La,Al-Codoped SrTiO<sub>3</sub> as a Photocatalyst in Overall Water Splitting: Significant Surface Engineering Effects on Defect Engineering
Yalei Qin, Fan Fang, Zhengzheng Xie, Huiwen Lin, Kai Zhang, Xu Yu, Kun Chang
Abstract
Suppressing the formation of defects such as oxygen vacancies and Ti3+ in SrTiO3 perovskite lattice has been regarded as an effective way to improve photocatalytic performance in overall water-splitting reaction. In this work, a series of La,Al-codoped SrTiO3 catalysts are synthesized by a flux treatment method after grounding. An appropriate doping amount of La3+ and Al3+ ions into perovskite will lead to fewer defects, responsible for enhancing photocatalytic performance. Al3+ ion doping will introduce the oxygen vacancies into the perovskite, resulting in a decreasing number of Ti3+ ions. During the defect engineering, more Sr2+ will precipitate onto the perovskite surface caused by the introduction of Al3+. Hence, surface engineering is applied through appropriate La3+ ion doping contributing to the lattice distortion, allowing surficial Sr2+ to re-enter the perovskite lattice, leading to the promoted conversion of Ti3+ to Ti4+. Simultaneously, the La3+ ion doping is also beneficial to the decrease in oxygen vacancies. As a result, the essential relationship between the La3+ doping amount and photocatalytic performance in overall water splitting is revealed. The optimized 0.6% La and 1% Al codoped SrTiO3 sample loading Rh (0.1 wt %)/Cr2O3 (0.05 wt %)/CoOOH (0.05 wt %) gives the highest activity and good stability, with gas evolution rates of 1.79 mmol·h–1 (H2) and 0.91 mmol·h–1 (O2). In comparison, the apparent quantum efficiency is 78.43% under 365 nm irradiation.