To mitigate the climate impacts of methane, there has been substantial interest in the complete oxidation of methane to carbon dioxide by using photocatalysis at ambient temperatures. However, previous studies have primarily examined methane concentrations well above those found at most emission sources and have overlooked the role of realistic humidity. This work reports methane oxidation rates at 25 °C for oxide-based photocatalysts for methane concentrations ranging from 2 to 5000 ppm. Even under dry conditions with less than 2% relative humidity, residual water attracted to the hydrophilic surfaces of these photocatalysts severely inhibits methane oxidation. Thinning this water layer boosts methane oxidation rates by up to 1 order of magnitude. Furthermore, surface modification of titanium dioxide with a hydrophobic fluorosilane coating (1H,1H,2H,2H-perfluorooctyltriethoxysilane) enables room temperature photocatalytic removal of dilute methane even under conditions with up to 80% relative humidity. These findings and engineering solutions offer guidance for the development of light-driven approaches for scalable methane removal.
Kessler et al. (Tue,) studied this question.