Electrochemical nitrate(NO_(3)^(-))reduction offers a promising route for ammonia(NH_(3))synthesis from industrial wastewater using renewable energy.However,achieving selective and active NO_(3)^(-)to NH_(3)conversion...Electrochemical nitrate(NO_(3)^(-))reduction offers a promising route for ammonia(NH_(3))synthesis from industrial wastewater using renewable energy.However,achieving selective and active NO_(3)^(-)to NH_(3)conversion at low potentials remains challenging due to complex multi-electron transfer processes and competing reactions.Herein,we tackle this challenge by developing a cascade catalysis approach using synergistic active sites at Cu-Fe_(2)O_(3)interfaces,significantly reducing the NO_(3)^(-)to NH_(3)at a low onset potential to about+0.4 V_(RHE).Specifically,Cu optimizes^(*)NO_(3)adsorption,facilitating NO_(3)^(-)to nitrite(NO_(2)-)conversion,while adjacent Fe species in Fe_(2)O_(3)promote the subsequent NO_(2)-reduction to NH_(3)with favorable^(*)NO_(2)adsorption.Electrochemical operating experiments,in situ Raman spectroscopy,and in situ infrared spectroscopy consolidate this improved onset potential and reduction kinetics via cascade catalysis.An NH_(3)partial current density of~423 mA cm^(-2)and an NH_(3)Faradaic efficiency(FENH_(3))of 99.4%were achieved at-0.6 V_(RHE),with a maximum NH_(3)production rate of 2.71 mmol h^(-1)cm^(-2)at-0.8 V_(RHE).Remarkably,the half-cell energy efficiency exceeded 35%at-0.27 V_(RHE)(80%iR corrected),maintaining an FENH_(3)above 90%across a wide range of NO_(3)^(-)concentrations(0.05^(-1)mol L^(-1)).Using 15N isotopic tracing,we confirmed NO_(3)^(-)as the sole nitrogen source and attained a 98%NO_(3)^(-)removal efficiency.The catalyst exhibit stability over 106-h of continuous operation without noticeable degradation.This work highlights distinctive active sites in Cu-Fe_(2)O_(3)for promoting the cascade NO_(3)^(-)to NO_(2)^(-)and NO_(2)^(-)to NH_(3)electrolysis at industrial relevant current densities.展开更多
文摘Electrochemical nitrate(NO_(3)^(-))reduction offers a promising route for ammonia(NH_(3))synthesis from industrial wastewater using renewable energy.However,achieving selective and active NO_(3)^(-)to NH_(3)conversion at low potentials remains challenging due to complex multi-electron transfer processes and competing reactions.Herein,we tackle this challenge by developing a cascade catalysis approach using synergistic active sites at Cu-Fe_(2)O_(3)interfaces,significantly reducing the NO_(3)^(-)to NH_(3)at a low onset potential to about+0.4 V_(RHE).Specifically,Cu optimizes^(*)NO_(3)adsorption,facilitating NO_(3)^(-)to nitrite(NO_(2)-)conversion,while adjacent Fe species in Fe_(2)O_(3)promote the subsequent NO_(2)-reduction to NH_(3)with favorable^(*)NO_(2)adsorption.Electrochemical operating experiments,in situ Raman spectroscopy,and in situ infrared spectroscopy consolidate this improved onset potential and reduction kinetics via cascade catalysis.An NH_(3)partial current density of~423 mA cm^(-2)and an NH_(3)Faradaic efficiency(FENH_(3))of 99.4%were achieved at-0.6 V_(RHE),with a maximum NH_(3)production rate of 2.71 mmol h^(-1)cm^(-2)at-0.8 V_(RHE).Remarkably,the half-cell energy efficiency exceeded 35%at-0.27 V_(RHE)(80%iR corrected),maintaining an FENH_(3)above 90%across a wide range of NO_(3)^(-)concentrations(0.05^(-1)mol L^(-1)).Using 15N isotopic tracing,we confirmed NO_(3)^(-)as the sole nitrogen source and attained a 98%NO_(3)^(-)removal efficiency.The catalyst exhibit stability over 106-h of continuous operation without noticeable degradation.This work highlights distinctive active sites in Cu-Fe_(2)O_(3)for promoting the cascade NO_(3)^(-)to NO_(2)^(-)and NO_(2)^(-)to NH_(3)electrolysis at industrial relevant current densities.
