Pt-non-precious transition metals (Pt-NPTMs) alloy electrocatalysts have gained considerable attention to develop cheaper and efficient electrocatalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs).

Graphite felt is a widely used electrode material for vanadium redox flow batteries. Electrode activation leads to the functionalization of the graphite surface with epoxy, OH, C=O, and COOH oxygenic groups and changes the carbon surface morphology and electronic structure, thereby improving the electrode's electroactivity relative to the untreated graphite. In this study, density functional theory (DFT) calculations are conducted to evaluate functionalization's contribution towards the positive half‐cell reaction of the vanadium redox flow battery. The DFT calculations show that oxygenic groups improve the graphite felt's affinity towards the VO2+/VO2+ redox couple in the following order: C=O>COOH>OH> basal plane. Projected density‐of‐states (PDOS) calculations show that these groups increase the electrode's sp3 hybridization in the same order, indicating that the increase in sp3 hybridization is responsible for the improved electroactivity, whereas the oxygenic groups’ presence is responsible for this sp3 increment. These insights can aid the selection of activation processes and optimization of their parameters.

In this study, we use density functional theory to investigate the catalytic activity of graphene (G), single vacancy defective graphene (G SV ), quaternary N-doped graphene (NG Q ), and pyridinic N-doped graphene (NG py , 3NG py , and 4NG py ) on Co(0001) substrate for an oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). The results show pyridinic N-doped graphene on a Co support exhibited better performance than the NG Q on a Co support and free-standing systems. According to the results, ORR intermediates (*OOH, *O, and *OH) become more stable due to the presence of a Co substrate. The single pyridinic (3NG py ) layer placed on Co(0001) is the most active site. The overpotential for Co/3NG py is rather higher compared to pure Pt( 111) catalyst (0.65 V). Therefore, pyridinic N-doped graphene with a cobalt support could be a promising strategy to enhance the ORR activity of N-doped graphene in PEMFCs.

Single-atom catalysts have been considered as potential candidates for fuel cell applications due to their good oxygen reduction reaction (ORR) activity. In this study, Co-N3S/C revealed a lower overpotential pathway for ORR activity in acidic solution in a fuel cell.