In situ exsolved Co components on wood ear-derived porous carbon for catalyzing oxygen reduction over a wide pH range

Carbon-based catalysts with transition metal active sites hold great promise for electrochemically catalyzing the oxygen reduction reaction (ORR). However, it is still challenging to fabricate carbon catalysts containing transition metal active sites, which possess excellent and pH-universal capabilities of catalyzing the ORR, in a cost-effective and facile way. Here, using naturally abundant wood ear as a precursor, we demonstrate that carbon-based catalysts with Co components, named Co-C catalysts, can be prepared by an impregnation-precarbonization-activation strategy. We find that the obtained catalysts possess multiple catalytically active sites, including N heteroatoms, intrinsic defects, integrated Co nanoparticles, and well dispersed CoNx structures. The unique features endow our Co-C catalysts with a pH-universal catalytic capability, enabling them to effectively catalyze the ORR over a wide pH range. In an alkaline electrolyte, the performance of our optimum Co-C catalyst can compete with that of the benchmark Pt/C catalyst. Particularly, our optimum Co-C catalyst can outperform the Pt/C catalyst when applied in both alkaline and neutral Zn-air fuel cells. Based on our investigations, the incorporated Co nanoparticles should play a significant role in boosting the catalysis of the ORR in an alkaline electrolyte, while the CoNx structures in the matrix can contribute to improve the oxygen reduction performance in a neutral electrolyte. These results may open up a simple way to fabricate noble metal-free electrocatalysts from biomaterials and provide insights into the rational design of ORR catalysts for applications in practical fuel cells.