Photocatalytic Methane Steam Reforming to Valorize Point-Source Methane

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 H₂ today 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, avoiding coke buildup. Eliminating the furnace simplifies reactor design and permits application at smaller scale allowing biorenewable methane from landfill gas, anaerobic digestion of food waste, and dairy farms to become a feasible feed stock for MSR. An additional benefit of biomethane utilization is to incentivize point sources such as landfills and dairy farms, to capture the methane, instead of releasing the potent greenhouse gas into the atmosphere.

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, TiO₂ has 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.