Enhanced efficiency of methyl orange degradation by S-doped molybdenum carbide in an electrochemical system: experiment and DFT calculation

This study developed a S-doped two-dimensional molybdenum carbide composited with graphene oxide (S-Mo x C/GO) for efficient electrochemical degradation of methyl orange (MO). The incorporation of S refined the MoₓC nanocrystals and reduced graphene stacking, significantly enhancing electrocatalytic performance. The S- Mo x C /GO system achieved 99.9% removal of 10 mg/L MO within 45 min, outperforming the undoped counterpart (95.2%). Quenching tests identified singlet oxygen ( 1 O 2 ) as the dominant reactive species. DFT calculations revealed that S doping facilitates H 2 O adsorption and promotes electron transfer from H 2 O to adjacent Mo sites, thereby accelerating the activation of oxygen species for 1 O 2 generation. Degradation pathways were proposed based on HPLC and computational analysis. Additionally, toxicological assessment indicated that most degradation products exhibit low ecological risk. This work elucidates the role of S doping in enhancing catalytic activity and provides a feasible strategy for designing efficient Mo x C-based catalysts for organic wastewater treatment.