Self-activated Rh-Zr mixed oxide as a nonhazardous cocatalyst for photocatalytic hydrogen evolution

Efficient, robust and environmentally friendly cocatalysts for photocatalysts are important for large-scale solar hydrogen production. Herein, we demonstrate that a Rh-Zr mixed oxide is an efficient cocatalyst for hydrogen evolution. Impregnation of Zr and Rh precursors (Zr/Rh = 5 wt/wt%) formed RhZrO cocatalyst particles on Al-doped SrTiO₃, which exhibited 31× higher photocatalytic water-splitting activity than a RhO cocatalyst. X-ray photoelectron spectroscopy proved that the dissociation of Cl^- ions from preformed Rh-Cl-Zr-O solid led to formation of the active phase of RhZrO , in which the Zr/Rh ratio was critical to high catalytic activity. Additional CoO loading as an oxygen evolution cocatalyst further improved the activity by 120%, resulting in an apparent quantum yield of 33 (±4)% at 365 nm and a long durability of 60 h. Our discovery could help scale up photocatalytic hydrogen production.