Preparation of MnO/Mn₂O₃-doped carbon fibers as a cathode for electrochemical degradation of pharmaceutics

In electrochemical degradation processes such as electro-Fenton, the use of modified electrodes is a suitable method to improve cathode performance, reduce energy consumption, and simplify the system and its feasibility, all without adding any catalyst. In this research, graphite-felt (GF) fibers were coated with Mn-doped carbon as the active material, serving as electrode substrates. Contact angle, XRD, Raman, and SEM analyses confirmed the effective surface functionalization of GF fibers. The results of XPS, Raman, and EDS analyses showed that Mn was predominantly present as Mn₂O₃ in the final electrode structure and acts as the active material. LSV plots showed that the modification had reduced the onset potential and increased the current of the O₂ reduction peak. By modifying the surface, the cathode performance in the degradation of rifampin (RIF), as a model pollutant, was improved, enabling it to degrade more than 80% of the RIF in 30 min in the absence of any homogeneous or heterogeneous catalyst, with faster kinetics and lower energy consumption. Experiments showed that O₂ played a fundamental role as the main reactant and the resulting active species, ¹O₂, and O₂^•- have the significant roles, reducing the relevant degradation efficiency (DE%) to 5% and 16%, respectively in the scavenger experiments, while ^•OH had a considerably lesser impact (DE%=58%). Nine degradation intermediates were identified, and toxicity evaluation confirmed the progressive detoxification of the treated solution.