Simultaneous Photodeposition of a Ni–Mo Cocatalyst on Calcium Titanate for Efficient Photocatalytic Water Splitting

Precise cocatalyst design is essential to maximize the efficiency of particulate photocatalysts for solar-driven water splitting. Here, we demonstrate that a precious-metal-free Ni–Mo dual-element cocatalyst significantly enhances the overall water-splitting activity of calcium titanate CaTiO3 microcrystals while systematically elucidating its structural and functional properties. Through simultaneous photodeposition (SPD), a NiO–MoO2 composite and MoO3 species are site-selectively deposited onto the reductive and oxidative facets of polyhedral CaTiO3, respectively. During water splitting under Hg lamp irradiation, the reductive-facet NiO–MoO2 composite is reduced and drives hydrogen evolution, achieving an H2 production rate that is 253-fold and 6.7-fold higher than those of pristine CaTiO3 and the Ni-only counterpart, respectively. Although the presence of Ni species on oxidative facets slightly suppresses water oxidation, the reduced NiO–MoO2 composite on the reductive facet is expected to facilitate photogenerated electron utilization and reduce charge recombination, thereby boosting overall performance. These findings demonstrate a simultaneous photodeposition strategy for precious-metal-free functional cocatalyst architectures in solar-to-chemical energy conversion.