Enhancing the activity of FeNi bimetallic electrocatalysts on overall water splitting by Nd_(2)O_(3)-induced FeNi lattice contraction

The development of high-efficiency and cost-effective bifunctional electrocatalysts for overall water splitting remains a formidable challenge.Herein,FeNi-Nd_(2)O_(3) nanoparticles anchored on N-doped carbon nanotubes(FeNi-Nd_(2)O_(3)/NCN) are designed for highly effective overall water splitting via a facile two-step hydrothermal approach.The synthetic FeNi-Nd_(2)O_(3) hetero-trimers(Fe 2p-Ni 2p-Nd 3d orbital coupling)on NCN achieve excellent oxygen evolution reaction(OER) and hydrogen evolution reaction(HER) activities with overpotentials of 270 and 120 mV at 10 mA cm^(-2) in 1 M KOH solution.Moreover,a small voltage of 1.52 V at 10 mA cm^(-2) is achieved when FeNi-Nd_(2)O_(3)/NCN is assessed as bifunctional catalyst for overall water splitting,which is superior to the typically integrated Pt/C and RuO_(2) counterparts(1.54 V at 10 mA cm^(-2)).The related characterizations including X-ray absorption fine structure(XAFS)spectroscopy show that the remarkably improved activity is originated from Nd_(2)O_(3)-induced FeNi bimetallic lattice contraction.Furthermore,density functional theory(DFT) calculations indicate that the lattice contraction reduces binding energies of intermediates by downshifting the position of FeNi bimetallic d-band center relative to the Fermi level to optimize catalytic performance.Therefore,the Nd_(2)O_(3)-induced FeNi bimetallic lattice contraction may provide a new perspective for designing and synthesizing innovative catalytic systems.

Nucleation of Boron-Nitrogen on Transition Metal Surface:A First-Principles Investigation

Boron nitrogen(BN)monolayer has attracted considerable attention because of their suc-cessful incorporation with graphene based nanodevices.However,many important aspects of the growth mechanisms are still not well explored.Using density functional theory(DFT)calculations,we found that Cu(111)surface is more suitable to be used as a substrate to grow BN monolayer compared with Ni(111)surface.Moreover,we explored that one-dimensional(1D)BN chain configuration is dominant to the two-dimensional(2D)BN ring formation from one pair to five BN pairs deposited on Cu(111)surface.Energetically stable structure transformation of BN monolayer from 1D BN chain to 2D BN ring occurs when the number of pairs is n>5.It is suggested that,as the number of BN pairs increases the energetically stable structures achieve.

四面体超晶格中高温铁磁半导体的预测

铁磁(FM)半导体兼具半导体(如逻辑器件)和磁性材料(如记忆存储器)的优点,半个多世纪以来一直受到广泛关注.然而,铁磁半导体的发展受到候选材料稀缺以及居里温度低的阻碍.铁磁性通常在具有八面体配位的过渡金属化合物中被发现.而具有较小晶体场分裂和较弱反铁磁(AFM)直接交换的四面体配位化合物可能是高温铁磁体的潜在候选者,但很少被探索.在这项工作中,我们提出了高温铁磁半导体可以在四面体配位超晶格(SL)中实现.在第一性原理计算的基础上,我们系统地研究了一系列MX/TMX (MX表示12-16,13-15或14-14族四面体半导体,TM表示3d过渡金属,X表示配体)超晶格.其中,SiC/CrC SL是一种稳定的铁磁半导体材料,具有0.363 eV的间接带隙和~935 K的高居里温度.此外,我们还探讨了Cr原子层的分布和层间磁耦合,预测了单轴应变引起了反铁磁到铁磁的相变.这些发现为实现四面体配位超晶格的高温铁磁半导体在未来自旋电子应用中开辟了新的机会.

