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(x) cocatalyst particles on Al-doped SrTiO(3), which exhibited 31× higher photocatalytic water-splitting activity than a RhO(x) 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(x), in which the Zr/Rh ratio was critical to high catalytic activity. Additional CoO(x) 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.