Superior photocatalytic activity of Pt-loaded rutile-type TiO2 particles in brine splitting reaction

Abstract

A Pt-loaded rutile-type TiO₂ photocatalyst was investigated for splitting brine (aqueous NaCl solution) into hydrogen and chlorine as a new artificial photosynthesis reaction. Although most of Pt species dissolved in solution during induction period, the small amount of Pt remaining on the TiO₂ surface was active and stable, resulting in continuous hydrogen and chlorine production for 40 h at a catalytically sufficient turnover number. The photocatalytic activity of Pt-loaded TiO₂ increased to more than 10 times the previously reported value, and the quantum efficiency and solar energy conversion efficiency reached 4.3 % at 365 nm and 0.07 %, respectively. Notably, this activity is also higher than that reported for one-step pure water splitting reactions using TiO₂-based photocatalysts. Although chlorine production is thermodynamically more challenging than the oxygen evolution reaction, chlorine production involving a two-electron oxidation process is more kinetically favorable than oxygen production involving a four-electron oxidation process, which is considered as the rate-determining step. Our findings open a new direction for brine splitting and also enrich the field of artificial photosynthetic reactions.