Constructing oxygen vacancy-regulated cobalt molybdate nanoflakes for efficient oxygen evolution reaction catalysis

Abstract

Oxygen evolution reaction (OER) is the dominant step for plenty of energy conversion and storage technologies. However, the OER suffers from sluggish kinetics and high overpotential due to its complex 4-electron/proton transfer mechanism. Thus, developing efficient electrocatalysts is particularly urgent to accelerate OER catalysis but still remains a great challenge. Herein, we have synthesized the novel cobalt molybdate nanoflakes (CoMoO4-Ov-n@GF) with adjustable oxygen vacancies contents by in situ constructing CoMoO4 nanoflakes on graphite felt (GF) and annealing treatment under the reduction atmosphere. The best-performing CoMoO4-Ov-2@GF with optimal oxygen vacancies content shows splendid electrocatalytic performance with the low overpotential (296 mV at 10 mA cm−2) and also small Tafel slope (62.4 mV dec−1) in alkaline solution, which are comparable to those of the RuO2@GF. The experimental and the density functional theory calculations results reveal that the construction of optimal oxygen vacancies in CoMoO4 can expose more active sites, narrow the band-gap to increase the electrical conductivity, and modulate the free energy of the OER-related intermediates to accelerate OER kinetics, thus improving its intrinsic activity.