N, P, and S tri-doped holey carbon as an efficient electrocatalyst for oxygen reduction in whole pH range for fuel cell and zinc-air batteries

Abstract

Although, metal-free electrocatalysts have been exhibiting attractive oxygen reduction reaction (ORR) performance comparable to Pt/C in alkaline electrolytes, their activity in acidic and neutral mediums is unsatisfactory, hindering their widespread application in energy devices, such as proton exchange membrane fuel cells (PEMFCs), neutral metal-air batteries, and biofuel cells. Herein, N,P,S tri-doped holey carbon (NPS-HC) nanomaterials have been prepared using a one-step method with large specific surface area (1656.0 m2 g−1), abundant holes and edges, and high heteroatom content (7.57 at.%). The optimized NPS-HC exhibits outstanding ORR performance in universal pH mediums, being closely comparable to the commercial Pt/C. The NPS-HC is also utilized as air cathode in alkaline (peak power density: 286.6 mW cm−2 @ 488.1 mA cm−2) and neutral (85.7 mW cm−2 @ 228.8 mA cm−2) electrolytic Zn-air batteries as well as the ORR cathode in a practical PEMFC (275.1 mW cm−2) with comparable or superior performances than the previous reports. Such excellent electrocatalytic performance is attributed to the N,P,S tri-doping induced synergistic charge transfer and spin redistribution along with the hierarchical holey structure with exposed active sites and facilitated mass transport. Thus, this earth-abundant carbon-based nanomaterial holds great potential for high-performance pH-universal ORR catalysis in various energy-related technologies.