CdS/BaTiO3 Heterojunction Composite for Complete Visible Piezophotocatalytic NO Oxidation in Self-Cleaning and Air Purification

NO causes air pollution and promotes PM_2.5 and O₃ formation. However, the widespread presence of trace NO in air is difficult to remove using traditional technologies. This study developed a novel visible piezophotocatalyst composed of BaTiO₃ (BTO) and CdS, which exhibited high piezophotocatalytic activity for NO oxidation under wind blowing and sunlight irradiation, about 1.5 times greater than that of pristine CdS. Moreover, it displayed almost absolute selectivity toward NO₃^-, thereby mitigating the risk of secondary pollution from nitrogen oxide intermediates. Notably, CdS/BTO also demonstrated excellent stability, maintaining consistent performance across more than six consecutive cycles. The high activity was attributed to the generation of surface charges and an internal electric field by the piezoelectric effect of the BTO under wind friction. The surface charges enhanced the adsorption and activation of NO molecules via electrostatic attraction, while an internal electric field promoted photocharge separation and thus suppressed photoelectron-hole recombination. Besides, the electrostatic attraction retarded the desorption of NO₂ and other intermediates, leading to the complete oxidation of NO to NO₃^-. Furthermore, the electrostatic attraction also enhanced the interaction of CdS/BTO with the substrate to inhibit leaching, even at very high wind speeds, and decreased the photocorrosion of CdS, leading to strong durability. This work provides deep insight into the piezophotocatalytic mechanism and supplies a feasible method for self-cleaning and air purification by decorating CdS/BTO onto a vehicle outer surface.