Highly efficient ambient temperature photo-oxidation of CH4 to C1 products over CeO2 supported single-atom Fe with oxygen vacancies

Abstract

The direct conversion of methane (CH₄) to high-value liquid products is of significant importance to address the current environmental and energy crises. Here, we show a kind of CeO₂-supported oxygen vacancy (O_v) bound, Fe single-atom catalyst (SAC) that can enable exceptional photocatalytic CH₄ conversion to C₁ oxygenates with nearly 100% selectivity at ambient temperature. Under optimized experimental conditions, a C₁ product yield of 3420 mmol g_Fe⁻¹ h⁻¹ was realized, largely outperforming a previously reported Rh/CeO₂ SAC (1232 mmol g_Rh⁻¹ h⁻¹ with an oxygenate selectivity of 94%). DFT calculation and experimental investigation are coupled to reveal the mechanism of CH₄ conversion. Essentially, single Fe sites serve as electron acceptors and effectively promote photo-induced electron transfer from Ce to Fe via the formed Ce–O–Fe bond, while O_v-induced Ce³⁺ sites facilitate the adsorption and activation of H₂O₂ to produce ˙OH, which further activates CH₄ and generates various products. The participation of O_v during the catalytic cycle and its synergy with single Fe sites largely boost the overall efficiency of CH₄ conversion.