Electro-assisted methane oxidation to formic acid via in-situ cathodically generated H 2 O 2 under ambient conditions.

Direct partial oxidation of methane to liquid oxygenates has been regarded as a potential route to valorize methane. However, CH 4 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 μmol h -1 ) with selective HCOOH production. Mechanistic analysis reveals that reactive oxygen species such as ∙OH and ∙OOH radicals are produced and activate CH 4 and CH 3 OH. In addition, unstable CH 3 OOH generated from methane partial oxidation can be additionally reduced to CH 3 OH on the cathode, and so-produced CH 3 OH is further oxidized to HCOOH, allowing selective methane partial oxidation.