Coordination environment engineering of graphene-supported single/dual-Pd-site catalysts improves the electrocatalytic ORR activity

Coordination engineering is a promising strategy to improve the electrocatalytic ORR activity of single/dual-metal-site catalysts. In this work, the electrocatalytic processes of graphene-supported C, B and N coordination single/dual-Pd-site catalysts were investigated by systematic density functional theory (DFT) calculations, and compared with Pd(100). The results show that different coordination environments (C, B and N) can strongly affect the adsorption and reaction characteristics of O-2 and O-containing intermediates. The B coordination (PdB4/C and Pd2B6/C) catalysts are located in the left region of the volcano, removal of *OH is the potential determining step (PDS), while the C and N coordination (Pd2C6/C, PdN4/C and Pd2N6/C) catalysts are located in the right region, where the formation of *OOH is the PDS. In addition, Pd2B6/C catalyst greatly promote the cleavage of O-O bond, enabling the ORR to occur through both dissociative and associative mechanisms. Among all catalysts, Pd2B6/C stands out with a low overpotential of 0.48 V and shows good ORR performance. Therefore, it has great potential to replace Pt-based catalysts. Finally, the origin of ORR activity was revealed by analyzing the electronic structure and work function, which provided guidance for the design of effective ORR electrocatalyst.