Boosting electrochemical methane conversion by oxygen evolution reactions on Fe–N–C single atom catalysts

Abstract

Electrochemical methane conversion is promising for direct conversion even at ambient temperature, but requires delicate control of the competing reactions of the electrochemical oxygen evolution reaction (OER) to improve efficiency and productivity. Here we employ Fe–N–C single atom catalysts (SACs) to achieve high faradaic efficiency and ethanol conversion productivity in OER-assisted methane oxidation. We computationally identify a potential region that maintains stable active oxygen on Fe–N–C SACs where the potential limiting step for the OER is OOH* formation. We also present a reaction pathway for the spontaneous oxidation of methane by the active oxygen, production of methanol, and conversion to ethanol by deprotonation. The Fe–N–C SAC achieves methane-to-ethanol conversion with a high production rate of 4668.3 μmol g_cat⁻¹ h⁻¹ with a selectivity of 85% under the application of 1.6 V_RHE. The faradaic efficiency (FE) is 68%, far exceeding previous results. Furthermore, we demonstrate a direct gas diffusion flow cell to enhance the mass transfer of methane. Conversion in the flow cell achieves ethanol production rates of up to 11 480.6 μmol g_cat⁻¹ h⁻¹.