Boosting of the piezoelectric photocatalytic performance of Bi2MoO6 by Fe3+ doping and construction S-scheme heterojunction using WO3

Abstract

Although self-polarized piezoelectric semiconductor photocatalysts significantly enhance the separation of internally generated photocarriers, their photocatalytic performance is constrained by insufficient internal polarisation and a wide bandgap. Additionally, the low concentration of oxygen in contaminated water limits the effectiveness of such photocatalysts. To the best of our knowledge, this study was the first to determine that the piezoelectric properties of Bi₂MoO₆ (BMO), was due to the polarisation displacement of the MoO₆ octahedron that occurred along the x-axis, as revealed through density functional theory (DFT) calculations. Subsequently, the self-polarisation characteristics of BMO were enhanced and the bandgap was reduced through Fe³⁺ doping, as confirmed via atomic force microscopy, hysteresis loop measurements and DFT analysis, resulting in an increase in surface potential from 30.41 to 46.80 mV. Furthermore, an S-scheme WO₃/Bi₂MoO₆:Fe³⁺ heterojunction was developed to improve the surface separation of photoelectron–hole pairs. The piezoelectric photocatalytic performance of this sample was evaluated through the degradation of rhodamine B (RhB) and oxygen generation. Results indicated that the degradation rate of RhB reached 98.63 % within 25 min under the synergistic influence of light and ultrasound, which was 1.85 and 9.60 times higher than those of Bi₂MoO₆ and WO₃, respectively. Furthermore, the optimal oxygen production efficiency was 167.41 µmol·g⁻¹·h⁻¹. This study provides a novel approach for designing more efficient piezoelectric photocatalysts.