High-density triple-phase contact points for enhanced photocatalytic CO_(2) reduction to methanol

The efficiency of photocatalytic CO_(2) reduction reaction(PCRR)is restricted by the low solubility and mobility of CO_(2) in water,poor CO_(2) adsorption capacity of catalyst,and competition with hydrogen evolution reaction(HER).Recently,hydrophobic modification of the catalyst surface has been proposed as a potential solution to induce the formation of triple-phase contact points(TPCPs)of CO_(2)(gas phase),H_(2) O(liquid phase),and catalysts(solid phase)near the surface of the catalyst,enabling direct delivery of highly concentrated CO_(2) molecules to the active reaction sites,resulting in higher CO_(2) and lower H+surface concentrations.The TPCPs thus act as the ideal reaction points with enhanced PCRR and suppressed HER.However,the initial synthesis of triple-phase photocatalysts tends to possess a lower bulk density of TPCPs due to the simple structure leading to limited active points and CO_(2) adsorption sites.Here,based on constructing a hydrophobic hierarchical porous TiO_(2)(o-HPT)with interconnected macropores and mesopores structure,we have significantly increased the density of TPCPs in a unit volume of the photocatalyst.Compared with hydrophobic macroporous TiO_(2)(o-MacPT)or mesoporous TiO_(2)(o-MesPT),the o-HPT with increased TPCP density leads to enhanced photoactivity,enabling a high methanol production rate with 1111.5μmol g^(−1) h^(−1) from PCRR.These results emphasize the significance of high-density TPCPs design and propose a potential path for developing efficient PCRR systems.

Nitrogen doped porous carbon-based bifunctional oxygen electrocatalyst with controllable phosphorus content for zinc-air battery

The controllable construction of non-noble metal based bifunctional catalysts with high activities towards oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)is of great significance,but remains a challenge.Herein,we reported an effective method to synthesize cobalt-nitrogen doped mesoporous carbon-based bifunctional oxygen electrocatalyst with controllable phosphorus content(Co-N-P_(X)-MC,X=0.5,1.0,1.5,2.0).The mesoporous carbon substrate endowed the asprepared samples with more exposed active surface(236.50 m^(2)·g^(−1))and the most appropriate doping ratio of phosphorus had been investigated to be 1.5(Co-N-P1.5-MC).For ORR,Co-N-P1.5-MC exhibited excellent catalytic activity with more positive onset potential(1.01 V)and half-wave potential(0.84 V)than the other samples.For OER,Co-N-P1.5-MC also showed a low overpotential of 415 mV.Combining experimental results and density-functional theory(DFT)calculations,the outstanding bifunctional catalytic performance of Co-N-P1.5-MC was due to the synergistic cooperation between the P and N dopants,which could reduce the reaction barriers and was favorable for ORR and OER.Moreover,the Zn-air battery using Co-N-P1.5-MC as the cathode showed remarkable battery performance with high stability(could operate stably for over 160 h at 10 mA·cm^(−2))and maximum power density(119 mW·cm^(−2)),demonstrating its potential for practical applications.This work could provide significant enlightenment towards the design and construction of bifunctional oxygen electrocatalyst for next-generation electrochemical devices.

Enhanced charge separation by continuous homojunction with spatially separated redox sites for hydrogen evolution

Photocatalytic hydrogen generation represents a promising strategy for the establishment of a sustainable and environmentally friendly energy reservoir.However,the current solar-to-hydrogen conversion efficiency is not yet sufficient for practical hydrogen production,highlighting the need for further research and development.Here,we report the synthesis of a Sn-doped TiO_(2)continuous homojunction hollow sphere,achieved through controlled calcination time.The incorporation of a gradient doping profile has been demonstrated to generate a gradient in the band edge energy,facilitating carrier orientation migration.Furthermore,the hollow sphere’s outer and inner sides provide spatially separated reaction sites allowing for the separate acceptance of holes and electrons,which enables the rapid utilization of carriers after separation.As a result,the hollow sphere TiO_(2)with gradient Sn doping exhibits a significantly increased hydrogen production rate of 20.1 mmol·g^(−1)·h^(−1).This study offers a compelling and effective approach to the designing and fabricating highly efficient nanostructured photocatalysts for solar energy conversion applications.

