Investigating the Metal–TiO₂ Influence for Highly Selective Photocatalytic Oxidation of Methane to Methanol

Abstract

Methane conversion to valuable chemicals is a highly challenging and desirable reaction. Photocatalysis is a clean pathway to drive this chemical reaction, avoiding the high temperature and pressure of the syngas process. Titanium dioxide, being the most used photocatalyst, presents challenges in controlling the oxidation process, which is believed to depend on the metal sites on its surface that function as heterojunctions. Herein, we supported different metals on TiO 2 and evaluated their activity in methane photooxidation reactions. We showed that Ni−TiO 2 is the best photocatalyst for selective methane conversion, producing impressively high amounts of methanol (1.600 μmol•g −1 ) using H 2 O 2 as an oxidant, with minimal CO 2 evolution. This performance is attributed to the high efficiency of nickel species to produce hydroxyl radicals and enhance H 2 O 2 utilization as well as to induce carrier traps (Ti 3+ and SETOVs sites) on TiO 2 , which are crucial for C−H activation. This study sheds light on the role of catalyst structure in the proper control of CH 4 photoconversion.