Efficient Electrooxidation of Methane to Formic Acid by Optimizing Both the Inner-Sphere and Outer-Sphere Reactions

Abstract Electrooxidation CH4 into valuable, easily transportable liquid fuels offers a highly promising route for the energy-efficient use of CH4. However, achieving high apparent Faradaic efficiency (aFE) and product formation rate is challenging. In this work, we report a heterogeneous WO3 modified Bi (WO3-Bi) incorporated with homogeneous Fe2+ catalytic system in 0.1 M HClO4, which can efficiently electrooxidation CH4 into HCOOH by O2 at the cathode. The aFE of HCOOH can reach up to 96.0%, and the formation rate of HCOOH is 7.9 μmol h–1 cm–2. Experiments and theoretical calculations indicate that the WO3 can not only improve the formation of H2O2 from O2 by enhancing the adsorption of *OOH but also promote the decomposition of H2O2 into •OH radicals by tuning the hydrogen-bond structure of interfacial H2O. The synergy between these two parts facilitates the oxidation of CH4 into HCOOH.