Facet-dependent CdS/Bi4TaO8Cl Z-scheme heterojunction for enhanced photocatalytic tetracycline hydrochloride degradation and the carrier separation mechanism study via single-particle spectroscopy

Abstract

The charge separation efficiency is a pivotal factor for photocatalytic progress. Herein, an innovative approach was used to construct a novel CdS/Bi₄TaO₈Cl Z-scheme photocatalyst. To ensure the transmission of the carriers following the route of the Z-scheme, a facet engineering strategy and facet-dependent heterojunction design were performed for the synthesis of the catalyst. The CdS nanoparticles were primarily grown on the photoelectron-rich facets of the Bi₄TaO₈Cl to get a facet-dependent heterojunction structure. The results of the single-particle PL technique confirmed the carrier recombination sites of the Bi₄TaO₈Cl nanoplates and illustrated the necessity of the facet-dependent heterojunction design in the Z-scheme route. Finally, a built-in electric field derived from the facet heterojunction and the Z-scheme bandgap structure was formed and endowed the facet-dependent CdS/Bi₄TaO₈Cl Z photocatalyst with higher surface charge separation efficiency and better activity than the ordinary CdS/Bi₄TaO₈Cl heterojunction photocatalyst. The final degradation ratio of the optimized CdS/Bi₄TaO₈Cl was 81.1% in 80 min, and the calculated rate constant was 0.079 L mg⁻¹ min⁻¹, which is nearly 7 times that of the pristine Bi₄TaO₈Cl (0.011 L mg⁻¹ min⁻¹). Intermediate product analysis can prove the strong oxidation ability of the CdS/Bi₄TaO₈Cl photocatalyst. The results presented and the design concept will provide new ideas for the mechanism study of charge separation in composite catalysts.