Enhanced Piezocatalytic Activity in Bi_1/2Na_1/2TiO₃ for Water Splitting by Oxygen Vacancy Engineering

Piezoelectric materials have demonstrated applicability in clean energy production and environmental wastewater remediation through their ability to initiate a number of catalytic reactions. In this study, we used a conventional sol-gel method to synthesize lead-free rhombohedral R3c bismuth sodium titanate (BNT) particles of various sizes. When used as a piezocatalyst to generate H₂ through water splitting, the BNT samples provided high production rates (up to 506.70 μmol g^-1 h^-1). These piezocatalysts also degraded the organic pollutant methylene blue (MB, 20 mg L^-1) with high efficiency (up to k = 0.039 min^-1), suggesting their potential to treat polluted water. Finally, we found that the piezopotential caused band tilting in the semiconductor and aided charge transfer such that recombination was suppressed and the rate of H₂ production increased. The mechanism of piezoelectric catalysis involved oxygen vacancies, the size of the catalyst, and the internal electric field playing important roles to enhance electron-hole separation, which further enhanced the catalysis reactions.