Piezophotodegradation and piezophotoelectrochemical water splitting of hydrothermally grown BiFeO3 films with various morphologies

This paper reports the use of the hydrothermal method in the fabrication of pure BiFeO3 (BFO) films with various morphologies [microparticle (BFOMP), microplate (BFOMPL), and microsheet (BFOMS)] on fluorine-doped tin oxide substrates and their applications in piezophotodegradation and piezophotoelectrochemical water splitting. These samples exhibited p-type characteristics, band gaps of approximately 2.1 eV, and favorable crystal. Piezoresponse force microscopy revealed that the piezoelectric coefficients of BFOMP, BFOMPL, and BFOMS were 13.0, 18.6, and 15.3 pm V−1, respectively. The associated piezotronic and piezophototronic characteristics of the samples were verified through facile current–voltage measurement, which revealed that BFOMPL outperformed BFOMP and BFOMS. Electrochemical and photoluminescence (PL) analyses demonstrated that BFOMPL possessed the highest electrochemical surface area per-unit mass (22.6 mF cm−2 mg−1) and the weakest PL emission. The combination of these characteristics and the favorable energy band positions under stress of BFOMPL contributed to its excellent piezophotocatalytic performance, with a piezophotodegradation rate constant of approximately 19.8 × 10–3 min−1 for methylene blue solutions, a piezophotoelectrochemical current density of approximately − 0.83 mA·cm−2 at −0.6 V (vs. Ag/AgCl) and a maximum piezo-induced applied bias photon-to-current conversion efficiency of 0.54% at −0.51 V. Based on the enhanced piezoelectricity, which can effectively enhance the separation of photogenerated electron-hole pairs, thus improving photocatalyst performance. BFOMPL also exhibited good reusability and versatility toward degrading different organic pollutants. The results indicate that our samples are promising for application in environmental sustainability.