Flux-Assisted Syntheses of Calcium Titanate Powders Codoped with Aluminum, Scandium, and Magnesium for Efficient Photocatalytic Overall Water Splitting

Calcium titanate (CaTiO 3 ) has attracted interest as a photocatalyst for overall water splitting, but its efficiency remains limited. In this study, CaTiO 3 powders codoped with aluminum (Al 3+ ), scandium (Sc 3+ ), and magnesium (Mg 2+ ) cations were synthesized via a flux-mediated method. XRD and Raman analyses confirmed the formation of single-phase perovskite structures with successful dopant incorporation at the B-site (Ti 4+ ). Appreciable particle growth was observed in the Al 3+ -doped sample. Codoping with Sc 3+ significantly reduced particle size but also lowered crystallinity, which hindered photocatalytic activity. Further codoping with Mg 2+ effectively suppressed the formation of deep-level defects. As a result, the CaTiO 3 powder codoped with Al 3+, Sc 3+, and Mg 2+ (CaTiO 3:Al,Sc,Mg) exhibited the highest photocatalytic activity, achieving an apparent quantum yield (AQY) of 73.8% (at 310 nm). Durability tests showed that degradation occurred primarily on the loaded cocatalysts, not the CaTiO 3 itself. Transient absorption measurements revealed enhanced carrier reactivity due to trap state modulation and improved lifetimes in the CaTiO 3:Al,Sc,Mg sample. Band alignment studies indicated that CaTiO 3 has a more negative conduction band minimum than that of strontium titanate (SrTiO 3 ). These findings demonstrate that strategic doping significantly enhances the photocatalytic properties of CaTiO 3 for various reactions.