理论指导构建Cu-O-Ti-O_(v)活性位点及其高效电催化还原硝酸根研究  

Theory-guided construction of Cu-O-Ti-O_(v) active sites on Cu/TiO_(2) catalysts for efficient electrocatalytic nitrate reduction

作　　者：聂翼飞 颜红萍 鹿苏微 张宏伟 齐婷婷 梁诗景 江莉龙[1,2] Yifei Nie;Hongping Yan;Suwei Lu;Hongwei Zhang;Tingting Qi;Shijing Liang;Lilong Jiang(National Engineering Research Center of Chemical Fertilizer Catalyst Fuzhou University,Fuzhou 350002,Fujian,China;Qingyuan Innovation Laboratory,Quanzhou 362801,Fujian,China)

机构地区：[1]福州大学化肥催化剂国家工程研究中心,福建福州350002 [2]清源创新实验室,福建泉州362801

出　　处：《Chinese Journal of Catalysis》2024年第4期293-302,共10页催化学报（英文）

基　　金：国家自然科学基金(22221005);国家自然科学基金(22378060);国家重点研发计划(2021YFB3801600)。

摘　　要：面向国家绿色低碳战略目标,变革化石资源合成氨技术路线变得尤为迫切,开发可再生能源制“绿氨”将成为合成氨领域未来的重要发展方向.将工业废水中的硝酸根(NO_(3)-)电催化还原为氨(NO_(3)RR),既可有效回收氨,又能消除硝酸根污染影响.然而,NO_(3)RR涉及缓慢的八电子转移过程,含有多种反应中间体,其反应机理复杂不明.此外,水系电解液中存在的析氢竞争反应也为高效NO_(3)RR催化剂的开发设计带来了巨大的挑战.为突破高效催化剂的发展瓶颈,本文通过理论模拟,在低成本的催化剂上设计了高效的NO_(3)RR催化活性位点,并利用简单的制备策略合成了目标催化剂.同时,结合原位表征技术,阐明了NO_(3)RR的反应路径及催化机理.本文通过密度泛函理论(DFT)计算发现,Cu/TiO_(2)催化剂上的Cu-O-Ti-O_(v)结构具有较好的NO_(3)-还原活性,该结构不仅能够促进反应中间体NOx-的吸附和活化,还能有效抑制竞争析氢反应,从而降低NO_(3)RR的反应能垒.在该结构上,NO_(3)RR的反应路径为:NO_(3)^(*)→NO_(2)^(*)→HONO^(*)→NO^(*)→*NOH→*N→^(*)NH→*NH2→*NH_(3)→NH_(3).基于理论计算结果,分别采用浸渍法和尿素水解法制备了系列富含Cu-O-Ti-O_(v)结构的Cu/TiO_(2)催化剂.氮气等温吸附-脱附曲线、拉曼光谱(Raman)、电子顺磁共振波谱、X射线光电子能谱(XPS)和傅立叶红外光谱等结果发现,相比于采用浸渍法制备的系列Cu/TiO_(2)催化剂,采用尿素水解法制备的Cu/TiO_(2)(CT-U)催化剂具有更大的比表面积以及更多的Cu-O-Ti-O_(v)位点,说明尿素水解法可提高Cu颗粒在TiO_(2)载体表面的分散度,增强Cu颗粒与TiO_(2)载体之间的相互作用,提高Cu/TiO_(2)催化剂表面的Cu-O-Ti-O_(v)位点含量.将以上制备出的催化剂应用于催化NO_(3)RR中,结果表明,在-1.0 V vs.RHE还原电位下,CT-U催化剂上氨产率可达3046.5μg h^(-1) mgcat^(-1),高于大多数文献报道结果.循�Electrocatalytic nitrate reduction reaction(NO_(3)RR)has been capturing immense interest in the industrial application of ammonia synthesis,and it involves complex reaction routes accompanied by multi-electron transfer,thus causing a challenge to achieve high efficiency for catalysts.Herein,we customized the Cu-O-Ti-O_(v)(oxygen vacancy)structure on the Cu/TiO_(2) catalyst,identified through density functional theory(DFT)calculations as the synergic active site for NO_(3)RR.It is found that Cu-O-Ti-O_(v) site facilitates the adsorption/association of NO_(x)-and promotes the hydrogenation of NO_(3)-to NH_(3) via adsorbed^(*)H species.This effectively suppresses the competing hydrogen evolution reaction(HER)and exhibits a lower reaction energy barrier for NO_(3)RR,with the reaction pathways:NO_(3)^(*)→NO_(2)^(*)→HONO^(*)→NO^(*)→^(*)NOH→^(*)N→^(*)NH→^(*)NH2→^(*)NH_(3)→NH_(3).The optimized Cu/TiO_(2) catalyst with rich Cu-O-Ti-O_(v) sites achieves an NH_(3) yield rate of 3046.5μg h-1 mgcat-1 at-1.0 V vs.RHE,outperforming most of the reported activities.Furthermore,the construction of Cu-O-Ti-O_(v) sites significantly mitigates the leaching of Cu species,enhancing the stability of the Cu/TiO_(2) catalyst.Additionally,a mechanistic study,using in situ characterizations and various comparative experiments,further confirms the strong synergy between Cu,Ti,and O_(v) sites,which is consistent with previous DFT calculations.This study provides a new strategy for designing efficient and stable electrocatalysts in the field of ammonia synthesis.

关 键 词：电催化硝酸盐还原 合成氨 Cu-O-Ti-O_(v)位点 协同催化 Cu/TiO_(2)催化剂 

分 类 号：TQ113.2[化学工程—无机化工] TQ426