查看更多>>摘要：Designing bifunctional oxygen reduction/evo-lution(ORR/OER)catalysts with high activity,robust stability and low cost is the key to accelerating the com-mercialization of rechargeable zinc-air battery(RZAB).Here,we propose a template-assisted electrospinning strategy to in situ fabricate 3D fibers consisting of FeNi nanoparticles embedded into N-doped hollow porous car-bon nanospheres(FeNi@NHCFs)as the stable binder-free integrated air cathode in RZAB.3D interconnected con-ductive fiber networks provide fast electron transfer path-ways and strengthen the mechanical flexibility.Meanwhile,N-doped hollow porous carbon nanospheres not only evenly confine FeNi nanoparticles to provide sufficient catalytic active sites,but also endow optimum mass transfer environment to reduce diffusion barrier.The RZABs assembled by FeNi@NHCFs as integrated air cathodes exhibit outstanding battery performance with high open-circuit voltage,large discharge specific capacity and power density,durable cyclic stability and great flexibility.Thus,this work brings a useful strategy to fabricate the integrated electrodes without using any polymeric binders for metal air batteries and other related fields.
查看更多>>摘要：The severe volumetric expansion and poor con-ductivity of silicon when used as anode in lithium-ion bat-teries present challenges in maintaining the stability of electrochemical performance.Herein,the binding between silicon nanoparticles and carbon nanotubes(CNTs)is achieved by the utilization of sodium alginate(SA),which is then strengthened by the coordination between Ca2+and the carboxyl group(-COO-)of SA,resulting in a stable con-ductive network with ionic transport pathway.The consoli-dated binding relationship enables silicon-based anode material to possess high mechanical strength and strong deformation resistance,preventing the separation of silicon from CNTs network.Consequently,this silicon-based anode material demonstrates a discharge specific capacity of 811 mAh·g-1 after 100 cycles at a current density of 1 A·g-1,and exhibits high rate performance,with a discharge specific capacity of 1612 mAh·g-1 at 2 A·g-1.
查看更多>>摘要：Cost-efficient and high-performance cathodes play a crucial role in the advancement of grid-scale sodium-ion batteries(SIBs).As promising high-capacity cathode materials for SIBs,O3-type Na-based layered transition metal oxides constantly experience inadequate air stability and complex phase transitions.Herein,a comprehensive investigation was conducted to explore the impact of Ca substitution on both the electrochemical performance and structural stability of O3-Na1-2x CaxNi0.25Fe0.5Mn0.25O2(x=0,0.02 and 0.05)that is pro-posed.With proper Ca content,O3-type Na0.96Ca0.02-Ni0.25Fe0.5Mn0.25O2 can deliver a reversible capacity of 122.1 mAh·g-1 at 10 mA·g-1,with capacity retention of 83.4％after 200 cycles at 50 mA·g-1 and good rate capability.Its air sensitivity is investigated,and its poten-tial as the Na host in full cells has been studied.In situ X-ray diffraction reveals the facilitated O3-P3-O3 phase transitions of such cathode during the whole electrochem-ical reaction.Such a simple and effective strategy may reveal a new avenue for high-stable O3-type cathodes and promote the practical applications of SIBs.
Yang WangZhi-Yang WanJia-Jin KuangMing-Tai Wang...
5712-5719页
查看更多>>摘要：The planar heterojunction solar cells based on the GaAs films doped with gold nanoparticles(Au NPs)are investigated by a finite-difference time-domain method.The numerical results show that Au NPs effectively increase the light absorption and short-circuit current(Jsc)of GaAs solar cells,when saving GaAs consumption by reducing film thickness.For the GaAs film of 200 nm in thickness,the presence of Au NPs boosts the device Jsc up to 36.94 mA.cm-2,1.29 times that of the counterpart device without Au NPs.In addition,one requires the pure GaAs film of 500-600 nm in thickness in order to get the absorption and Jsc comparable to those from the 200-nm-thick GaAs film doped with Au NPs.It is revealed that the improved Jsc upon doping with Au NPs predominantly originates from the increased absorption of GaAs film as the result of the plasmon resonance effect of Au NPs excited by incident photons.Our results demonstrate that doping photon-harvesting layer with Au NPs is an effective strategy to prepare the solar cells with a strong spectral response and a reduced material consumption.
