Ab initio design of Zr/Te co-doped XTiO3 (X = Ca, Sr) perovskites for enhanced solar-driven hydrogen evolution and optoelectronic energy conversion

Abstract

Recent advances in photocatalytic technologies have highlighted the potential of perovskite materials, which have excellent optoelectronic properties and structural versatility. Furthermore, their photocatalytic efficacy can be markedly affected by the ambient pH conditions, which impact the alignment of their band edges with the redox potentials of water. This work employed density functional theory (DFT) computations to examine the optoelectronic and photocatalytic properties of XTiO 3 (X = Ca, Sr) perovskite materials in undoped, Te-monodoped, Zr-monodoped, and Te/Zr-codoped materials. The structural optimization showed negative formation energies for all compositions, indicating thermodynamic stability and suitability for application. Pure CaTiO 3 and SrTiO 3 have indirect band gaps, making them more active under UV light. In contrast, Zr-monodoped, Te-monodoped, and Zr/Te-codoped XTiO 3 systems have direct band gaps. Notably, the introduction of Te, either alone or in combination with Zr, causes a significant band-gap narrowing, allowing optical absorption in the visible light range. Furthermore, the computed band edge positions for Te-monodoped and Zr/Te-codoped XTiO 3 are well aligned with the redox potentials needed for overall water splitting, confirming their promising photocatalytic activity for hydrogen generation under visible light irradiation. However, under neutral pH conditions (pH = 7), only Te-monodoped and Zr/Te-codoped CaTiO 3 exhibit appropriate band edge alignments with the redox potentials of water, offering them promising candidates for solar-driven photocatalytic hydrogen production via overall water splitting. These findings indicate that Te-monodoped and Zr/Te-codoped XTiO 3 materials have considerable potential for renewable energy applications, such as solar-driven photocatalytic hydrogen generation, photovoltaics, and optoelectronics, due to their improved visible-light absorption. This paper establishes a robust theoretical framework for future experimental investigations. Photocatalytic mechanisms and band alignment of pure, doped, and co-doped XTiO 3 (X = Ca and Sr).