Probing Photo-excited Charge Carrier Trapping and Defect Formation in Synergistic Doping of SrTiO3

TL;DR

This study uses density functional theory to analyze how synergistic doping with Al and Ir in SrTiO3 affects defect formation, charge trapping, and photocatalytic efficiency, offering insights for improved water splitting catalysts.

Contribution

It provides a detailed theoretical investigation of how dual doping influences defect energetics and charge dynamics in SrTiO3 for enhanced photocatalytic performance.

Findings

Doping reduces charge trapping states in SrTiO3.

Synergistic Al and Ir doping modulates defect formation energy.

Optimal Ir:Al ratio improves photocatalytic efficiency.

Abstract

Strontium titanate (SrTiO3) is widely used as a promising photocatalyst due to its unique band edge alignment with respect to the oxidation and reduction potential corresponding to oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, further enhancement of the photocatalytic activity in this material could be envisaged through the effective control of oxygen vacancy states. This could substantially tune the photoexcited charge carrier trapping under the influence of elemental functionalization in SrTiO3, corresponding to the defect formation energy. The charge trapping states in SrTiO3 decrease through the substitutional doping in Ti sites with p-block elements like Aluminium (Al) with respect to the relative oxygen vacancies. With the help of electronic structure calculations based on density functional theory (DFT) formalism, we have explored the synergistic effect of doping with both Al and Iridium (Ir) in SrTiO3 from the perspective of defect formation energy, band edge alignment and the corresponding charge carrier recombination probability to probe the photoexcited charge carrier trapping that primarily governs the photocatalytic water splitting process. We have also systematically investigated the ratio-effect of Ir:Al functionalization on the position of acceptor levels lying between Fermi and conduction band in oxygen deficient SrTiO3, which governs the charge carrier recombination and therefore the corresponding photocatalytic efficiency.