Selective Electrochemical Oxidation of Methane to Ethanol over the Co3O4/La2O2CO3 Heterojunction Catalyst

Abstract

Catalyzing methane (CH₄) at room temperature to value-added products is a promising approach, but high product selectivity remains a challenge. In this study, La₂CoO₃ was used as a precursor to synthesize xLC (xCo₃O₄/La₂CoO₃) by adjusting the molar ratio of Co and La. When glycerol was added for hydrothermal modification, a carbon source was introduced into xLC to form an efficient heterojunction material xLC-C (xCo₃O₄/La₂O₂CO₃) capable of converting CH₄ to ethanol at 2.2 V (vs RHE). Moreover, 3.5LC-C was found to convert CH₄ with a current density difference of up to 17.86 mA/cm² and ethanol yields of 627 μmol/g_cat/h. Density functional theory calculations indicate that the high reactivity results from an increased internal charge distribution following the introduction of La₂O₂CO₃ into the Co₃O₄ system, which provides electron transport and reactive oxygen species to activate the C–H bond. Co₃O₄ serves as the active phase, providing a site for the adsorption and conversion of CH₄. The presence of La₂O₂CO₃ in this study reduces the reaction residence time, thus inhibiting C–C coupling reactions between intermediates such as CH₄ and HCHO, impeding the formation of long-chain alcohols and achieving high product selectivity.