Enhancing Oxygen Evolution Reaction Performance of Metal-Organic Frameworks through Cathode Activation.

Abstract

Due to their abundant active sites and porous structures, metal-organic frameworks (MOFs) have garnered significant interest as oxygen evolution reaction (OER) electrocatalysts. Nevertheless, the development of MOF-based electrocatalysts with efficient OER activity and excellent stability simultaneously still faces challenges. Herein, a cathodic activation strategy was used to enhance the OER electrocatalytic performance of M-HHTP for the first time, where M refers to Ni, Cu, Co, Fe, while HHTP denotes 2, 3, 6, 7, 10, 11-hexahydroxytriphenylene. As a prototype, the activated Ni-HHTP (HA-Ni-HHTP) demonstrates outstanding OER performance, with an overpotential as low as 140 mV at 20 mA cm-2 and a small Tafel slope of 78.7 mV-1, surpassing commercial RuO2 and rivaling state-of-the-art MOFs-based electrocatalysts. Characterizations and density functional theory calculations reveal that the superior performance of HA-Ni-HHTP is primarily ascribed to changes in semiconductor type, contact angle, and oxygen vacancy content induced by cathodic activation. Electrochemical impedance spectroscopy analysis using the transmission line model confirms that cathodic activation accelerates charge transport, enhancing the OER process. Furthermore, the cathodic activation strategy holds promise for improving the water oxidation performance of other MOFs such as Fe-HHTP, Co-HHTP, and Cu-HHTP.