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

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 μmol h^-1) with selective HCOOH production. Mechanistic analysis reveals that reactive oxygen species such as ∙OH and ∙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.