Room-temperature vertical ferroelectricity in rhenium diselenide induced by interlayer sliding

One variety of ferroelectricity that results from lateral relative movements between the adjacent atomic layers is referred to as sliding ferroelectricity,which generates an interfacial charge transfer and hence a polarization reversal.The mechanism of sliding ferroelectricity existent in van der Waals crystals is quite distinct from the conventional ferroelectric switching mechanisms mediated by ion displacement.It creates new possibilities for the design of two-dimensional(2D)ferroelectrics since it can be achieved even in non-polar systems.Before 2D ferroelectrics can be widely employed for practical implementations,however,there is still significant work to be done on several fronts,such as exploring ferroelectricity possibly in more potential 2D systems.Here,we report the experimental observation of room-temperature robust vertical ferroelectricity in layered semiconducting rhenium diselenide(ReSe_(2)),a representative member of the transition metal dichalcogenides material family,based on a combined research of nanoscale piezoresponse and second harmonic generation measurements.While no such ferroelectric behavior was seen in 1L ReSe_(2),2L ReSe_(2)exhibits vertical ferroelectricity at ambient environment.Based on density-functional theory calculations,we deduce that the microscopic origin of ferroelectricity for ReSe_(2)is uncompensated vertical charge transfer that is dependent on in-plane translation and switchable upon interlayer sliding.Our findings have important ramifications for the ongoing development of sliding ferroelectricity since the semiconducting properties and low switching barrier of ReSe2 open up the fascinating potential for functional nanoelectronics applications.

Reconcile the contradictory wettability requirements for the reduction and oxidation half-reactions in overall CO_(2) photoreduction via alternately hydrophobic surfaces

The overall photocatalytic CO_(2) reduction reaction(OPCRR)that can directly convert CO_(2) and H_(2)O into fuels represents a promising renewable energy conversion technology.As a typical redox reaction,the OPCRR involves two half-reactions:the CO_(2) reduction half-reaction(CRHR)and the water oxidation half-reaction(WOHR).Generally,both half-reactions can be promoted by adjusting the wettability of catalysts.However,there is a contradiction in wettability requirements for the two half-reactions.Specifically,CRHR prefers a hydrophobic surface that can accumulate more CO_(2) molecules on the active sites,ensuring the appropriate ratio of gas-phase(CO_(2))to liquid-phase(H_(2)O)reactants.Conversely,the WOHR prefers a hydrophilic surface that can promote the departure of the gaseous product(O_(2))from the catalyst surface,preventing isolation between active sites and the reactant(H_(2)O).Here,we successfully reconciled the contradictory wettability requirements for the CRHR and WOHR by creating an alternately hydrophobic catalyst.This was achieved through a selectively hydrophobic modification method and a charge-transfer-control strategy.Consequently,the collaboratively promoted CRHR and WOHR led to a significantly enhanced OPCRR with a solar-to-fuel conversion efficiency of 0.186%.Notably,in ethanol production,the catalyst exhibited a 10.64-fold increase in generation rate(271.44μmol g^(-1)h~(-1))and a 4-fold increase in selectivity(55.77%)compared to the benchmark catalyst.This innovative approach holds great potential for application in universal overall reactions involving gas participation.

Nature of spin-lattice coupling in two-dimensional CrI_(3) and CrGeTe_(3)

Spin-lattice (SL) coupling plays an important role in spintronic applications given its effects on magnetic,ferroelectric,optical,and thermodynamic properties.Experiments and theoretical calculations have revealed a large SL coupling effect in CrGeTe_(3) and CrI_(3) monolayers.However,the microscopic origin of SL coupling in these systems is still unclear.In this work,we develop a systematic method to explore the atomistic mechanism of SL coupling based on the density functional theory.We find that the first-and second-order SL couplings in ternary system CrGeTe_(3) are considerably stronger than those in binary system CrI_(3).For the first-order SL coupling,the Cr ions of the magnetic pair and Ge ions positively contribute to the strain enhancement of ferromagnetism in CrGeTe_(3).However,the Cr ions provide a negative contribution in CrI_(3).Furthermore,our tight-binding analysis suggests that the p-d hopping in CrGeTe_(3) gradually decreases with the tensile strain,rapidly enhancing the ferromagnetism under the tensile strain.The large frequency shifts in CrGeTe_(3) are caused by the large second-order exchange derivatives (one type of second-order SL coupling) of the Cr ions of the magnetic pair.