Iron/cobalt-decorated nitrogen-rich 3D layer-stacked porous biochar as high-performance oxygen reduction air-cathode catalyst in microbial fuel cell

Developing low-cost and high-efficiency oxygen reduction reaction (ORR) catalysts is crucial to the commercial application of microbial fuel cell (MFC). Herein, Fe/Co-decorated nitrogen-rich three-dimensional (3D) layer-stacked porous biochar (Fe/Co-NC-x) have been synthesized from silk gel through secondary carbonization of activated carbons which firstly adsorbed metal ions. The multilayer porous structure of Fe/Co-NC-3 contributes to construction of high specific surface area (576 m2 g-1), large pore volume (1.27 cm3 g-1) and many defect structure (ID/IG = 1.004). As expected, with Fe/Co synergistic effect, Fe/Co-NC-3 exhibits excellent ORR performance through 4e- pathway with good methanol resistance. In addition, the performance of MFC using Fe/Co-NC-3 as air-cathode catalyst is more prominent with higher maximum power density (1059.62 ± 30.00 mW m-2) compared to that using NC (668.19 ± 9.84 mW m-2) and commercial Pt/C catalyst (957.33 ± 10.50 mW m-2). Therefore, Fe/Co-NC-3 should be a prospective catalyst in the practical application of fuel cells and other energy devices.