Phase reconstruction of Co3O4 with enriched oxygen vacancies induced by cold plasma for boosting methanol-to-formate electro-oxidation

Abstract

Developing high-performance Pt-free electrocatalysts for the electro-oxidation of methanol (MeOH) into high-value-added formate in alkaline media offers a sustainable avenue for synchronous biomass valorization and MeOH oxidation-assisted hydrogen production. Herein, electrodeposited Co(OH)2 on Ni foam (NF) was treated by an O2 cold plasma to obtain oxygen vacancies enriched Co3O4-x/NF-P. The resultant Co3O4-x/NF-P only requires a potential of 1.318 V vs. RHE to upgrade MeOH into formate at 10 mA·cm−2. Characterization and calculation results reveal that oxygen vacancy induced irreversible phase transformation of Co3O4-x/NF-P, facilitating the deprotonation of MeOH, and suppressing further oxidation of HCOO* for selective and efficient formate electrosynthesis. Impressively, a Co3O4-x/NF-P||Co3O4-x/NF-P pair was built to couple the MeOH electro-oxidation with H2 evolution, where it only supplies a cell voltage of 1.540 V at 10 mA·cm−2 and the anodic Faraday efficiency exceeds 95 %. This work clarifies in-depth insight the underlying mechanism of MeOH selective oxidation into formate.