Boost of trace methane photo-oxidation in the presence of water vapor via the interfacial hydrophobic effect

The study of water resistance of methane photo-oxidation catalysts is important and challenging for the removal of methane from the atmosphere. Herein, we investigate the mechanistic role of water in the photocatalytic oxidation of trace methane on ZnO decorated with various metal (Cu, Pt). We found that suppressing water dissociation at active sites mitigates hydroxyl-induced catalyst poisoning. Critical insight reveals that photo-generated holes (h⁺) mediate the conversion of passivating hydroxyl groups (OH*) into reactive hydroxyl radicals (•OH), simultaneously liberating active sites and promoting the reaction. In addition, temperature-dependent experiments revealed that increasing the temperature from 20 to 80 °C enhanced the methane conversion by approximately 4-fold, proving that partial desorption of water molecules from the catalyst surface releases active sites. The experimental results show that 0.5 % Pt/ZnO is about 2-fold more water resistant than 0.5 % Cu/ZnO. These findings provide valuable experience and guidance for both mechanistic understanding of water-mediated methane photooxidation and rational design of high-performance catalysts.