Electro-Oxidation of Methane on Platinum under Ambient Conditions

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