Plasma Electrocatalytic Oxidation of Methane to Methanol.

Selective electrocatalytic conversion of methane (CH4) to methanol (CH3OH) using renewable electricity under ambient conditions offers an option of interest in providing methane-derived molecules that are readily transported. The high thermodynamic stability and chemical inertness of CH4 today limit both the productivity and selectivity. Here, we report a hybrid plasma-electrocatalytic system that enables CH4-to-CH3OH conversion under ambient conditions. By using plasma to preactivate CH4, the challenge transits from electrochemical CH4 oxidation to methyl radical (•CH3) conversion. We document the coupling of short-lived CH3 radicals and adsorbed hydroxyl groups (*OH) at the plasma-catalyst-electrolyte interface. We achieve >90% faradaic efficiency in the electrochemical stage of CH3 radicals to CH3OH conversion and a methanol yield on total electrical energy of 60 gmethanol kWh-1, with plasma energy accounting for 90% of the total electricity. We operated the hybrid plasma-electrocatalytic system for 890 h with an average faradaic efficiency of 86%. This study presents a new radical-based pathway and contributes to activate-and-electrolyze conversion reactions.