Tailoring Electrocatalytic Ov-NiOOH by Regulating the Reconstruction in Ni-Based Metal-Organic Frameworks with Highly Asymmetric Ni-O Coordination.

Abstract

Metal-organic frameworks have aroused growing interest in the research of energy conversion and storage. However, their specific configuration, especially the coordination environment of metal active sites, has not been well designed. Their role in regulating the structural reconstruction of pre-electrocatalysts remains ambiguous. Herein, this work reports a dual-ligand strategy to design a Ni-MOF with asymmetric Ni-O coordination, named Ni-BDC-DOBDC, which occupies unsaturated Ni sites and strengthens Ni-O bonds. As inspected by X-ray absorption near edge structure as well as a series of in situ and ex situ characterizations, this special Ni-O coordination contributes to O_v-NiOOH with rich oxygen vacancies during fast self-reconstruction at a lower potential. Moreover, theoretical results reveal that Ni sites in O_v-NiOOH occupy a higher d-band center, a lower adsorption energy barrier, and a more electronic negative surface in the oxygen evolution reaction, leading to good electrocatalytic performance. Overall, Ni-BDC-DOBDC catalysts exhibit a low overpotential of 202 mV at 10 mA cm^-2 and outstanding stability within 240 h. The insights in this work pave the way for high-performance MOF-based catalysts by regulating their self-reconstruction kinetics through a new aspect of asymmetric ligand engineering.