Plasma-modified C-doped Co3O4 nanosheets for the oxygen evolution reaction designed by Butler–Volmer and first-principle calculations

Abstract

Electrocatalysts serving in electrochemical cells differ from general chemical catalysts by way of their special double-layer structure and a rarely discussed interface potential drop as described by the Butler–Volmer (BV) equation. In the present study, we explored the relationship between a material's properties and electrocatalytic performance for the oxygen evolution reaction (OER) by combining the BV equation with first-principle calculations, and concluded that the band gap and conductivity of the material function as descriptors of its electrocatalytic activity as well as Gibbs adsorption free energy. Furthermore, 13 kinds of modification methods, all aimed at developing an earth-abundant catalyst Co₃O₄ with heteroatoms doped in three different crystal sites, were designed and evaluated by a series of predictive first-principle calculations. Special attention was focused on modification with carbon element doping, which notably narrowed the band gap, lowered the polaron migration barrier, and reduced the Gibbs free energy. The selected configuration of the modified electrocatalyst was accomplished by plasma-enhanced chemical vapor deposition with a low-energy input to assure the appropriate doping site of carbon atoms. A remarkable catalytic activity of 235 mV overpotential at 10 mA cm⁻² for OER on carbon-doped Co₃O₄ nanosheets demonstrated the rationality and feasibility of theoretical prediction by comparing this performance with that of the unmodified sample of 423 mV. The theoretical study and calculation prediction proposed here, which is also applicable for other catalysts and even other electrochemical reactions would be helpful for designing new materials or novel modification methods via reducing the failure rate and cost.