Designing a Hierarchical Porous Carbon with Optimized Nitrogen Doping for Efficient Oxygen Reduction Reaction.

Abstract

Nitrogen-doped carbon is considered one of the most promising oxygen reduction catalysts due to its low cost and high activity, however, it still falls short of Pt/C. In this study, we report a strategy for the preparation of highly reactive N-doped hierarchical porous carbon by primary pyrolysis using zinc acetate as a stand-alone zinc source and amino-rich reactants as carbon and nitrogen sources to introduce Zn-Nx structures into mesoporous structures generated by the hard template method using the strong coordination of zinc and amino groups. Benefited from the simultaneous optimization of the hierarchical porous structure and nitrogen-doping, the half-wave potential of Zn(OAc)2-DCD/HPC is as high as 0.909 V vs. RHE, much better than that of commercial Pt/C catalysts (0.872 V vs. RHE). In addition, zinc-air batteries assembled with Zn(OAc)2-DCD/HPC (Pmax=198 mW cm-2) as the cathode exhibit higher peak power density compared to Pt/C (Pmax=168 mW cm-2). This strategy might open up new opportunities for designing and developing highly active metal-free catalysts.