Fabricating efficient SnO2/hydrochar heterojunction visible light photocatalyst for Cr(VI) reduction

Despite its low cost, environmental friendliness and excellent stability, SnO2 exhibits no visible light photocatalytic activity due to its wide bandgap. This study aims to develop an efficient visible light photocatalyst by combining SnO2 with hydrochar (HC). A series of SnO2/HC nanocomposites were synthesized using a green one-pot hydrothermal method, by changing the amount of glucose. SnO2/HC-3 exhibited the maximal photocatalytic Cr(VI) reduction rate (0.030 min(-1)), which is 30 times higher than SnO2 and 5 times higher than HC under visible light (lambda > 420 nm) irradiation. Moreover, when the photocatalytic experiment conditions were optimized, SnO2/HC-3 showcased the further improved photocatalytic performance for Cr(VI) reduction. SnO2/HC-3 also remained good photocatalysis capability for Cr(VI) reduction after four cycles, and demonstrated remarkable photochemical stability. The mechanism for the superior visible light photocatalysis of SnO2/HC-3 was explored and proposed. Furthermore, SnO2/HC-3 showcased a high efficiency toward photocatalytic removal of Cr(VI) in the diluted passivation solution of copper alloys under visible light, indicating that SnO2/HC-3 has an application prospect in practical Cr(VI)-containing wastewater treatment.