Construction of a binary S-scheme S-g-C3N4/Co-ZF heterojunction with enhanced spatial charge separation for sunlight-driven photocatalytic performance

Abstract

A step-scheme (S-scheme) photocatalyst made of sulfurized graphitic carbon nitride/cobalt doped zinc ferrite (S-g-C₃N₄/Co-ZF) was constructed using a hydrothermal process because the building of S-scheme systems might increase the lifespan of highly reactive charge carriers. Utilizing cutting-edge methods, the hybrid photocatalyst was evaluated by employing TEM, XPS, XRD, BET, FTIR, transient photo-response, UV-vis, EIS and ESR signals. In order to create a variety of binary nanocomposites (NCs), nanoparticles (NPs) of 6% cobalt doped zinc ferrite (Co-ZF) were mixed with S-g-C₃N₄ at various concentrations, ranging from 10 to 80 wt%. For photocatalytic dye removal, a particular binary NC constructed between S-g-C₃N₄ and Co-ZF produces a huge amount of catalytic active sites. The findings showed that loading of S-g-C₃N₄ on 6% Co-ZF NPs serves as a good heterointerface for e^-/h⁺ separation and transportation through the S-scheme S-g-C₃N₄/Co-ZF heterojunction. By boosting the hybrid system's BET surface area for the photocatalytic process, the addition of 6% Co-ZF improves the system's ability to absorb more sunlight and boosts its photocatalytic activity. The highest photo-removal effectiveness (98%), which is around 2.45 times higher than that of its competitors, was achieved by the hybrid photocatalyst system with an ideal loading of 48% Co-ZF. Furthermore, the trapping studies showed that the primary species involved in the MB aqueous photo-degradation were ˙OH^- and h⁺.

Fig. 1. XRD pattern of zinc ferrite, S-g-C₃N₄, 6% Co-ZF and 48% S-g-C₃N₄/6% Co-ZF.

Fig. 2. TEM images of (a) S-g-C₃N₄, (b) ZF, (c) 6% Co-ZF, and (d) 48% S-g-C₃N₄/6% Co-ZF.

Fig. 3. (a) FT-IR assessments, (b) ZF, S-g-C₃N₄, 6% Co-ZF, and 48% S-g-C₃N₄/6% Co-ZF NCs N₂ adsorption–desorption are used to compute the BET surface area isotherms, (c) UV-vis absorption ranges and (d) Tauc's plots of ZF, S-g-C₃N₄, 6% Co-ZF, and 48% S-g-C₃N₄/6% Co-ZF heterostructure.

Fig. 4. MB deterioration in visible light illumination measurements for (a) ZF, Co-ZF (2, 4, 6, 8 and 10%) NRs, and (b) 48% S-g-C₃N₄/6% Co-ZF. (c) MB's photodegradation rate and (d) dye kinetic pseudo-first-order graphs, 6% Co-ZF, ZF, and Co-ZF/S-g-C₃N₄ (12, 24, 48, 60 & 80 wt%) NCs.

Fig. 5. (a) Cyclic stability of a 48% S-g-C₃N₄/6% Co-ZF NCs photocatalyst for six subsequent experiments on MB photoremoval. (b) Transient photocurrent results of ZF, 6% Co-ZF, S-g-C₃N₄, and 48% S-g-C₃N₄/6% Co-ZF under visible-light irradiation (>420 nm). (c) EIS Nyquist plots of ZF, 6% Co-ZF, S-g-C₃N₄ and 48% S-g-C₃N₄/6% Co-ZF NCs. (d) Scavengers' impact on the 48% S-g-C₃N₄/6% Co-ZF NCs photocatalytic activity.

Fig. 6. Designing the reaction pathways for the photocatalytic elimination of MB using 48% S-g-C₃N₄/6% Co-ZF utilizing a feasible S-scheme heterojunction.