Major routes in the photocatalytic methane conversion into chemicals and fuels under mild conditions

Methane is one of the most abundant molecules on Earth. Most of the state-of-the-art methane chemical conversion technologies require high temperatures, they are accompanied by insufficient selectivity, carbon deposition and major production of carbon dioxide. Development of the methane conversion technologies at mild conditions is important for the rational utilization of renewable and fossil feedstocks and for the environment. The goal of this review is to perform a comparative analysis of low temperature methane photocatalytic conversion routes such as methane oxidation, methane reforming and methane coupling. Methane photocatalytic reforming and selective oxidation currently exhibit the highest conversion rates, while methane coupling shows the highest selectivity. The most promising routes could be methane oxidation to methanol, which simultaneously exhibits higher productivity and selectivity. Further improvements in the methane conversion can be achieved by the design of new materials, photoreactors and operating modes, such as photochemical looping and combining photocatalysis with electrocatalysis.