Synergistic effects of a dual p-n heterojunction in a Co₃O₄-Ag₂O-SrTiO₃ ternary composite for enhancing photocatalytic degradation of toluene

The construction of multi-coupled heterojunction materials has garnered significant research interest for environmental remediation. In this study, a ternary double p-n heterojunction Co₃O₄-Ag₂O-SrTiO₃ (Co₃O₄-Ag₂O-STO) was prepared by introducing Co₃O₄ into Ag₂O-STO, which was synthesized by chemical precipitation and then subjected to a photo-deposition method, and was used for the photocatalytic degradation of toluene. The photocatalytic activity of the ternary composite material in degrading toluene under full light illumination was evaluated, and the reaction rate of Co₃O₄-Ag₂O-STO was 40.18 nmol g⁻¹ s⁻¹, which is superior to those of pure STO (10.42 nmol g⁻¹ s⁻¹), Ag₂O-STO (34.72 nmol g⁻¹ s⁻¹), and Co₃O₄-STO (27.28 nmol g⁻¹ s⁻¹). Photoelectrochemical tests and fluorescence spectroscopy analysis indicated that the narrow band gaps of Ag₂O and Co₃O₄ increase the visible light response range of the ternary composite material, and the incorporation of Co₃O₄ provides more pathways for the transfer of photogenerated carriers, reducing the recombination rate of photogenerated electron-hole pairs. Furthermore, the formation of a ternary double p-n heterojunction transfers more holes to the Ag₂O and Co₃O₄ on the catalyst surface for reaction, providing more active sites. This research presents a promising approach for the fabrication of heterojunction photocatalysts for environmental remediation.