Kinetic Coupling of Water Splitting and Photoreforming on SrTiO3-Based Photocatalysts

Abstract

Coupling the proton reduction of overall water splitting with oxidation of oxygenated hydrocarbons (photoreforming) on Al-doped SrTiO3 decorated with cocatalysts enables efficient photocatalytic H2 generation along with oxygenate conversion, while decreasing the accumulation of harmful byproducts such as formaldehyde. Net H2 evolution rates result from the contributions of the individual rates of water oxidation, oxygenate oxidation, and the back-reaction of H2 and O2 to water. The latter reaction is suppressed by a RhCrOx cocatalyst or by high concentrations of oxygenates in the case of Rh cocatalyst, whereas the rates of organic oxidation depend on their molecular structure. In the absence of the back-reaction to water, the H2 evolution rates are independent of the oxygenate type and concentration because the rates of water splitting compensate the variations in the rates of oxygenate conversion. Under such conditions of suppressed back-reaction, the selectivities to water and oxygenate oxidation, both ...