Sponge-like N-doped carbon materials with Co-based nanoparticles derived from biomass as highly efficient electrocatalysts for the oxygen reduction reaction in alkaline media

The development of highly efficient and low-cost catalysts towards Oxygen Reduction Reaction (ORR) is of significance for renewable energy technologies such as proton-exchange membrane fuel cells and metal-air batteries. This study is to utilize the biomass of soybean straw as the supporting carbon materials to prepare nitrogen and cobalt dual-doped porous biocarbon electrocatalysts (CoNASS) possessing high content of N (1.92%), embedding cobalt nanoparticles and sponge-like structure with high specific surface area (1185.00 m² g^-1) as well as appropriate pore diameter (∼2.17 nm). Meantime, CoNASS exhibits a good electrocatalytic activity with a half-wave potential of 0.786 V (vs. RHE), comparable to a half-wave potential of 0.827 V (vs. RHE) for the commercial Pt/C. The detections of electrochemical kinetics show the electron transfer number of CoNASS is in the range of 3.84-3.92, which indicates 4-electron pathway dominantly occurs in ORR. And the limiting diffusion current density of CoNASS at 1600 rpm is around 5.8 mA cm^-2 slightly higher than that of the benchmark Pt/C (5.6 mA cm^-2). This work opens a new avenue to utilize soybean straw, one of agriculture waste of large quantity, to prepare high efficient and low-cost catalysts for ORR.