摘要
随着工农业的快速发展及城市化进程的加速,含硝酸盐废水的处理问题日益突出,对生态环境与人类健康造成了严重的威胁.电催化硝酸盐还原制备氨是一种在温和条件下去除硝酸盐污染物并生成氨的可行策略,兼具环境与经济双重价值.然而,由于硝酸盐还原制氨过程涉及复杂的电子质子转移过程,在低浓度(≤100 ppm)硝酸盐条件下,硝酸盐转化率低和氨产率不足严重制约了该技术的工业应用和发展潜力.因此,开发新型的可精准调控催化中心结构的催化剂材料,并通过调控催化剂表面对含N中间体的吸附来提高硝酸盐的转化率和氨的产率,对于解决上述问题具有重要意义.本文通过过渡金属离子M^(2+)(M=Fe,Co,Ni和Cu)与1,2,4,5-苯四胺(BTA)配体配位合成了四种一维共轭配位聚合物链(1D CCPs)材料,并将其应用于电催化硝酸盐还原制备高附加值产物氨.通过改变金属离子,电催化硝酸盐还原的选择性和活性得到了提高,这些1D CCPs结构为探索电催化硝酸盐还原制氨中的结构-活性关系提供了良好的平台.反应2 h后,Cu-BTA的产氨速率达到2.28 mg h^(-1)c^(-2),该结果是已报道的低浓度硝酸盐还原产氨的较高水平,在4h内硝酸盐的转化率达到96.74%,氨的选择性为79.46%.在经过25次循环实验后,催化性能依然保持良好.密度泛函理论计算结果表明,富电子Cu中心减弱了*NO中间体π轨道向Cu的d轨道的电子转移效率,并增强了Cu d_(yz)轨道对*NO的π轨道的电子反馈作用,提升了*NO中间体的自由能,N=O键被削弱,降低了NO→*NHO的ΔG值,进一步促进了氢化反应,提高了产氨速率.此外,Cu-BTA对氨的吸附能最小,有利于活性中心表面产生的氨快速脱除,加快了吸附-催化转化-脱附循环的速率,并且降低了催化中心中毒的可能性,从而实现了高催化活性和长期稳定性.综上,由于电催化硝酸盐还原制氨过程涉及八电子九质子转移�
Electrocatalytic reduction of nitrate to ammonia(NITRR)is a promising strategy to remove nitrate pollutants and generate ammonia under mild conditions.However,the low conversion rate of nitrate and insufficient ammonia production rate severely limits the development of NITRR.Manipulating the adsorption of N-intermediates on the surface of catalyst greatly affects the activity and the selectivity of catalytic reaction.Herein,four one-dimensionalπ-d conjugated coordination polymers(1D CCPs)are synthesized and applied to NITRR.The selectivity and activity of NITRR are well improved by metal ion substitutions,which regulate the adsorption towards generated intermediates.The ammonia production rate reaches 2.28 mg h^(-1) cm^(-2) over Cu-BTA in 2 h,comparable to recent works at low nitrate concentrations,and the conversion rate of nitrate up to 96.74%in four hours with 79.46%ammonia selectivity.Density functional theory calculations reveal that Cu-BTA had electron-richer Cu center,causing the enhanced free energy of*NO and the attenuation of N=O bond.Therefore,theΔG required for converting*NO to*NHO is reduced and the further hydrogenation is promoted.Additionally,the adsorption energies toward NH3 are also effectively reduced by metal ions substitution,accelerating the desorption of generated and adsorbed NH3,making the turnover of catalysts more frequent.
作者
刘青
成雪峰
霍锦艳
刘小芳
董慧龙
曾宏波
徐庆锋
路建美
Qing Liu;Xue-Feng Cheng;Jin-Yan Huo;Xiao-Fang Liu;Huilong Dong;Hongbo Zeng;Qing-Feng Xu;Jian-Mei Lu(College of Chemistry,Chemical Engineering and Materials Science,Collaborative Innovation Center of Suzhou Nano Science and Technology,Soochow University,Suzhou 215123,Jiangsu,China;School of Materials Engineering,Changshu Institute of Technology,Changshu 215500,Jiangsu,China;Department of Chemical and Materials Engineering,University of Alberta,Edmonton,Canada)
基金
江苏省基础研究计划重点项目(BK20202012)
国家自然科学基金(21938006,51773144)
江苏省高等学校自然科学研究重点项目(20KJA610001)
江苏省高等学校优势学科建设工程资助项目(PAPD)
科技部智能纳米环保新材料与检测技术国际联合研究中心项目(SDGH2303).
关键词
硝酸盐还原
氨合成
电催化
一维共轭配位聚合物
吸附调控
Nitrate reduction
Ammonia synthesis
Electrocatalysis
One-dimensional conjugated
coordination polymers
Adsorption manipulation
