Synergistic coupling ensuing cobalt phosphosulfide encapsulated by heteroatom-doped two-dimensional graphene shell as an excellent catalyst for oxygen electroreduction

We synthesized cobalt phosphosulfide (CPS) encapsulated in heteroatom-doped (N, S, P) graphene (CPS@GN,S,P) to achieve highly synergistic and durable catalyst for the oxygen reduction reaction (ORR). The catalyst was precisely tuned using Co metal (M) and suitably integrated with P and S by a simple method of thioureaphosphate-assistance, followed by reductive annealing at 700 degrees C. The possible P-S interactions simultaneously altered the cobalt phosphide crystallinity and improved the defective CPS nanocrystal's interface in the CPS@GN, S,P catalyst. Theoretical investigation demonstrated that doping can induce imbalanced charge distortion on the graphene network and yield thermodynamically-favorable O2 adsorption and dissociation. The nonstoichiometric CPS nanoparticles with M-P-S unit that had been appropriately phase-engineered by controlling the Co3+/Co2+ couple activation with effective electronic structure tuned, could enhance the multiple oxygen-adsorption electroactive sites for catalyzation. Such integrated catalyst can yield an efficiently synergistic ORR with high mass/charge transfer, excellent methanol stability and durability comparable to commercial Pt/C in alkaline medium. CPS@GN,S,P is a promising alternative to Pt as a catalyst for ORR in fuel cells and metal-air batteries.