Unveiling of Interfacial Charge Carrier Dynamics in rGO Wrapped g-C3N4/SnO2 Heterostructure for Enhanced Adsorption and Sunlight-Driven Photocatalysis

This work demonstrates the engineering of an rGO-wrapped g-C₃N₄/SnO₂ ternary heterojunction-based photocatalyst via a one-step in situ hydrothermal technique. The well-positioned CB edge of g-C₃N₄ and the VB of SnO₂ create a type-II heterojunction, making g-C₃N₄/SnO₂ a promising photocatalyst for efficient redox reactions. Further, the incorporation of rGO, with its high specific surface area, significantly enhances the density of active site availability of the resulting ternary rGO/g-C₃N₄/SnO₂ heterostructure. The reduced band gap and formation of the multiple heterojunctions improve the separation and migration efficiency of photogenerated charge carriers, making the rGO/g-C₃N₄/SnO₂ heterojunction highly effective for removing a diverse category of pollutants. A small dose of 0.3 mg/mL of the ternary heterostructure degrades 99.3% of RhB dye under the exposure of simulated solar light for 40 min. Remarkably, the ternary heterostructure exhibits exceptional photodegradation efficiency for a mixture of dyes (MB + RhB + MO) with a high concentration of 30 mg/L, achieving removal rates of 99.99%, 71.4%, and 71%, respectively, within 40 min of irradiation. Moreover, first- and second-order in addition to the intraparticle diffusion models were used to determine the rate constants and equilibrium adsorption capacities of the rGO/g-C₃N₄/SnO₂ heterostructure, uncovering the underlying adsorption mechanisms. To comprehend the mechanistic intricacies underlying photocatalysis, a charge transfer process at the multiple interfaces has been thoroughly discussed using the experimentally determined values of work function and band edge positions from ultraviolet photoelectron spectroscopy and Mott–Schottky analysis, respectively. Eventually, the scavenger’s study affirms that the photogenerated e^––h⁺ pairs, superoxide anion, and hydroxyl free radicals all play an active role in the photodegradation process.