(560cm) Electrochemical Oxidation of Methane at Platinum Electrodes Under Ambient Conditions

Electrochemical oxidation of methane is a potential alternative route towards the production of higher value oxygenates such as methanol, formaldehyde, and formic acid. Compared to traditional catalytic processes such as methane steam reforming and Fischer-Tropsch reactions that operate at high temperatures and pressures, electrochemical oxidation of methane has the benefit of operating at near ambient conditions. However, there are still many challenges associated with electrochemical methane oxidation including catalyst activity and selectivity. Previous work has established platinum as one of the few catalysts able to oxidize methane electrochemically. In the present work the electrochemical conversion of methane to CO₂ on platinum electrodes under ambient conditions was investigated. Through a combination of experimentation, density functional theory (DFT), and micro-kinetic modeling, we have developed an improved understanding of the reaction mechanism and the factors that determine catalyst activity. We hypothesize that the methane activation step is a thermochemical process, not electrochemical, as there is only weak potential dependence, if any. Micro-kinetic models that assume thermochemical methane activation as a rate limiting step match well with experimental results. We expanded our microkinetic model to include other transition metals via a descriptor-based analysis and found platinum to be the most active catalyst for the reaction, in line with previously published experimental observations.