Visible-light-driven reduction of hexavalent chromium ions by CdS/CaCO3 semiconductor–insulator photocatalytic heterojunction

To expand the range of application of insulating calcium carbonate (CaCO 3 ), we combined CaCO 3 with narrow bandgap cadmium sulfide (CdS) with the chemical precipitation method and characterized the composite through X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The photocatalytic activities of composite catalysts with different molar ratios on Cr 6+ are further investigated and compared. The materials showed good photocatalytic reduction effect on Cr 6+ under visible light. At the same time, the catalysts have good catalytic performance and service life, far exceeding pure CdS. The behavior of photogenerated carriers and free radicals in photocatalytic reduction processes were explored with a trapping agent experiment, and the mechanism that enhances catalytic activity in the CaCO 3 composite catalyst was revealed. Overall, results show that CaCO 3 has great potential as a photocatalyst.