Rational Synthesis of a Dual Z-Scheme CdS/Ag2MoO4/β-Bi2O3 Heterojunction for the Deep Photodegradation of Methylene Blue and Analysis of Its Mechanisms

In this work, a novel dual Z-scheme CdS/Ag2MoO4/β-Bi2O3 (CAB) composite heterojunction was synthesized, with the ultrafine CdS nanoparticles decorating two different-sized particles. In the beginning, the synergistic effect between BO and AMO makes the 10% Ag2MoO4/β-Bi2O3 (10AB) photocatalyst exhibit an optimal degradation efficiency of 87.1% for methylene blue (MB) of 10 mg·L−1 within 60 min; furthermore, its photocatalytic activity was enhanced by incorporating CdS nanoparticles on the surface of the AB heterojunction. The results showed that the 25% CdS/10% AMO/BO (25C10AB) composite achieved a maximum MB degradation efficiency of 99%. Optical and photoluminescence measurements showed that the dual Z-scheme CAB heterojunction has high crystallinity and efficient charge carrier migration and separation, which makes the samples more efficient for removing pollutants. Theoretical studies (DFT/FEM calculations) were performed to better understand the migration direction of e− and h+ in the photocatalytic degradation mechanism. This work provides a feasible approach to obtaining an efficient heterojunction composite photodegradation catalyst.