Humidity-Tolerant Photocatalysts for Methane Removal

Abstract

To mitigate the climate impacts of methane (CH4), there has been substantial interest in the complete oxidation of CH4 to carbon dioxide using photocatalysis at ambient temperatures. However, previous studies have been conducted on CH4 concentrations well above those present at most emissions sources and have not accounted for realistic humidity. We first report CH4 oxidation rates for oxide-based photocatalysts under dry conditions for CH4 concentrations spanning 2 to 5,000 parts per million. We find that the residual water remaining on these photocatalysts’ hydrophilic surfaces in dry conditions severely inhibits CH4 oxidation, and that when this water layer is thinned, CH4 oxidation rates can be boosted by up to one order of magnitude. We further show that modifying the surface of titanium dioxide with a hydrophobic fluorosilane coating enables dilute CH4 removal under humid conditions. We discuss how these results guide the development of photocatalysts for scalable methane removal.

Keywords: Photocatalytic methane oxidation, reaction kinetics, humidity tolerance, atmospheric methane removal