Mn-N-P doped carbon spheres as an efficient oxygen reduction catalyst for high performance Zn-Air batteries

Low-cost and efficient oxygen reduction reaction (ORR) electrocatalysts are the key to developing Zn-air batteries for renewable energy storage. Herein, the Mn-N-P doped carbon sphere was prepared through polymerization of hexachlorotripolyphosphazene (HCCP) and phloroglucinol, and then followed the calcination at 900 °C. Theory calculations demonstrated the introduction of Mn in N-P doped carbon could lower the dissociation barrier of O₂ into O* and promote the ORR through a 4e⁻ pathway. The as-prepared catalysts exhibited a half-wave potential of 0.82 V vs. RHE and limiting current density of 5.2 mA/cm² toward ORR, which was comparable to those of the commercial Pt/C catalysts. In addition, Zn-air batteries with 0.05 Mn-N-P-C catalysts showed a high specific capacity of 830 mAh/g_Zn and excellent cycle stability. This facile approach demonstrated herein could be a solution to develop optimum non-precious metal catalysts for the application in cathodes of proton exchange membrane fuel cells. This study also provides new insight to design the catalysts of multi-heteroatom coordinated metal in the carbon matrix for both fundamental researches and practical applications.