Fenton-like photocatalytic oxidation and adsorption performance of MXene/g-C3N4 heterostructures under H2O2 oxidizer: experimental & modeling approach

The rapid growth of textile industry has negatively impacted the health and quality of clean water sources, leading to an increase in water pollution disaster. To address these significant water effluent issues, there is a strong need for improved and effective environmental remediation processes to treat effluents containing organic contaminants. The present research explores the photocatalytic and adsorption capabilities of MXene/g-C3N4 for the discoloration of methylene blue (MB) by introducing a strong oxidizing agent, such as hydrogen peroxide (H2O2). To the best of our knowledge, this study is the first one to demonstrate that the MXene/g-C3N4 photocatalyst could efficiently activate H2O2, reducing the MB concentration by up to 99.71% and 81.88% in 240 min via photocatalysis and adsorption processes, respectively. The addition of H2O2 oxidant in photocatalysis system rapidly reduced the recombination rate of photogenerated electrons-hole pairs by producing powerful hydroxyl and superoxide radicals in the Fenton-like oxidation process. Langmuir–Hinshelwood kinetic modeling excellently described the degradation of MB, showing the highest R2 value of up to 0.9896. The thermodynamic parameters, including Gibbs free energy (ΔG° = − 28.203 to − 30.095 kJ/mol), entropy (ΔS° = 94.558 kJ/mol K, enthalpy (ΔH° = 25.255 kJ/mol and activation energy (Ea = 11.066 kJ/mol), confirmed that the system is spontaneous and favorable for MB degradation. The reduction in ΔG° contributed to the expansion of photocatalyst’s pores, while the positive value ΔS° at higher temperatures indicated an increase in the kinetic energy of the degradation system, encouraging a higher rate of diffusion of methylene blue towards MXene/g-C3N4. In adsorption modeling, the adsorption of MB followed intraparticle diffusion kinetics and Temkin isotherms, with the highest R2 values of 0.9906 & 0.9965, respectively. A series of MXene/g-C3N4 heterostructure photocatalysts (1, 4, 8 and 12 wt. %) was synthesized via a wet impregnation method and characterized through TEM and FESEM characterizations. This work provides new insights into the application of MXene/g-C3N4 for the improvement of photocatalysis system by introducing a powerful oxidizer.