Au-decorated ZnxMg1−xO solid solutions with coexisting acidic and basic sites for enhanced photocatalytic methane conversion to ethane

Abstract

The direct and selective conversion of methane into high-value chemicals such as ethane represents an ideal route for the efficient utilization of natural gas resources. However, this process faces challenges including the difficulty of C–H bond activation and the over-oxidation of products. In this study, a gold nanoparticle-decorated Zn_xMg_1−xO (0 < x ≤ 0.8) solid solution photocatalyst was developed for highly efficient oxidative coupling of methane under mild conditions. The optimized 3Au–Zn_0.95Mg_0.05O catalyst exhibited remarkable performance, achieving an ethane production rate of 2700 µmol g⁻¹ h⁻¹ with 85% selectivity, significantly surpassing that of unmodified catalysts. It was demonstrated that the Zn²⁺ and Mg–OH groups in the Zn_xMg_1−xO solid solution form synergistic Lewis acid–base pairs, which effectively promote CH₄ adsorption and C–H bond activation. Meanwhile, the supported Au nanoparticles not only enhance the separation efficiency of photogenerated charges but also provide stable adsorption sites for ˙CH₃ radicals, thereby effectively suppressing over-oxidation to CO₂. Mechanistic studies confirmed that photogenerated holes and reactive oxygen species (O₂⁻, O⁻) play critical roles in methane activation and C–C coupling. This work presents a novel strategy for designing highly efficient photocatalysts for methane conversion by constructing a synergistic system of acid–base pairs and metal co-catalysts, demonstrating great potential for the valorization of natural gas under mild conditions.