Hydrophobic TaO_x Species Overlayer Tuning Light‐Driven Methane Chlorination with Inorganic Chlorine

Abstract Halogenated methane serves as a universal platform molecule for building high‐value chemicals. Utilizing sodium chloride solution for photocatalytic methane chlorination presents an environmentally friendly method for methane conversion. However, competing reactions in gas‐solid‐liquid systems leads to low efficiency and selectivity in photocatalytic methane chlorination. Here, an in situ method is employed to fabricate a hydrophobic layer of TaO_x species on the surface of NaTaO₃. Through in‐situ XPS and XANES spectra analysis, it is determined that TaO_x is a coordination unsaturated species. The TaO_x species transforms the surface properties from the inherent hydrophilicity of NaTaO₃ to the hydrophobicity of TaO_x/NaTaO₃, which enhances the accessibility of CH₄ for adsorption and activation, and thus promotes the methane chlorination reaction within the gas‐liquid‐solid three‐phase system. The optimized TaO_x/NaTaO₃ photocatalyst has a good durability for multiple cycles of methane chlorination reactions, yielding CH₃Cl at a rate of 233 µmol g⁻¹ h⁻¹ with a selectivity of 83%. In contrast, pure NaTaO₃ exhibits almost no activity toward CH₃Cl formation, instead catalyzing the over‐oxidation of CH₄ into CO₂. Notably, the activity of the optimized TaO_x/NaTaO₃ photocatalyst surpasses that of reported noble metal photocatalysts. This research offers an effective strategy for enhancing the selectivity of photocatalytic methane chlorination using inorganic chlorine ions.