查看更多>>摘要：Eco-friendly lead-free tin(Sn)-based per-ovskites have drawn much attention in the field of photo-voltaics,and the highest power conversion efficiency(PCE)of Sn-based perovskite solar cells(PSCs)has been recently approaching 15％.However,the PCE improve-ment of Sn-based PSCs has reached bottleneck,and an unambiguous guidance beyond traditional trial-and-error process is highly desired for further boosting their PCE.In this work,machine learning(ML)approach based on artificial neural network(ANN)algorithm is adopted to guide the development of Sn-based PSCs by learning from currently available data.Two models are designed to pre-dict the bandgap of newly designed Sn-based perovskites and photovoltaic performance trends of the PSCs,and the practicability of the models are verified by real experi-mental data.Moreover,by analyzing the physical mecha-nisms behind the predicted trends,the typical characteristics of Sn-based perovskites can be derived even no relevant inputs are provided,demonstrating the robustness of the developed models.Based on the models,it is predicted that wide bandgap Sn-based PSCs with optimized interfacial energy level alignment could obtain promising PCE breaking 20％.At last,critical suggestions for future development of Sn-based PSCs are provided.This work opens a new avenue for guiding and promoting the development of high-performing Sn-based PSCs.
查看更多>>摘要：The aqueous ammonium ion(NH4+)is a promising charge carrier in virtue of its safety,environ-mental friendliness,abundant resources and small hydrated ionic size.The exploration of NH4+host electrodes with good reversibility and large storage capacity to construct high-performance ammonium-ion hybrid capacitors(AIHCs),however,is still in its infancy.Herein,a facile etching technique is put forward to produce oxygen-defi-cient MnO2(Od-MnO2)as the electrode material for NH4+storage.According to the experimental and theoretical calculation results,the etching process not only creates more porosity,offering abundant active sites,but also generates abundant oxygen vacancies,which modify the structure of pristine MnO2,enhance charge storage capacity and boost ion diffusion kinetics.Consequently,Od-MnO2 can deliver a specific capacity of 155 mAh.g-1 at 0.5 A·g-1 and a good long-term cycling stability with 86.8％capacity maintained after 10,000 cycles at 5.0 A·g-1.Additionally,the NH4+storage mechanism was evidenced by several ex-situ characterization analyses.To examine the actual implementation of Od-MnO2 as a pos-itive electrode for NH4+full device,AIHCs are assembled with activated carbon functionalized with Fe3O4 nanopar-ticles(Fe3O4@AC)as a negative electrode.A high specific capacitance of 184 F·g-1 at 0.5 A·g-1,satisfactory energy density of 102 Wh·kg-1 at 500 W·kg-1,a low self-dis-charge rate and good cycling durability after 10,000 cycles are attained.The electrochemical performance of these AIHCs is comparable to or surpass those of traditional supercapacitors with metal ions as charge carriers,high-lighting the advantages of structural modification in enhancing the NH4+storage performance.
查看更多>>摘要：Electrocatalytic CO2 reduction reaction(CO2RR)to produce multicarbon(C2+)products over Cu-based catalysts represents an ideal approach for renewable energy storage and carbon emissions reduction.The Cu0/Cuδ+interfaces are widely recognized as crucial sites that promote C-C coupling and enhance the generation of C2+products.However,a major challenge arises from the tendency of Cuδ+active sites within Cu0/Cuδ+interfaces to undergo reduction to Cu0 during the CO2RR process,leading to a decline in catalytic performance.Hence,it is crucial to establish durable Cu0/Cuδ+interfaces to enhance the conversion of CO2 to C2+products.In this work,an iodine modification strategy is proposed to prepare a stable Cu@CuI composite catalyst with well-maintained Cu0/Cuδ+interfaces through a one-step redox reaction between iodine and copper.The optimized Cu@CuI-3 composite catalyst demonstrates an excellent performance in CO2RR,achieving a Faradaic efficiency of 75.7％for C2+products and a partial current density of 288 mA·cm-2 at-1.57 VRHE in a flow cell.Operando techniques reveal that a numerous persistent Cuδ+species exist on the surface of the Cu@CuI-X composite catalyst even after CO2RR due to the presence of adsorbed iodine ions,which prevent complete reduction of Cuδ+species to Cu0 owing to their high electronegativity.Density functional theory calculations further verify that adsorbed iodine ions on the surface of Cu@CuI-X serve as charge regulators by adjusting local charge density,thereby facilitating the formation of*CHO intermediates from CO2 and lowering the energy barriers associated with coupling the*CHO and*CO intermediates during CO2RR.Consequently,this phenomenon enhances the selectivity toward C2+products during electrocatalytic CO2 reduction.
