Fe-N-C catalysts are promising substitutes for precious-metal platinum in acidic oxygen reduction reactions(ORR),yet their moderate intrinsic activity and susceptibility to reactive oxygen species(ROS)-induced degrada...Fe-N-C catalysts are promising substitutes for precious-metal platinum in acidic oxygen reduction reactions(ORR),yet their moderate intrinsic activity and susceptibility to reactive oxygen species(ROS)-induced degradation hinder practical implementation.Herein,we fabricate a Ru-Fe dual-site catalyst(RuFe-N-C)through a two-step pyrolysis strategy.Structural characterization reveals atomic-scale proximity between Ru single atoms and Fe-N_(4) moieties,exhibiting a projected distance of~1.7Å.This configuration induces Fe–N bond elongation accompanied by 2.5%lattice distortion.The optimized RuFe-N-C catalyst exhibits high ORR performance,with a half-wave potential(E_(1/2))of 0.840 V and peak power density(P_(max))of 938 mW cm^(-2) under 150 kPa absolute H_(2)-O_(2).These metrics signify substantial enhancements relative to conventional Fe-N-C benchmarks(+21 mV in E_(1/2) and+42%in P_(max)).Moreover,the catalyst maintains outstanding stability,showing merely 17 mV E_(1/2) decay after 10000 accelerated durability test(ADT)cycles.Experimental analyses reveal a bifunctional mechanism:(1)Adjacent Ru sites substantially enhance the intrinsic ORR activity of Fe-N_(4) moieties,delivering a notable turnover frequency(TOF=17.86 e site^(-1) s^(-1) at 0.85 V vs.RHE)that exceeds state-of-the-art Fe-N-C benchmarks by 1-2 orders of magnitude(<1 e site^(-1) s^(-1));(2)Ru centers function as electron relays that facilitate ROS scavenging,thus suppressing degradation.This work establishes a paradigm for engineering bimetallic single-atom catalysts through synergistic electronic modulation to concurrently enhance activity and stability.展开更多
For an optimal design of a surface-mounted permanent magnet synchronous motor(SPMSM),many objective functions should be considered.The classical optimization methods,which have been habitually designed based on magnet...For an optimal design of a surface-mounted permanent magnet synchronous motor(SPMSM),many objective functions should be considered.The classical optimization methods,which have been habitually designed based on magnetic circuit law or finite element analysis(FEA),have inaccuracy or calculation time problems when solving the multi-objective problems.To address these problems,the multi-independent-population genetic algorithm(MGA)combined with subdomain(SD)model are proposed to improve the performance of SPMSM such as magnetic field distribution,cost and efficiency.In order to analyze the flux density harmonics accurately,the accurate SD model is first established.Then,the MGA with time-saving SD model are employed to search for solutions which belong to the Pareto optimal set.Finally,for the purpose of validation,the electromagnetic performance of the new design motor are investigated by FEA,comparing with the initial design and conventional GA optimal design to demonstrate the advantage of MGA optimization method.展开更多
文摘Fe-N-C catalysts are promising substitutes for precious-metal platinum in acidic oxygen reduction reactions(ORR),yet their moderate intrinsic activity and susceptibility to reactive oxygen species(ROS)-induced degradation hinder practical implementation.Herein,we fabricate a Ru-Fe dual-site catalyst(RuFe-N-C)through a two-step pyrolysis strategy.Structural characterization reveals atomic-scale proximity between Ru single atoms and Fe-N_(4) moieties,exhibiting a projected distance of~1.7Å.This configuration induces Fe–N bond elongation accompanied by 2.5%lattice distortion.The optimized RuFe-N-C catalyst exhibits high ORR performance,with a half-wave potential(E_(1/2))of 0.840 V and peak power density(P_(max))of 938 mW cm^(-2) under 150 kPa absolute H_(2)-O_(2).These metrics signify substantial enhancements relative to conventional Fe-N-C benchmarks(+21 mV in E_(1/2) and+42%in P_(max)).Moreover,the catalyst maintains outstanding stability,showing merely 17 mV E_(1/2) decay after 10000 accelerated durability test(ADT)cycles.Experimental analyses reveal a bifunctional mechanism:(1)Adjacent Ru sites substantially enhance the intrinsic ORR activity of Fe-N_(4) moieties,delivering a notable turnover frequency(TOF=17.86 e site^(-1) s^(-1) at 0.85 V vs.RHE)that exceeds state-of-the-art Fe-N-C benchmarks by 1-2 orders of magnitude(<1 e site^(-1) s^(-1));(2)Ru centers function as electron relays that facilitate ROS scavenging,thus suppressing degradation.This work establishes a paradigm for engineering bimetallic single-atom catalysts through synergistic electronic modulation to concurrently enhance activity and stability.
基金This work was supported in part by the National Natural Science Foundation of China under Grant51507016。
文摘For an optimal design of a surface-mounted permanent magnet synchronous motor(SPMSM),many objective functions should be considered.The classical optimization methods,which have been habitually designed based on magnetic circuit law or finite element analysis(FEA),have inaccuracy or calculation time problems when solving the multi-objective problems.To address these problems,the multi-independent-population genetic algorithm(MGA)combined with subdomain(SD)model are proposed to improve the performance of SPMSM such as magnetic field distribution,cost and efficiency.In order to analyze the flux density harmonics accurately,the accurate SD model is first established.Then,the MGA with time-saving SD model are employed to search for solutions which belong to the Pareto optimal set.Finally,for the purpose of validation,the electromagnetic performance of the new design motor are investigated by FEA,comparing with the initial design and conventional GA optimal design to demonstrate the advantage of MGA optimization method.
