摘要
缺陷位点的引入可以通过增加对反应中间体的亲和力来提高催化剂的催化能力.纳米材料中存在多种缺陷类型,如阳离子缺陷和阴离子缺陷.不同的缺陷位点对电催化性能的贡献不同.因此,构筑缺陷必须精准、明确,以便于确定最优的缺陷类型,促进电化学反应.在这项工作中,我们以钴空位为例,分别成功合成了二价钴空位(Co3O 4-VCo(II))和三价钴空位(Co_(3)O_(4)-VCo(III))的Co_(3)O_(4).电化学结果表明,钴空位的引入可以显著提高Co_(3)O_(4)的电催化性能.Co_(3)O_(4)-VCo(II)表现出最突出的析氧反应(OER)性能,反应动力学速率最快.X射线光电子能谱分析表明,在OER过程中,VCo(II)的存在可以使CoOOH活性位点快速形成.密度泛函理论计算表明,钴空位的引入使Co_(3)O_(4)拥有类似金属的导电性.VCo(II)的存在使得O p带中心靠近费米能级,自由能势垒降低,电催化剂表面氧交换动力学速率加快,对反应中间体的吸附能最佳,从而表现出优异的电化学性能.本研究为设计高效的富缺陷电催化剂提供了重要指导.
The introduction of defect sites has been widely reported to enhance electrocatalysts' abilities by increasing their affinity for reaction intermediates. Many different defect types, such as cation and anion vacancies, can exist in nanomaterials. The different defect sites can make different contributions to the electrochemical ability. Therefore, a constructed defect should be accurate and specific, which makes it easy to identify the optimal defect type to facilitate electrochemical reactions. In this work, we used cobalt vacancies in Co_(3)O_(4) as an example and synthesized Co_(3)O_(4) with bivalent cobalt vacancies(Co_(3)O_(4)-VCo(II)) and trivalent cobalt vacancies(Co_(3)O_(4)-VCo(III)). Electrochemical results demonstrate that introducing cobalt vacancies considerably enhances the electrocatalytic activity of Co_(3)O_(4). Furthermore, Co_(3)O_(4)-VCo(II) exhibits the most outstanding oxygen evolution ability with the fastest reaction kinetic rate. Quasi-operando X-ray photoelectron microscopy spectrum analysis results indicate that the presence of VCo(II) can accelerate CoOOH active site formation during the oxygen evolution reaction process. Density functional theory calculations reveal that introducing cobalt vacancies can endow Co_(3)O_(4) with metal-like conductivity. The O p-band center can be moved near the Fermi level, and the free energy barrier can be the lowest with the presence of VCo(II), resulting in a fast kinetics rate of oxygen exchange at the electrocatalyst surface and optimal adsorption energy to reaction intermediates to display excellent electrochemical ability. This work provides substantial guidance for designing efficient defect-rich electrocatalysts.
作者
刘志娟
汪广进
郭锦瑜
王燕勇
Zhijuan Liu;Guangjin Wang;Jinyu Guo;Yanyong Wang(State Key Laboratory of Chem/Bio-sensing and Chemometrics,College of Chemistry and Chemical Engineering,Hunan University,Changsha 410082,China;Henan Key Laboratory of Molecular Functional Materials,Henan International Joint Laboratory of Tumor Theranostical Cluster Materials,Green Catalysis Center,and College of Chemistry,Zhengzhou University,Zhengzhou 450001,China;School of Materials Science and Energy Engineering,Foshan University,Foshan 528000,China)
基金
supported by the National Natural Science Foundation of China (22272047, 21905088, and 22102155)
China Postdoctoral Science Foundation (2021M692909 and 2022T150587)
the Provincial Natural Science Foundation of Hunan (2022JJ10006)。
