Tuning electrochemical transformation process of zeolitic imidazolate framework for efficient water oxidation activity

Abstract

Metal-organic frameworks (MOFs) have been widely studied as efficient electrocatalysts for water oxidation due to their tunable structure and easy preparation. However, the rational design of MOFs-based electrocatalysts and fundamental understanding of their structural evolution during oxygen evolution reaction (OER) remain critical challenges. Here, we report a facile approach to tune the structural transformation process of the Co-based zeolitic imidazolate framework (ZIF) during the OER process by using water molecules as a vacancy promoter. The modified ZIF catalyst accelerates the structural transformation from MOF precursor to electrochemical active species and simultaneously enhances the vacancy density during the electrochemical activation process. The optimized electrocatalyst exhibits an extremely low overpotential 175 mV to deliver 10 mA cm−2 and superior durability (100 h) at 100 mA cm−2. The comprehensive characterization results reveal the structural transformation from the initial tetrahedral Co sites to cobalt oxyhydroxide (CoOOH) and the formation process of oxygen vacancies (CoOOH-VO) at a high anodic potential. These findings represent a promising way to achieve highly active MOF-based electrocatalysts for water oxidation.