Mechanisms of Photocatalytic Molecular Hydrogen and Molecular Oxygen Evolution over La-Doped NaTaO3 Particles: Effect of Different Cocatalysts and Their Specific Activity

Abstract

A better understanding of the mechanisms of H2 and O2 evolution over cocatalyst-loaded photocatalysts is an essential step in constructing efficient artificial systems for the overall water splitting. In this paper, La-doped NaTaO3 particles loaded with different cocatalysts (i.e., noble metals and metal oxides) have been synthesized and used as model photocatalysts to study the mechanisms of photocatalytic H2 and/or O2 evolution from pure water, aqueous methanol solution, and aqueous silver nitrate solution. It was found that the photocatalytic activity and selectivity toward H2 and/or O2 evolution strongly depend on the nature of the cocatalyst and the investigated system. For pure water and aqueous silver nitrate systems, the affinity of the cocatalyst nanoparticles to react with the photogenerated charge carriers (electrons or holes) was found to be the main reason for the observed selective behavior for H2 and O2 evolution. The creation of active sites and subsequent decrease in activation energy is ...