Enhanced Interfacial Properties of Nafion-Coated Mg/TiO2 with (101) Anatase Facet for Photocatalytic CO2 Reduction

Addressing the continual rise in atmospheric CO₂ levels is a pressing challenge. Developing sustainable methods to convert CO₂ into valuable products is crucial for mitigating global warming and meeting long-term energy demands. The development of novel photocatalysts and the use of solar energy via photocatalysis are key to achieving CO₂-to-CH₃OH conversion. Among these, TiO₂ anatase has shown significant results for photocatalytic CO₂ reduction; however, its high bandgap energy restricts its efficiency in utilizing visible wavelengths, highlighting the need for further optimization. By doping strategy with alkaline earth metal like Mg, it modified the electronic properties of anatase TiO₂ and introduced more Lewis basic sites. Furthermore, Nafion coating facilitates proton-coupled electron transfer (PCET), stabilizes intermediates, and prevents methanol back-oxidation. Under UV–Vis irradiation for 8 h, the CH₃OH yield from the photocatalytic CO₂-to-CH₃OH by Nafion/Mg–TiO₂ is 1559.82 μmol⁻¹ g⁻¹ h⁻¹, outperforming Mg–TiO₂ (1350.20 μmol⁻¹ g⁻¹ h⁻¹) and pristine TiO₂ (930.96 μmol⁻¹ g⁻¹ h⁻¹). Langmuir–Hinshelwood (L–H) kinetic model reveals that CO is an intermediate product in this process, where its subsequent reaction with oxygen produces CH₃OH, marking the rate-determining step. The synergistic effect of Nafion and Mg doping in TiO₂ optimizes acid–base interfaces contributed by Lewis’s base and acidic protonated Nafion, enabling efficient charge separation and enhanced photocatalytic activity. Nafion/Mg–TiO₂ is a promising platform for designing advanced photocatalysts for CO₂ reduction to methanol.