In situ growth of sulfide/g-C₃N₄ nano-heterostructures with an adjusted band gap toward enhanced visible photocatalysis

In this study, the nano-heterostructures of Zn_1−xCd_xS (0 < x < 1) nanoparticles and small g-C₃N₄ nanosheets (Zn_1−xCd_xS/CN) were prepared via in situ growth. Bulk g-C₃N₄ was first delaminated into thin layers by an acid and alkali assisted ultrasound method. Zn_1−xCd_xS nanoparticles were deposited on the surface of small g-C₃N₄ nanosheets in situ to fabricate Zn_1−xCd_xS/CN photocatalysts. The absorption band edges of the as-prepared Zn_1−xCd_xS/CN composites shifted to a longer wavelength region compared to g-C₃N₄. The Zn_1−xCd_xS/CN heterojunctions revealed super-enhanced visible-light photocatalytic activities compared to pure g-C₃N₄ and Zn_1−xCd_xS nanoparticles. To investigate the composition dependence, the mass ratios of Zn_1−xCd_xS and g-C₃N₄ were adjusted. Zn_0.8Cd_0.2S nanoparticles (5 wt%) grown in situ on g-C₃N₄ nanosheets as sample 5-Zn_0.8Cd_0.2S/CN revealed a very high photocatalytic activity compared to other Zn_0.8Cd_0.2S/CN and CdS/CN samples where the degradation of RhB was up to 99% within 15 min under visible light irradiation. This was ascribed to the well-matched band gap structure, large specific surface area and intimately contacted interfaces. The controllable band gap of the Zn_1−xCd_xS/CN composites was a key factor for their enhanced photocatalytic performance. In addition, O₂⁻ was the leading reactive oxidative species in this photocatalytic process in the 5-Zn_0.8Cd_0.2S/CN composite system.