Tailoring of electrocatalytic oxygen evolution reaction performance of 2D conductive Co-catecholate metal-organic frameworks

Abstract

Herein, we report the microwave hydrothermal synthesis of highly porous and conductive 2D Co-catecholate MOFs (Co-CATs) in the absence (Co-CAT-WO) and presence (Co-CAT-W) of N-methyl-2-pyrrolidone (NMP) polar solvent, and the study of these Co-CATs as electrocatalysts for oxygen evolution reaction (OER). The OER performance of Co-CAT-WO and Co-CAT-W is compared. The as-synthesized Co-CATs exhibit a 2D layered hexagonal structure. The electrical conductivity of Co-CAT-WO and Co-CAT-W is 6.9 and 5.8 S/m, respectively. The good conductivity and porous structure can initiate charge transport to achieve better OER performance under the 4e^--transfer process. The as-prepared Co-CAT-WO and Co-CAT-W, respectively, show an overpotential of 455 and 424 mV at 10 mA/cm² after performing the durability and chronoamperometry experiments for 13 h in 1 M KOH. From the electrochemical studies, it is apparent that the Co-CAT-W exhibits better OER performance with low overpotential, high current density, and excellent stability over extended cycling. Moreover, the lower HOMO-LUMO gap for Co-CAT-W than that of the Co-CAT-WO endorses its better electrocatalytic activity. The post-OER results show that the Co-CAT-W electrocatalyst acts as a "precatalyst" rather than the original catalyst, and it undergoes electrochemical transformation to metal hydroxide and metal oxyhydroxide after the OER studies, promoting the OER kinetics. The findings of this work offer valuable insights into the synthetic strategies for developing 2D conducting metal-catecholate MOF catalysts for efficient and sustainable OER processes, which is crucial in water splitting for sustainable energy production.