy electron diffraction.The optimal deposition temperature of Sr2IrO4 epitaxial films on SrTiO3:Nb substrates is about 90℃ lower than that on SrTiO3 substrates.The electrical transports of high quality Sr2IrO4 films are measured, which follow the three-dimensional Mott variable-range hopping model.The film magnetizations are measured, which show weak ferromagnetism below ~240 K with a saturation magnetization of~ 0.2 μB/Ir at 5 K.This study provides applicable methods to prepare high quality 5 d Sr2IrO4 epitaxial films, which could be extended to other Ruddlesden–Popper phases and potentially help the future study of exotic quantum phenomena in them.

Phenylformamidinium-enabled quasi-2D Ruddlesden-Popper perovskite solar cells with improved stability

Two-dimensional(2D)/quasi-2D perovskite solar cells(PSCs)incorporating organic spacer cations exhibit appealing ambient stability in comparison with their 3D analogs.Most reported organic spacer cations are based on ammonium,whereas formamidinium(FA^(+))has been seldom applied despite that FA has been extensively used in high-efficiency 3D PSCs.Herein,a novel FA-based organic spacer cation,4-chloro-phenylformamidinium(CPFA^(+)),is applied in quasi-2D Ruddlesden-Popper(RP)PSCs for the first time,and methylammonium chloride(MACl)is employed to promote crystal growth and orientation of perovskite film,resulting in high power conversion efficiency(PCE)with improved stability.Upon incorporating CPFA+organic spacer cation and MACl additive,high-quality quasi-2D CPFA_(2)MA_(n-1)Pb_(n)(I_(0.857)Cl_(0.143))_(3n+1)(n=9)perovskite film forms,exhibiting improved crystal orientation,reduced trap state density,prolonged carrier lifetime and optimized energy level alignment.Consequently,the CPFA_(2)MA_(n-1)Pb_(n)(I_(0.857)Cl_(0.143))_(3n+1)(n=9)quasi-2D RP PSC devices deliver a highest PCE of 14.78%.Moreover,the un-encapsulated CPFA-based quasi-2D RP PSC devices maintain~80%of its original PCE after exceeding 2000 h storage under ambient condition,whereas the 3D MAPb I3counterparts retain only~45%of its original PCE.Thus,the ambient stability of quasi-2D RP PSC devices is improved obviously relative to its 3D MAPb I3counterpart.

Magnetic anisotropy manipulation and interfacial coupling in Sm_(3)Fe_(5)O_(12)films and CoFe/Sm_(3)Fe_(5)O_(12)heterostructures

The magnetic anisotropy manipulation in the Sm_(3)Fe_(5)O_(12)(SmIG)films and its effect on the interfacial spin coupling in the CoFe/SmIG heterostructures were studied carefully.By switching the orientation of the Gd_(3)Ga_(5)O_(12)substrates from(111)to(001),the magnetic anisotropy of obtained SmIG films shifts from in-plane to out-of-plane.Similar results can also be obtained in the films on Gd_(3)Ga_(5)O_(12)substrates,which identifies the universality of such orientation-induced magnetic anisotropy switching.Additionally,the interfacial spin coupling and magnetic anisotropy switching effect on the spin wave in CoFe/SmIG magnetic heterojunctions have also been explored by utilizing the time-resolved magneto-optical Kerr effect technique.It is intriguing to find that both the frequency and effective damping factor of spin precession in CoFe/SmIG heterojunctions can be manipulated by the magnetic anisotropy switching of SmIG films.These findings not only provide a route for the perpendicular magnetic anisotropy acquisition but also give a further path for spin manipulation in magnetic films and heterojunctions.

Growth and transport properties of topological insulator Bi2Se3 thin film on a ferromagnetic insulating substrate

Exchange coupling between topological insulator and ferromagnetic insulator through proximity effect is strongly attractive for both fundamental physics and technological applications. Here we report a comprehensive investigation on the growth behaviors of prototype topological insulator Bi2Se3 thin film on a single-crystalline LaCoO3 thin film on SrTiO3 substrate, which is a strain-induced ferromagnetic insulator. Different from the growth on other substrates, the Bi2Se3 films with highest quality on LaCoO3 favor a relatively low substrate temperature during growth. As a result, an inverse dependence of carrier mobility with the substrate temperature is found. Moreover, the magnetoresistance and coherence length of weak antilocalization also have a similar inverse dependence with the substrate temperature, as revealed by the magnetotransport measurements. Our experiments elucidate the special behaviors in Bi2Se3/LaCoO3 heterostructures, which provide a good platform for exploring related novel quantum phenomena, and are inspiring for device applications.

