Photocatalytic and optical properties of (Mg:La) CaTiO3: Insights from first principles studies

Abstract

Calcium titanate (CaTiO3) is widely employed in optoelectronic devices and the ceramic industry. The photocatalytic properties of calcium titanate are affected by substitution with transition metals. In this study, the simultaneous inclusion of Mg and La in CaTiO3 was investigated using density functional theory and the generalized gradient approximation functional of Perdew–Burke–Erzenhoff. Including elements had important effects on the structural, photocatalytic, optical, and electronic properties of semiconductor materials. Mg and La were introduced at the calcium sites at a ratio of 2:1. The effects of including Mg and La on the band structure, structural parameters, and optical properties, such as the absorption, static dielectric constant, and reflectivity, were elucidated in detail and clear correlations were also established between them. Co-doping had significant effects on the structural and electronic parameters. The band gap increased due to occupation of states in the conduction band. The static dielectric function decreased from 6 to 3.2, and the static refractive index with doping was 1.8. The reflectivity decreased from less than 20% in case of pure CaTiO3 to less than 10% with co-doping. Clear correlations were established between the electronic properties, such as the band gap and lattice parameter, and the optical properties in order to understand the results obtained. Water splitting was investigated for the pure and doped CaTiO3 in the ultraviolet and visible ranges. Pure and (Mg, La)–CaTiO3 exhibited oxygen evolution reaction activity. The materials are clearly lead-free and suitable for green energy applications because of their photocatalytic activities, and they also have an ideal band gap range for solar cell applications.