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

Calcium titanate (CaTiO3) has attracted interest as a photocatalyst for overall water splitting, but its efficiency remains limited. In this study, CaTiO3 powders codoped with aluminum (Al3+), scandium (Sc3+), and magnesium (Mg2+) 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 (Ti4+). Appreciable particle growth was observed in the Al3+-doped sample. Codoping with Sc3+ significantly reduced particle size but also lowered crystallinity, which hindered photocatalytic activity. Further codoping with Mg2+ effectively suppressed the formation of deep-level defects. As a result, the CaTiO3 powder codoped with Al3+, Sc3+, and Mg2+ (CaTiO3: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 CaTiO3 itself. Transient absorption measurements revealed enhanced carrier reactivity due to trap state modulation and improved lifetimes in the CaTiO3:Al,Sc,Mg sample. Band alignment studies indicated that CaTiO3 has a more negative conduction band minimum than that of strontium titanate (SrTiO3). These findings demonstrate that strategic doping significantly enhances the photocatalytic properties of CaTiO3 for various reactions.