Electro-assisted methane oxidation to formic acid via in-situ cathodically generated H2O2 under ambient conditions

Abstract

Direct partial oxidation of methane to liquid oxygenates has been regarded as a potential route to valorize methane. However, CH4 activation usually requires a high temperature and pressure, which lowers the feasibility of the reaction. Here, we propose an electro-assisted approach for the partial oxidation of methane, using in-situ cathodically generated reactive oxygen species, at ambient temperature and pressure. Upon using acid-treated carbon as the electrocatalyst, the electro-assisted system enables the partial oxidation of methane in an acidic electrolyte to produce oxygenated liquid products. We also demonstrate a high production rate of oxygenates (18.9 mol h(-1)) with selective HCOOH production. Mechanistic analysis reveals that reactive oxygen species such as center dot OH and center dot OOH radicals are produced and activate CH4 and CH3OH. In addition, unstable CH3OOH generated from methane partial oxidation can be additionally reduced to CH3OH on the cathode, and so-produced CH3OH is further oxidized to HCOOH, allowing selective methane partial oxidation. This study presents the electrochemically assisted partial oxidation of methane to produce liquid oxygenate, HCOOH, selectively which involves in-situ cathodically generated reactive oxygen species with an acid-treated carbon electrocatalyst.