Increased Photocatalytic Activity of TiO2 Nanoparticles with Defects for Sustainable Hydrogen Production

Hydrogen gas is touted as a clean-burning energy carrier that can be used in fuel cells for stationary and transportation power at higher efficiency than conventional internal combustion engines. The primary source of H₂today is from nonrenewable natural gas-derived methane steam reforming (MSR). MSR suffers from being a highly endothermic and endergonic reaction (though less so than water splitting), requiring significant energy input as heat generated from burning half of the feed methane, limiting atom efficiency and emitting greenhouse gases. Photocatalytic MSR circumvents the high heat requirement and lowers the reaction temperature, thereby avoiding coke buildup problems as well.

Titanium dioxide (TiO₂) is of particular interest in photocatalysis due to its high photoactivity under ultraviolet illumination and its stability under catalytic reaction conditions. Together with supported metal nanoparticles, TiO₂has been used to catalyze a number of important chemical and photochemical reactions.

We have synthesized defect-rich anatase TiO₂ that shows unique selectivity for hydrogen formation from methane. We have also demonstrated that ultra-violet light illumination boosts the activity and selectivity of the catalyst for hydrogen formation. We have demonstrated hydrogen yield of 27% under steady state conditions using a nickel cocatalyst. Through a combination of experimental and computational techniques, we investigate the mechanisms of defect formation and how these defects activate methane and selectively catalyze hydrogen formation.