查看更多>>摘要：Designing rational transition-metal/carbon composites with highly dispersed and firmly anchored nanoparticles(NPs)to prevent agglomeration and shedding is crucial for realizing excellent electrocatalytic perfor-mances.Herein,a biomass pore-confined strategy based on mesoporous willow catkin is explored to obtain uniformly dispersed CoFe NPs in N-doped carbon nanotubes and hollow carbon fibers(CoFe@N-CNTs/HCFs).The resul-tant catalyst exhibits enhanced electrocatalytic perfor-mance,which affords a half-wave potential of 0.86 V(vs.RHE)with a limited current density of 6.0 mA-cm-2 for oxygen reduction reaction and potential of 1.67 V(vs.RHE)at 10 mA·cm-2 in 0.1 M KOH for oxygen evolution reaction.When applied to rechargeable zinc-air batteries,a maximum power density of 340 mW·cm-2 and long-term cyclic durability over 800 h are achieved.Such superior bifunctional electrocatalytic activities are ascribed to the biocarbon matrix with abundant mesopores and unob-structed hollow channels,CoFe NPs with high dispersion and controllable nanoscale and the hybrid composite with optimized electronic structure.This work presents an effective approach for constraining the size and dispersion of NPs in a low-cost biocarbon substrate,offering valuable insights for designing advanced oxygen electrocatalysts.
查看更多>>摘要：High-performance bifunctional oxygen electro-catalysts that simultaneously boost the sluggish oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)need to be developed for advanced rechargeable Zn-air battery applications.In this work,a zeolitic imidazolate framework(ZIF)-phase conversion associated with a sub-sequent thermal fixing strategy was developed to fabri-cate bimetallic CoFe single atoms/clusters embedded in N-doped carbon(denoted as CoFe-N-C)nanorods,which can serve as efficient bifunctional ORR/OER electrocata-lysts.Microstructural observation and X-ray absorption spectroscopy analysis confirm the co-existence of highly active Co/Fe-Nx dual sites and CoFe alloy nanoclusters.X-ray photoelectron spectroscopy(XPS)results prove that implanting secondary Fe atoms into Co-N-C matrix nanorods can induce electronic redistribution of atomic Co/Fe active sites and generate synergistic effects,which would optimize the adsorption energy of the reaction intermediates and thus enhance the bifunctional ORR/OER activity.The bimetallic CoFe-N-C nanorods exhibit sig-nificantly enhanced bifunctional ORR/OER activity and stability than the monometallic Co/Fe-N-C nanorods in alkaline electrolytes in terms of a very positive half-wave potential of 0.90 V(vs.reversible hydrogen electrode(RHE))for ORR,and an overpotential of 440 mV to reach current density of 10 mA·cm-2 for OER,yielding a small overpotential gap of 0.77 V.Furthermore,the rechargeable Zn-air batteries using bimetallic CoFe-N-C nanorods as air-cathode catalyst demonstrates peak power density of 200.7 mW·cm-2 and robust cycling stability of up to 200 h,corresponding to 1200 discharge-charge cycles.
查看更多>>摘要：Single-atom catalysts(SACs)have been widely utilized in electrochemical nitrogen reduction reactions(NRR)due to their high atomic utilization and selectivity.Owing to the unique sp/sp2 co-hybridization,graphyne materials can offer stable adsorption sites for single metal atoms.To investigate the influence of the sp/sp2 hybrid carbon ratio on the electrocatalytic NRR performance of graphyne,a high-throughput screening of 81 catalysts,with 27 transition metals loaded on graphyne(GY1),graphdiyne(GY2),and graphtriyne(GY3),was conducted using first-principles calculations.The results of the screening revealed that Ti@GY3 exhibits the lowest energy barrier for the rate-determining step(0.32 eV)in NRR.Further,to explore the impact of different sp/sp2-hybridized carbon ratios on the catalytic activity of SACs,the mechanism of nitrogen(N2)adsorption,activation,and the comprehen-sive pathway of NRR on Ti@GY1,Ti@GY2,and Ti@GY3 was systematically investigated.It was found that the ratio of sp/sp2-hybridized carbon can significantly modulate the d-band center of the metal,thus affecting the energy barrier of the rate-determining step in NRR,decreasing from Ti@GY1(0.59 eV)to Ti@GY2(0.49 eV),and further to Ti@GY3(0.32 eV).Additionally,the Hall conductance was found to increase with the bias voltage in the range of 0.4-1 V,as calculated by Nanodcal software,demonstrating an improvement in the conduc-tivity of the SAC.In summary,this work provides theo-retical guidance for modulating the electrocatalytic nitrogen reduction activity of SACs by varying the ratio of sp/sp2 hybrid carbon,with Ti@GY3 showing potential as an excellent NRR catalyst.
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维普