Electro-Oxidation\nof Methane on Platinum under Ambient\nConditions

Abstract

Herein, we investigate the electrochemical\nconversion of methane\nto CO₂ on platinum electrodes under ambient conditions.\nThrough a combination of experimentation, density functional theory\n(DFT) calculations, and ab initio kinetic modeling, we have developed\nan improved understanding of the reaction mechanism and the factors\nthat determine catalyst activity. We hypothesized that the rate-determining\nmethane activation step is thermochemical (i.e., CH₄(g)\n→ CH₃^* + H^*) as opposed to electrochemical based on a fitted\nbarrier of approximately 0.96 eV that possesses minimal potential\ndependence. We developed a simple kinetic model based on the assumption\nof thermochemical methane activation as the rate-determining step,\nand the results match well with experimental data. Namely, the magnitude\nof the maximum current density and the electrode potential at which\nit is realized agree with our ab initio kinetic model. Finally, we\nexpanded our kinetic model to include other transition metals via\na descriptor-based analysis and found platinum to be the most active\ncatalyst for the oxidation of methane, which is in line with previously\npublished experimental observations.