General Method for Synthesis Transition-Metal Phosphide/Nitrogen and Phosphide Doped Carbon Materials with Yolk-Shell Structure for Oxygen Reduction Reaction

The transition metal phosphides have gradually emerged as promising electrocatalysts candidate for oxygen reduction reaction in recent years. As a research hotspot of transition metal phosphides, exploring their mechanism of catalytic activity and the influence of unique morphology is of great significance. In this study, a series of yolk-shell structure catalysts are fabricated only by pyrolyzing cyclophosphazene microspheres and metal salt without using any other templates, which M2P (M =Fe, Co, Ni) act as the core and N, P co-doped carbon as the shell. The yolk-shell structures aim to overcome the inferior conductivity and aggregation problems traditionally existed in application of transition metal phosphides through combination of transition metal phosphides and doped carbon materials. The prepared Fe2P/NPC, Co2P/NPC and Ni2P/NPC catalysts exhibit excellent ORR catalytic activity through the four-electron pathway, together with large electrochemically active surface area, superior stability and admiring methanol tolerance.