范德华材料Ta_(2)Ni_(3)Te_(5)中巨大的面内振动和输运各向异性

目前,Ta_(2)M3Te_(5)(M=Ni,Pd)层状范德华化合物可承载各种奇异电子态,且具有表现出非平凡输运现象的诱人潜力,因而重新引起人们的兴趣.其特征有Luttinger液体、量子自旋霍尔效应、高阶拓扑结构和超导电性.本文中,我们报道了单晶Ta_(2)Ni_(3)Te_(5)的合成,并揭示了其在每个具有准一维键合特征的层内的多重平面内各向异性.我们的技术结合了偏振拉曼光谱、角度分辨光电发射光谱、第一性原理计算和电/磁输运测量的能力.链状低对称层状结构的声子振动产生了高度各向异性的拉曼响应,不同的链内和链间键合特性导致电子带和声学声子的各向异性色散,这共同导致[100]和[001]方向之间的巨大平面内迁移率各向异性(2000%).这一结果与我们的电输运和霍尔效应测量结果相符.因此,沿不同平面内方向的输运行为也表现出不同的温度和磁场依赖性.本工作揭示的丰富的面内各向异性表明,Ta_(2)Ni_(3)Te_(5)是探索新型二维各向异性电子动力学的一个很有前途的平台,在下一代纳米电子器件中具有潜在的应用前景.

Larger in-plane upper critical field and superconducting diode effect observed in topological superconductor candidate InNbS_(2)nanoribbons

Recently,the coexistence of topology and superconductivity has garnered considerable attention.Specifically,the dimensionality of these materials is crucial for the realization of topological quantum computation.However,the naturally grown materials,especially with one-dimensional feature that exhibits the coexistence of topology and superconductivity,still face challenges in terms of experimental realization and scalability,which hinders the fundamental research development and the potential to revolutionize quantum computing.Here,we report the first experimental synthesis of quasi-one-dimensional InNbS_(2)nanoribbons that exhibit the coexistence of topological order and superconductivity via a chemical vapor transport method.Especially,the inplane upper critical field of InNbS_(2)nanoribbons exceeds the Pauli paramagnetic limit by more than 2.2 times,which can be attributed to the enhanced spin-orbit coupling and the weakened interlayer interaction between the NbS_(2)layers induced by the insertion of In atoms,making InNbS_(2)exhibit spin-momentum locking similar to that of monolayer NbS_(2).Moreover,for the first time,we report the superconducting diode effect in a quasi-one-dimensional superconductor system without any inherent geometric imperfections.The measured maximum efficiency is manifested as 14%,observed atμ0H≈±60 mT,and we propose that the superconducting diode effect can potentially be attributed to the presence of the nontrivial topological band.Our work provides a platform for studying exotic phenomena in condensed matter physics and potential applications in quantum computing and quantum information processing.

电场可逆调控二维单层氧化物磁电性能研究

具有原子层厚度的氧化物磁性材料拥有将二维磁性应用到下一代自旋电子学新兴领域的巨大潜力,引起了研究者的广泛关注.因此,实现二维单层氧化物磁、电性能的磁场和电场调控,为未来低功耗自旋电子器件提供了广阔应用前景.然而,电场调控二维单层氧化物磁性报道很少.本工作利用离子液体门电压进行质子掺杂,实现了对二维单层氧化物(SrRuO_(3))_(1)/(SrTiO_(3))_(N)(N=1,3)磁、电性能的电场可逆调控.随着质子掺杂浓度提高,在(SrRuO_(3))_(1)/(SrTiO_(3))_(1)中观察到了从铁磁金属到反铁磁绝缘态相变,并伴随着磁各向异性的转变.理论分析表明,质子掺杂引起的能带结构改变是结构和磁、电性能相变的主要原因.同时,SrTiO_(3)层起到质子筛作用,在质子的演化过程中扮演重要角色.该研究通过电场调控二维单层氧化物的结构和物性,为实现材料的多功能性提供了重要思路,同时也为实现低功耗功能器件提供了应用潜力.

Synchronous defect passivation of all-inorganic perovskite solar cells enabled by fullerene interlayer

