摘要
利用光催化还原技术将CO_(2)定向转化为乙醇(CO_(2)-乙醇)是解决日益严重的环境污染和能源危机的理想途径之一.然而,CO_(2)分子的高化学惰性以及C-C耦合反应的高化学能垒导致目前CO_(2)-乙醇转化反应的产率和选择性较低.因此,设计构建能够快速活化CO_(2)分子并同时促进C-C耦合的光催化材料具有重要研究意义.尽管已有研究表明,Cu+物种在促进C-C耦合方面具有一定优势,但其在催化反应过程中的不稳定性限制了其实际应用.基于上述认识,本文通过理论模拟预测发现,相比于Cu单原子,CuNi异核双原子(CuNi HDAs)不仅在CO_(2)活化及C-C耦合方面更具优势,而且能够有效锚定并固化Cu+物种.因此,本文设计了一种三步合成策略,精准地将Cu单原子锚定在(Ni,Zr)-UiO-66-NH2材料的Ni位上,合成了以CuNi HDAs为活性位点的Cu-(Ni,Zr)-UiO-66-NH2光催化材料.在可见光照射下,Cu-(Ni,Zr)-UiO-66-NH2表现出较好的催化CO_(2)-乙醇转化活性,其乙醇的产率和选择性分别达到~3218μmol·gCu^(-1)·h^(-1)和97.3%.光谱分析和密度泛函理论计算结果表明,Cu-(Ni,Zr)-UiO-66-NH2材料较好的光催化性能来源于CuNi HDAs特殊的电子结构.首先,CuNi HDAs通过CuNi-O界面化学键与吸光组分(Ni,Zr)-UiO-66-NH2相连,利用界面Cu-Ni-O键作为快速电子传输通道,CuNi HDAs能够富集到足够的光生电子用于涉及12电子的CO_(2)-乙醇转化反应,使得乙醇产率大幅提升.其次,Cu,Ni和O三种原子由于电子亲核能的差异,导致CuNi HDAs的电子分布呈现不对称性.这种不对称的电子结构能有效诱导CO_(2)分子的极化,打破其结构的对称性,从而显著降低CO_(2)分子的活化能.再次,相比于Cu单原子,CuNi HDAs对*CO中间体的吸附能力更强,这不仅增强了活性位点表面*CO中间体的覆盖度,还抑制CO的生成,为C-C耦合创造了充分条件.最后,由于Cu-Ni双活性位电子密度的差异,CuNi HDAs表面的C-C耦合反应势能较低,有利于*OCCHO中间体的快速生成,从而使乙醇产物的选择性大幅提升.综上,本文以理论计算模拟为指导,以UiO-66-NH2材料为基底,成功设计并制备了一种具有不对称电子结构的CuNi HDAs光催化材料,实现了高选择性CO_(2)光还原为乙醇.研究表明,CuNi HDAs的不对称结构在促进分子活化和降低C-C耦合反应能垒中起关键作用,同时促进了光生电子在CuNi HDAs活性位的富集.本文的研究结果为在原子尺度上设计并合成高性能的CO_(2)还原光催化剂提供了实验和理论参考.
The photocatalytic reduction of CO_(2)to ethanol has attracted extensive attention,particularly for intricate C-C coupling.In this study,we propose a synthetic pathway for asymmetric CuNi heteronuclear diatoms(CuNi HDAs)by anchoring single Cu atoms on the Ni sites of(Ni,Zr)-UiO-66-NH2 to enhance C-C coupling.Cu-(Ni,Zr)-UiO-66-NH2 efficiently performs photocatalytic CO_(2)conversion with a mass-specific activity(selectivity)of 3218μmol·gCu^(-1)·h^(-1)(97.3%).Spectroscopic analyses and density functional theory calculations revealed that CuNi HDAs with an asymmetric electronic distribution facilitated the activation of CO_(2)molecules and lowered the C-C coupling barrier energy,thus promoting the formation of*OCCHO intermediates.This,in turn,led to a significant enhancement of ethanol selectivity.Furthermore,with interfacial Cu-Ni-O bonds as a rapid electron transport channel,CuNi HDAs enrich enough electrons for 12-electron CO_(2)reduction,thereby enhancing ethanol productivity.This study provides a novel strategy for designing highly selective photocatalysts for CO_(2)conversion at the atomic scale.
作者
崔恩田
鲁玉莲
江吉周
Arramel
王定胜
翟天佑
Entian Cui;Yulian Lu;Jizhou Jiang;Arramel;Dingsheng Wang;Tianyou Zhai(Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province,Yancheng Institute of Technology,Yancheng 224051,Jiangsu,China;School of Environmental Ecology and Biological Engineering,School of Chemistry and Environmental Engineering,Key Laboratory of Green Chemical Engineering Process of Ministry of Education,Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education,Novel Catalytic Materials of Hubei Engineering Research Center,Wuhan Institute of Technology,Wuhan 430205,Hubei,China;Department of Chemistry,Tsinghua University,Beijing 100084,China;State Key Laboratory of Material Processing and Die&Mould Technology,School of Materials Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,Hubei,China;Nano Center Indonesi1,Jalan Raya PUSPIPTEK,South Tangerang,Banten 15314,Indonesia)
基金
国家自然科学基金(62004143)
湖北省重点研发计划(2022BAA084)。
