Breaking the O=O Bond: Deciphering the Role of Each Element in Highly Durable CoPd2Se2 toward Oxygen Reduction Reaction

In-depth insight into oxygen reduction reaction (ORR) electrocatalyst with high figures of merit (activity, stability, and selectivity) is highly crucial to rationally design electrocatalyst with a potential to replace state-of-the-art Pt/C. This work reports the synthesis of CoPd2Se2 nanoparticles that show remarkably high stability of 50000 electrochemical cycles toward ORR. Morphology of the particles is characterized using SEM and TEM microscopy techniques and simulated using Bravais-Friedel-Donay-Harker (BFDH) morphology calculation method. A deconvoluted approach was used to understand the role of each element in the compound. DFT calculation was performed to have an in-depth analysis of the active site. Co and Pd provided an active site for the O-2 adsorption and Pd dissociates the O=O bond. The back-donation of substantial electron density to the pi* antibonding orbital of the molecule expedites the 4e- reduction of O-2 throughout the entire potential range. During the electrochemical stability test, Se forms a protective layer and prevents the active Co and Pd sites from OH poisoning.