All-inorganic CsPbI_(3-x)Br_(x)perovskite solar cells(PSCs)are advantageous in terms of high thermal stability,while its efficiency lags behind those of organic-inorganic hybrid perovskite counterparts.Defect passivations have been extensively applied for enhancing efficiency of all-inorganic PSCs,which are mainly based on univocal defect passivation of perovskite layer.Herein,we incorporated a bis-dimethylamino-functionalized fullerene derivative(abbreviated as PCBDMAM)as an interlayer between ZnO electron transport layer(ETL)and all-inorganic CsPbI_(2.25)Br_(0.75)perovskite layer,accomplishing synchronous defect passivations of both layers and consequently dramatic enhancements of efficiency and thermal stability of PSC devices.Upon spin-coating PCBDMAM onto ZnO ETL,the surface defects of ZnO especially oxygen vacancies can be effectively passivated due to the formation of Zn−N ionic bonds.In addition,PCBDMAM incorporation affords effective passivation of Pb_(I)and I_(Pb)antisite defects within the atop perovskite layer as well via coordination bonding with Pb^(2+).As a result,the regular-structure planar CsPbI_(2.25)Br_(0.75)PSC device delivers a champion power conversion efficiency(PCE)of 17.04%,which surpasses that of the control device(15.44%).Moreover,the PCBDMAM-incorporated PSC device maintains~80%of its initial PCE after 600 h heating at 85°C hot plate in N2 atmosphere,whereas PCE of the control device degrades rapidly to~62%after 460 h heating under identical conditions.Hence,PCBDMAM incorporation benefited dramatic improvement of the thermal stability of PSC device.

Ultrafast control of slow light in THz electromagnetically induced transparency metasurfaces

In this paper,we experimentally demonstrate ultrafast optical control of slow light in the terahertz(THz) range by combining the electromagnetically induced transparency(EIT) metasurfaces with the cut wire made of P+-implanted silicon with short carrier lifetime.Employing the optical-pump THz-probe spectroscopy,we observed that the device transited from a state with a slow light effect to a state without a slow light effect in an ultrafast time of 5 ps and recovered within 200 ps.A coupled oscillator model is utilized to explain the origin of controllability.The experimental results agree very well with the simulated and theoretical results.These EIT metasurfaces have the potential to be used as an ultrafast THz optical delay device.

Thermoelectric properties of In-Hg co-doping in SnTe:Energy band engineering

Synergistic effect of band convergence and resonant level could be manipulated in SnTe by co-doping In and Hg,leading to a potential thermoelectric performance enhancement in a much wider temperature range.In this work we carefully investigated thermoelectric properties of the In-Hg co-doped SnTe,synthesized by a hot pressing method.With this co-doping the Seebeck coefficients of the co-doped samples were greatly improved(over 50 mVK^(-1))at the room temperature.Although power factors of the In-Hg co-doped SnTe were also able to be optimized,the peak ZT(0.9 at 850 K in Sn_(0.98)Bi_(0.02)Te-1%HgInTe_(2)),however,is not high enough when comparing to other co-doped SnTe systems.This may be caused by the relatively high lattice thermal conductivity.An apparent competition between band convergence doping and resonant level doping was observed in our experiment.The results suggest that band engineering via co-doping should be further understood in order to optimize the thermoelectric properties inside the material system.

Pomegranate-like C_(60)@cobalt/nitrogen-codoped porous carbon for high-performance oxygen reduction reaction and lithium-sulfur battery

Porous carbon materials play essential roles in electrocatalysis and electrochemical energy storage.It is of significant importance to rationally design and tune their porous structure and active sites for achieving high electrochemical activity and stability.Herein,we develop a novel approach to tune the morphology of porous carbon materials(PCM)by embedding fullerene C_(60),achieving improved performance of oxygen reduction reaction(ORR)and lithium-sulfur(Li-S)battery.Owing to the strong interaction between C_(60)and imidazole moieties,pomegranate-like hybrid of Ow-embedded zeolitic imidazolate framework(ZIF-67)precursor is synthesized,which is further pyrolyzed to form C_(60)-embedded cobalt/nitrogen-codoped porous carbon materials(abbreviated as C_(60)@Co-N-PCM).Remarkably,the unique structure of C_(60)@Co-N-PCM offers excellent ORR electrocatalytic activity and stability in alkaline solutions,outperforming the commercial Pt/C(20 wt.%)catalyst.Besides,C_(60)@Co-N-PCM as a novel cathode delivers a high specific capacity of-900 mAh·g^(-1) at 0.2 C rate in Li-S batteries,which is superior to the pristine ZIF-67-derived PCM without embedding C_(60).

Ferromagnetic and ferroelectric properties of Aurivillius phase Bi_9Fe_(4.7)Me_(0.3)Ti_3O_(27)(Me 5 Fe, Co, Ni, Mn)

New Aurivillius phase Bi9Fe4.7Me0.3Ti3O27(Me = Fe, Co, Ni, Mn) oxides have been prepared using a citrate combustion method. X-ray diffraction on powders and high-resolution transmission electron microscopy investigation confirmed that the Bi9Fe4.7Me0.3Ti3O27 samples are with an eight-layer structure. Both ferromagnetic and ferroelectric investigations suggested that Co or Ni substitution could enhance their multiferroic properties,while Mn substitution depressed them. Among all the samples, Bi9Fe4.7Co0.3Ti3O27 sample exhibits the largest remnant polarization of Pr*3.8 l C/cm2, and the largest remnant magnetization of Mr*0.06 lB/f.u. with a Curie temperature about 764 K, while the Bi9Fe4.7Ni0.3Ti3O27 sample has the largest spontaneous magnetization(0.26 lB/f.u.). The improved ferromagnetic properties ofboth Bi9Fe4.7Co0.3Ti3O27 and Bi9Fe4.7Ni0.3Ti3O27 can be ascribed to the spin canting of magnetic ion-based sublattices via the Dzyaloshinskii–Moriya interaction and also the magnetic ions exchanging interactions(Fe3–O–Co3or Fe3–O–Ni3).

