Nitrogen/Phosphorus/Boron-Codoped Hollow Carbon Spheres as Highly Efficient Electrocatalysts for Zn–Air Batteries
Yuebing Wang, Aling Chen, Can Fang, Qingfeng Yi
Abstract
Considering the shortage of platinum resources and its high price, it is crucial to explore its substitutes to satisfy the market demand of metal–air batteries. Thence, N/P/B-codoped hollow carbon nanospheres were synthesized by doping B and P into polydopamine spheres. Thanks to the abundance of defects in the hollow carbon sphere shell, the large active area, the high content of pyrrolic N, and B–C, C–N, and other electrocatalytic active sites, NHCS@B1P2 exhibits excellent oxygen reduction reaction (ORR) catalytic performance. Electrochemical tests show that NHCS@B1P2 has outstanding ORR electroactivity in alkaline electrolytes, with a half-wave potential (E1/2) 60 mV higher than Pt/C and a limiting diffusion current density 0.97 mA cm–2 greater than Pt/C. Meanwhile, NHCS@B1P2 (E1/2 = 0.86 V) still exhibits superior electrochemical performance to Pt/C in neutral media. It is noteworthy that a Zn–air battery (ZAB) using NHCS@B1P2 as the ORR catalyst exhibits a higher peak power density (158.5 mW cm–2 for an alkaline ZAB and 104.6 mW cm–2 for a neutral ZAB) than Pt/C (136/46.7 mW cm–2) in both alkaline and neutral electrolytes. In step discharge at different current densities, it still has a stable voltage value comparable to (even higher than) Pt/C. In addition, NHCS@B1P2 exhibits a more durable and stable voltage plateau than Pt/C at 10 mA cm–2. This work provides a practical and valuable avenue for the application of heteroatom-doped carbon-based ORR catalysts in ZABs.