Facet-engineered SrTiO3:Rh via solid-state ionic doping for efficient Z-scheme overall water splitting
Facet-engineered semiconductor single crystals hold considerable promise for applications ranging from solar fuels to photovoltaics. However, solid-state syntheses, though operationally simpler, typically fail at facet control due to limited atomic mobility, whereas solution/flux-based methods rely heavily on additives. Herein, we report a straightforward, self-directing solid-state ion doping strategy for synthesizing well-defined cuboidal rhodium-doped SrTiO 3 (SrTiO 3 :Rh) single-crystalline particles with predominant (1 0 0)/(0 1 0) facet exposure. This strategy is based on the identification of a previously unrecognized dual role of ionic Rh precursors as intrinsic structure-directing agents and visible-light sensitizers, facilitating concurrent crystal growth, facet stabilization and controlled doping incorporation during a single calcination step. Compared to Rh 2 O 3 -derived SrTiO 3 :Rh, a milestone photocatalyst historically suffered from poor facet control, these cuboidal crystals with anisotropic electronic surface structures exhibited enhanced crystallinity, superior charge separation efficiency and accelerated surface reaction kinetics, resulting in an order-of-magnitude improvement in visible-light-driven hydrogen evolution. Notably, when integrated into a liquid-phase Z-scheme system with BiVO 4 and Fe 3+ /Fe 2+ redox mediators, the SrTiO 3 :Rh single crystals exhibited a remarkable apparent quantum yield of 3.2 % at 420 nm for overall water splitting. This facile, self-directing synthetic approach addresses key challenges in traditional solid-state routes, providing valuable guidance for rational facet and doping engineering in diverse functional semiconductors for energy conversion.
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