Metal-Organic Frameworks with Assembled Bifunctional Microreactor for Charge Modulation and Strain Generation toward Enhanced Oxygen Electrocatalysis

作者：He, Fan; Zhao, Yingjie; Yang, Xiaoxuan; Zheng, Sixing; Yang, Bin; Li, Zhongjian; Kuang, Yongbo; Zhang, Qinghua; Lei, Lecheng; Qiu, Ming^*; Dai, Liming^*; Hou, Yang^*

来源：ACS Nano, 2022, 16(6): 9523-9534.

DOI：10.1021/acsnano.2c02685

• metal-organic frameworks
• bifunctional microreactor
• tensile strain
• spin and charge regulation
• accelerated reaction kinetics

Two-dimensional metal-organic frameworks (MOFs) have served as favorable prototypes for electrocatalytic oxygen evolution reaction (OER). Despite promising catalytic activity, their OER reaction kinetics are still limited by the sluggish four-electron transfer process. Herein, we develop a terephthalic acid (CoBDC) catalyst with a bifunctional microreactor composed of two species of Co active sites and ligand FcCA (CoBDC FcCA). Benefiting from the ultrathin nanosheet structure, CoBDC FcCA catalyst exhibits an excellent OER performance with a low overpotential of 280 mV to reach 10 mA cm-2 and a small Tafel slope of 53 mV dec-1. Structure characterization together with theoretical calculations directly unravel the coordination for two species of Co active moieties with FcCA forming a microreactor of tensile strain, leading to a conversion of the Co spin from a high spin state (t2g5eg2) to an intermediate spin state (t2g6eg1) to regulate antibonding states of Co 3d and O 2p orbital. In situ spectroscopic measurements for mechanistic understanding reveal that this CoBDC FcCA catalyst possesses an optimal OH* adsorption energy for propitious formation of O-O bonds in the OOH* intermediate, thus effectively decreasing the thermodynamic Gibbs free energy of the rate-determining step (O* -> OOH*) to accelerate reaction kinetics for the whole OER process. When loaded on an integrated BiVO4 photoanode as a cocatalyst, CoBDC FcCA enables highly active solar-driven oxygen production from water splitting. KEYWORDS: metal-organic frameworks, bifunctional microreactor, tensile strain, spin and charge regulation, accelerated reaction kinetics

• 单位
  中国科学院; 中国科学院宁波材料技术与工程研究所; y; 浙江大学