Transition metal (Fe, Co, Ni) and sulfur codoped nitrogen-enriched hydrothermal carbon as high-performance cathode catalyst for microbial fuel cell

Microbial fuel cell (MFC), a new technology, uses microorganisms to decompose and oxidize the organic matter for bioelectricity generation. However, the sluggish oxygen reduction reaction of cathode catalyst is an important factor that affects electricity generation. Herein, nitrogen-enriched hydrothermal carbon doped with transition metal and sulfur heteroatoms was prepared. Carbon doped with iron, cobalt and nickel metal particles and nitrogen and sulfur heteroatoms (Fe-NSC, Co-NSC, Ni-NSC) exhibited maximum power densities of 2068 ± 32 mW m −2 , 1736 ± 49 mW m −2 and 1441 ± 45 mW m −2 , respectively. By analyzing the content and bonding configuration of nitrogen, sulfur, iron, cobalt and nickel, it is further verified that pyridinic nitrogen and graphitic nitrogen can reduce the charge transfer resistance, and iron–nitrogen (Fe–N) bonding and cobalt–nitrogen (Co–N) bonding are considered to be active sites which are beneficial to enhance oxygen reduction activity, while nickel–nitrogen (Ni–N) bonding is insensitive to oxygen reduction activity. Consequently, Fe-NSC is an effective catalyst for oxygen reduction reaction in MFC. • N, S and transition metal (Fe, Co, Ni) co-doped carbon is synthesized. • The maximum power density of Fe-NSC is 2068 ± 32 mW m −2 . • Fe, Co nanoparticles provide more effective active sites than Ni nanoparticles. • Fe-NSC and Co-NSC are four-electron ORR processes.