N, P-co doped carbon nanotubes coupled with Co2P nanoparticles as bifunctional oxygen electrocatalyst

Abstract Employing P-doped polypyrrole nanotubes as precursor, we have constructed a structure of N, P-codoped carbon nanotubes coupled with Co2P nanoparticles (Co2P/NPC). Herein, P element serves as a bridging agent enabling strong electronic coupling between NPC and Co2P. While Co2P with good electrical conductivity facilitates electron transfer during electrocatalytic process. As a result, Co2P/NPC can catalyze oxygen reduction reaction (ORR) in a direct 4e− pathway, reaching a half-wave potential of 0.835 V vs. RHE and a smaller Tafel slope of 45.9 mV dec−1 than commercially available Pt/C. On the other hand, Co2P/NPC can also catalyze oxygen evolution reaction (OER) in a low overpotential of 320 mV at 10 mA cm−2 and a smaller Tafel slope of 59.6 mV dec−1 than commercially available RuO2. Finally, the potential application of Co2P/NPC catalyst is estimated in case of rechargeable Zn-air battery. As air electrode, Co2P/NPC achieves a power density of 154 mW cm−2 and good long-term cycling stability (over 90 h at 5 mA cm−2). Our work thus provides a facile strategy to achieve bifunctional ORR/OER performance for application in next-generation energy conversion systems.