Unfading TiO2 Photocatalyst Star Materials: Scandium Doping for Enhanced Photocatalytic Overall Water Splitting
Titanium dioxide (TiO2) remains a benchmark photocatalyst for solar-driven overall water splitting (OWS) since its seminal demonstration in 1972. However, practical deployment is constrained by quantum efficiencies below 2% under ambient conditions without sacrificial agents, primarily due to rapid charge recombination mediated by deep-trap defect states (e.g., Ti3+) and weak built-in electric fields. This analysis examines a recent breakthrough by Liu and co-workers (J. Am. Chem. Soc.) that employs 5% scandium (Sc) doping into rutile-phase TiO2 via a molten salt method. The Sc3+ incorporation minimizes deep-level defects and establishes a robust built-in electric field, markedly enhancing charge separation and hydrogen evolution efficiency. Comparative studies with undoped and aluminum-doped TiO2 underscore the specificity of Sc doping. The findings highlight a viable structural modification strategy to overcome intrinsic limitations of TiO2, offering a pathway toward efficient, Earth-abundant photocatalytic systems for green hydrogen production. This advance addresses the critical bottleneck of charge carrier dynamics, potentially enabling quantum yields beyond the 2% threshold and facilitating scalable solar-to-fuel conversion.