Systematically theoretical investigation the effect of nitrogen and iron-doped graphdiyne on the oxygen reduction reaction mechanism in proton exchange membrane fuel cells

Developing economical electrocatalysts as alternatives to platinum for oxygen reduction reaction (ORR) to develop the applications of green energy devices like proton exchange membrane fuel cells (PEMFCs) is of paramount importance. In the current study, a different ratio of nitrogen-doped graphdiyne (GDY) with Fe single-site is reported to be more cost-effective and efficient for PEMFCs. The current study also demonstrates the design principle to improve the ORR activity associated with catalysts using Fe single-site with a greater Fe charge, which is controlled through the coordinated structure of the active center. Based on the simulation results, the formation of N2-doped GDY and N2-doepd Fe-GDY are more lucrative compared to the formation of Nx-doped GDY (x > 2) in terms of energy. O2 molecules have a direct dissociation on the N2-doepd Fe-GDY via Eley-Rideal (ER) mechanism, which involves the formation of H2O by reacting with H+ from the electrolyte. Moreover, N2-doepd Fe-GDY exhibits better performance as an ORR catalyst in an acidic medium because of its low overpotential of 0.488 V. However, N2-doped GDY follows the OOH∗ formation pathway, showing a higher overpotential for ORR. Furthermore, in the structure under study, the thermodynamic favorability of ORR is observed since the reaction energies calculated at each reaction step are exothermic and the energy profile of all reaction steps are downhill. The results of the current work provide new insights into the construction of extremely efficient heterogeneous catalysts in electrochemical energy technologies.