MoS₂-mediated active hydrogen modulation to boost Fe²⁺ regeneration in solar-driven electro-Fenton process

The sluggish kinetics of Fe²⁺ regeneration seriously hinders the performance of Fenton process. However, the conventional Fenton system excessively stifle hydrogen-producing reactions, ignoring the significance of active hydrogen (H*) in Fe³⁺ reduction. Herein, a strategy of H* modulation is developed by decorating molybdenum disulfide (MoS₂) on a graphite felt (GF) cathode to boost Fe²⁺ regeneration in solar-driven electro-Fenton (SEF) process. With MoS₂ regulation, moderately dispersed MoS₂ on GF can serve as a bifunctional cathode, where the H* and hydrogen peroxide (H₂O₂) are simultaneously generated through H⁺ reduction and O₂ reduction, respectively. The in-situ generated H₂O₂ can trigger Fenton reactions with Fe²⁺, while the H* with robust reducing potential can significantly expedite Fe³⁺ reduction, consequently enhancing the HO• production. Both DFT calculations and EPR experiments confirm that H* can be activated via MoS₂ decoration. The results show that Fe²⁺ concentration in the MoS₂ @GF-SEF system remains at 15.74 mg/L (56.21%) after 6 h, which is 17.89 times that of the GF-SEF system. Moreover, the HO• content and organics degradation rate in the MoS₂ @GF-SEF are 3.61 and 5.30 times those of the GF-SEF, respectively. This study provides a practical cathode strategy of H* modulation to enhance HO• production and electro-Fenton process. ENVIRONMENTAL IMPLICATION: Boosting Fe²⁺ regeneration is of great value for the Electro-Fenton process. Herein, report a strategy to achieve this goal based on a MoS₂ @GF cathode. Remarkably, the MoS₂ @GF system exhibits exceptional efficiency for both various refractory organic compounds with environmentally hazardous effects and sterilization aspects, which can also work over a wide range of pH values (3-11). Specially, this system is driven only by solar energy. These characteristics make the electro-Fenton system more suitable for practical wastewater treatment.