Sonophotocatalytic water splitting by BaTiO₃@SrTiO₃ core shell nanowires

Sonophotocatalysis has garnered significant attention due to its potential to enhance advanced oxidation processes, particularly water splitting, by employing materials with combined sonocatalytic and photocatalytic properties. In this study, we synthesized and investigated core-shell BaTiO₃@SrTiO₃ nanowires (BST NWs) with varying Sr/Ba molar ratios (2.5:7.5, 5.0:5.0, 7.5:2.5 mM, denoted as BST-1, BST-2, and BST-3, respectively) as catalysts for hydrogen production through water splitting. The piezoelectric nanowires demonstrated hydrogen evolution via both sonocatalysis and photocatalysis. In the sonophotocatalysis process, the ultrasonic vibration induced mechanical forces on the BST nanowires, thereby establishing a built-in electric field. This built-in electric field facilitated the effective separation of photo-generated charge carriers and prolonged their lifetimes, leading to a synergistic enhancement of hydrogen evolution. The pristine BaTiO₃ and SrTiO₃ nanowires exhibited relatively low hydrogen evolution rates (HER) of 7.0 and 6.0 µmol·g^-1min^-1, respectively. In contrast, the core-shell nanowires exhibited a substantial improvement in the hydrogen evolution rate. The HER increased with the addition of Sr, and BST-1, BST-2, and BST-3 achieved HERs of 12.0, 13.5, and 18.0 µmol·g^-1min^-1, respectively. The superior performance of BST-3 nanowires can be attributed to their highest piezoelectric potential and largest surface area. Additionally, BST-3 nanowires demonstrated remarkable stability over multiple cycles, validating their practical applicability as efficient photocatalysts.