Magnetic logic inverter from crossed structures of defect-free graphene with large unsaturated room temperature negative magnetoresistance

Introducing defects into graphene has been widely utilized to realize the negative magnetoresistanee(MR)effect in graphene.However,the reported graphene negative MR exhibits only^10%under 10 T at room temperature to date,which extremely limits the resolution of future spintronics devices.Moreover,intentional defect introduction can also cause unintentional degradation in graphene's intrinsic properties.In this paper,we report a magnetic logic inverter based on a crossed structure of defect-free graphene,resulting in a substantial gain of 4.81 mV/T while exhibiting room temperature operation.This crossed structure of graphene shows large unsaturated room temperature negative MR with an enhancement of up to 1,000%at 9 T.A transition behavior between negative and positive MR is observed in this crossed structure and the transition temperature can be tuned by a ratio of the conductivity between in-plane and out-of-plane transport.Our results open an intriguing path for future two-dimensional spintronics device applications.

First principles study on methane reforming over Ni/TiO2（110） surface in solid oxide fuel cells under dry and wet atmospheres

Understanding the carbon-tolerant mechanisms from a microscopic view is of special importance to develop proper anodes for solid oxide fuel cells.In this work,we employed density-functional theory calculations to study the CH4 reaction mechanism over a Ni/TiO2 nanostructure,which experimentally demonstrated good carbon tolerance.Six potential pathways for methane reforming reactions were studied over the Ni/TiO2(110)surface under both dry and wet atmospheres,and the main concerns were focused on the impact of TiO2 and Ni/TiO2 interface on CO/H2 formation.Our calculations suggest that the reaction between carbon and the interfacial lattice oxygen to form CO*is the dominant pathway for CH4 reforming under both dry and wet atmospheres,and intervention of steam directly to oxidize C*with its dissociated OH*group is less favorable in energy than that to wipe off oxygen vacancy to get ready for next C*oxidation.In all investigated paths,desorption of CO*is one of the most difficult steps.Fortunately,CO*desorption can be greatly promoted by the large heat released from the previous CO*formation process under wet atmosphere.H2O adsorption and dissociation over the TiO2 surface are found to be much easier than those over Ni,yttria stabilized zirconia(YSZ)and CeO2,which should be the key reason for the greatly depressed carbon deposition over Ni-TiO2 particles than traditional YSZ-Ni and CeO2-Ni anode.Our study presents the detailed CO*formation mechanism in CH4 reforming process over the Ni/TiO2 surface,which will benefit future research for exploring new carbon-tolerant solid oxide fuel cell anodes.

A new high-temperature perovskite-like magnetic insulator

Driven by the demands of fast-developed quantum-spintronic devices and magnetic tunneling junctions,exploring excellent magnetic insulators,which can func-tion above room temperature and have high symmetry(generally speaking perovskite or perovskite-like struc-ture)to facilitate their integration potential with common single crystal oxide films or substrates as further devices,have drawn special attentions[1-4].Unfortunately.

Planar-symmetry-breaking induced antisymmetric magnetoresistance in van der Waals ferromagnet Fe_(3)GeTe_(2)

Recently discovered magnetic van der Waals(vdW)materials provide an ideal platform to explore low-dimensional magnetism and spin transport.Its vdW interaction nature opens up unprecedented opportunities to build vertically stacked heterostructures with novel properties and functionalities.By engineering the planar structure as an alternative degree of freedom,herein we demonstrate an antisymmetric magnetoresistance(MR)in a vdW Fe_(3)GeTe_(2)flake with a step terrace that breaks the planar symmetry.This antisymmetric MR originates from a sign change of the anomalous Hall effect and the continuity of the current transport near the boundary of magnetic domains at the step edge.A repeatable domain wall due to the unsynchronized magnetization switching is responsible for this sign change.Such interpretation is supported by the observation of field-dependent domain switching,and the step thickness,temperature,and magnetic field orientation dependent MR.This work opens up new opportunities to encode magnetic information by controlling the planar domain structures in vdW magnets.