Co-Loaded N-Doped Biochar as a High-Performance Oxygen Reduction Reaction Electrocatalyst by Combined Pyrolysis of Biomass

In this study, a Co-loaded N-doped biochar electrocatalyst (Co@NCBC) was prepared from biomass waste (sawdust) using a new combined pyrolysis method. The carbon support of Co@NCBC derived from the first step (low-temperature carbonization) contained abundant active oxygen-containing functional groups and could facilitate nitrogen introduction and Co-based nanoparticle dispersion in the second step (high-temperature pyrolysis) under a NH3 atmosphere. The Co@NCBC exhibited excellent oxygen reduction reaction (ORR) activity with a half-wave potential E1/2 of 0.860 V vs a reversible hydrogen electrode, which could be comparable to commercial 20 wt % Pt/C. Furthermore, Co@NCBC exhibited higher stability (the current remained 98.1% after running for 10 000 s) and methanol tolerance (the current remained 96.5% after adding methanol) than Pt/C. The superior ORR activity of Co@NCBC was mainly attributed to the high content of graphitic-N and pyridinic-N/N–Co doping, developed pore structure, and good dispersion of Co-based nanoparticles. This study proposes a preparation approach of low-cost ORR electrocatalysts using non-noble metals and sustainable biomass.