Efficient electro-Fenton-like degradation of para-nitroaniline via synergistic MIL-53(Fe,Cr)MOF/NGO heterogeneous catalysts.

The utilization of metal-organic frameworks (MOFs) for the removal of pollutants in water has sparked heightened attention in recent research. This work explored in situ H2O2 generation by developing a MIL-53(Fe,Cr)/nitrogen-doped graphene oxide (NGO) electro-Fenton-like system to degrade p-nitroaniline (PNA). At optimal conditions of 10 wt% NGO and 90 wt% MIL-53(Fe,Cr), 98.68 % degradation efficacy was realized (initial PNA concentration = 10 mg/L), along with a kinetic constant of 0.38 min-1, surpassing earlier Fe/C micro-electrolysis and FeSO4.7H2O/H2O2 systems by 19 times and ∼5 times, respectively. Importantly, the superior behavior was strongly hinged on the synergistic effect of the Fe and Cr metal centers, amidst NGO, which increased the generation of oxygen vacancies vital for O2 adsorption, •O2- production and electron transport among Cr/Fe. Moreover, the avalanche of electrons supplied by the nitrogen-doped graphene oxide further promoted H2O2 formation. Quenching experiments indicated PNA removal rates of 96.77 %, 84.85 %, and 89.36 % in the presence of tert-butanol, p-benzoquinone, and tryptophan, highlighting the roles of •OH, •O2-, and 1O2 in the degradation mechanism. Additionally, the catalyst demonstrated 98.67 % degradation efficacy even after seven cycles. This study presents a straightforward method for synthesizing MOF cathodes, advancing our knowledge of creating effective electrodes through binary metal approaches.