Engineering of HO-Zn-N2 Active Sites in Zeolitic Imidazolate Frameworks for Enhanced (Photo)Electrocatalytic Hydrogen Evolution

Abstract

Currently, lack of ways to engineer specific and well-defined active sites in zeolitic imidazolate frameworks (ZIFs) limits our fundamental knowledge with respect to the mechanistic details for (photo)electrocatalytic hydrogen evolution reaction (HER). Here, we introduce the open metal sites into ZIFs through the selective ligand removal (SeLiRe) strategy, comprehensively characterize the altered structural and electronic features, and evaluate their role in HER. In situ electrochemical analysis and X-ray absorption spectroscopy reveal the formation of high-valence HO-Zn-N2 sites through the binding of Zn-N2 with electrolyte hydroxide. The optimal OMS-ZIF exhibits a low overpotential of 0.41 V to achieve an ampere-level 1.0 A cm-2 with 120-hour stability. Theoretical simulations indicate that these active sites accelerate the water molecules activation kinetics, consequently enhancing the efficiency of the Volmer step. This work demonstrates a versatile strategy to introduce highly active catalytic sites in ZIFs, providing new insights into the electrocatalytic mechanism in alkaline media.