Synthesis and characterization of Z-scheme In2S3/Ag2CrO4 composites with an enhanced visible-light photocatalytic performance

Abstract

The low photocatalytic performance of a single photocatalyst mainly originates from a fast recombination of photogenerated charge carriers. Rational design and construction of direct solid-state Z-scheme photocatalysts is an effective approach to improve the charge separation efficiency of photogenerated electron–hole pairs. In this study, a series of Z-scheme In₂S₃/Ag₂CrO₄ composite photocatalysts with a different content of In₂S₃ were synthesized using a facile chemical precipitation method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL) spectroscopy and photoelectrochemical measurements. The photocatalytic activity of the In₂S₃/Ag₂CrO₄ composites was evaluated through photodegradation of methyl orange (MO) under visible light irradiation (λ > 420 nm). The results demonstrate that the optimal Z-scheme In₂S₃/Ag₂CrO₄ composite with a theoretical weight content of 4.0% In₂S₃ provided a photodegradation rate constant for MO of 0.0087 min⁻¹, which is approximately 2.8 and 5.4 times higher than those of pure In₂S₃ and Ag₂CrO₄, respectively. The enhanced photocatalytic activity may be attributed to the formation of a Z-scheme system between In₂S₃ and Ag₂CrO₄, effectively prolonging the lifetime of the photoinduced electrons generated by In₂S₃ and the photoinduced holes generated by Ag₂CrO₄, which was subsequently confirmed using active species trapping experiments, photoluminescence techniques and photoelectrochemical assays. This work may be useful for rationally designing new types of Z-scheme photocatalysts and provides some illuminating insights into the Z-scheme charge transfer mechanism for application in the solar energy conversion and environmental remediation fields.