Theoretical investigation of d-orbitals involvement in catalytic activity by incorporation of bimetallic on adjacent position

Numerous articles on M-N-C-based materials have been extensively studied for their catalytic activity in various reaction perspectives, such as CO oxidation, CO2 reduction, oxygen reduction, and oxygen/hydrogen evaluation. However, the understanding of the involvement of d-orbitals of transition metal atoms and the tunability of their electronic structure for different catalytic species is under observation. Herein we have suggested bimetallic iron doped nitrogen-based graphene FeN4-MN4/Gr (M= Co, Ni, Cu, Zn) and single-atom iron-doped nitrogen-based graphene for comparative study. The effect of bimetallic atoms on iron on the adjacent position was studied by Bader charge, adsorption energy for different species, and the strengthening of iron nitrogen codoped graphene Fe-N4/Gr. Moving from Co to Zn, the number of outermost electrons is increasing, creating steric hindrances effect and torsional strain, affecting Bader charge and formation energy and changing the bond length between nitrogen and iron. Similarly, steric hindrance also has a prominent effect on the d-orbital, as moving from Co to Zn, the availability of finding of d-orbital on z-direction are increasing which is confirmed by adsorption energy of different species like Co, O2, and H+ + e-. Our finding reveals that not only d-orbitals along the z-direction can play a vital role in catalytic activity, but the d-band center and magnetic moment also have a projecting role in boosting catalytic activity.