Efficient nitrate electroreduction to ammonia via synergistic cascade catalysis at Cu/Fe_(2)O_(3)hetero-interfaces  

Cu/Fe_(2)O_(3)异质界面协同级联催化硝酸盐高效电还原为氨

作　　者：Xiang Zhang Weihang Li Jin Zhang Haoshen Zhou Miao Zhong 张翔;李苇杭;张进;周豪慎;钟苗(南京大学现代工程与应用科学学院,先进微结构协同创新中心,固体微结构国家实验室,地球关键材料循环前沿科学中心,江苏南京210023)

机构地区：[1]Collaborative Innovation Centre of Advanced Microstructures,National Laboratory of Solid State Microstructures,Frontiers Science Center for Critical Earth Material Cycling,College of Engineering and Applied Sciences,Nanjing University,Nanjing 210023,Jiangsu,China

出　　处：《Chinese Journal of Catalysis》2025年第1期404-413,共10页催化学报(英文)

基　　金：国家自然科学基金(22272078,22409087);催化基础国家重点实验室开放基金(2024SKL-A-016);江苏省“双创人才”计划。

摘　　要：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.氨(NH_(3))是一种重要的化学品,广泛用于合成化肥、药品、纺织品和其他行业.传统Haber-Bosch工艺用于NH合成,该工艺需高温高压条件.另一方面,工业废水中的过量硝酸盐(NO_(3))会导致水体污染.通过电催化手段,可以高效率、高选择性的将NO_(3)^(-)还原为NH_(3),不仅能够处理环境问题,还提供了一种绿色可持续的NH合成途径然而,NO_(3)^(-)还原(NO_(3)^(-)RR)过程复杂,涉及8电子和9质子的转移,并可能伴随强烈的析氢竞争反应(HER).单一金属催化剂难以在低电位下同时具备对NO_(3)^(-)和亚硝酸根(NO_(2))的高效吸附和还原能力.针对该问题,本文设计了Cu-Fe_(2)O_(3)异质结构催化剂,利用其界面上的双位点有效分步催化实现NO_(3)^(-)到NO_(2)^(-)和NO_(2)^(-)到NH_(3)的电还原过程.扫描电镜、透射电镜、X-射线衍射和X-射线光电子能谱等表征手段证实了Cu和Fe_(2)O_(3)在泡沫镍基底上的致密生长,并确定了其价态和体相组成。在0.1 mol L^(-1)KNO_(3)和1mol L^(-1)KOH_(3)的电解液中,Cu-Fe_(2)O_(3)在-0.27 V_(RHE)下展示了接近100%的NH_(3)法拉第效率,并在-0.35V_(RHE)下实现了2.71 mmol h^(-1)cm^(-2)的高NH,产率,远超单独使用Cu或Fe_(2)0_(3)催化剂的性能.同时,-0.27V_(RHE)下的半池能量效率超过35%,且在宽NO_(3)^(-)浓度范围内(0.05-1 mol L^(-1)),NH_(3)选择性均保持在90%以上.通过15N同位素标记确定了氮源完全来自KNO_(3).计时电流测试表明,反应3h后,NO_(3)^(-)的去除率高达98%.线性扫描伏安法测试(LSV)结果表明,Cu催化剂相较于Fe_(2)O_(3)具有更正的NO_(3)^(-)还原到NO_(2)^(-)起始电位(0.39V_(RHE)),并在-0.2到-0.3V_(RHE)区间里出现NO_(2)^(-)积累的电流平台.由此可见,Cu对NO,的吸附和转化为NO2的能力相较于Fe,O,更为优异.然而由于Cu对^(*)N的吸附能力较弱,导致NO2更容易脱附并在表面积累.相比之下,Fe_(2)O_(3)在NO_(2)^(-)溶液中的起始电位(>0.3V_(RHE))远高于在NO_(3)^(-)�

关 键 词：ELECTROCATALYSIS Reaction onset potential Nitrate reduction to ammonia Cascadecatalysis Heterogeneous interface 

分 类 号：O64[理学—物理化学]