Cu2+-doped NiCo2O4 composite modified carbon felt cathode in marine sediment microbial fuel cells and its enhanced dissolved oxygen reduction reaction kinetics for higher power output

The development of efficient and stable non-precious metal cathodes is critical to the practical application of marine sediment microbial fuel cells (MSMFCs). Herein, a series of Cu²⁺-doped NiCo₂O₄ spinel cathodes were synthesized in-situ on carbon felt (CF) via a hydrothermal growth to enhance the dissolved oxygen reduction reaction (DORR) in seawater. The optimal electrode (CNCO-0.2/CF) exhibited a significantly improved specific capacitance of 180.6 F·m⁻² and a low charge-transfer resistance of 5.6 Ω. When applied in an MSMFC, the CNCO-0.2/CF cathode delivered a high power density of 1043.8 mW·m⁻², which was 5.1 times that of the undoped benchmark (NCO/CF), while maintaining stable operation for 45 days. Electrochemical characterizations verified its excellent DORR activity, as demonstrated by a favorable electron transfer number (n ≈ 3.7). The enhanced performance is attributed to the synergistic effects of Cu²⁺ doping, which introduced oxygen vacancies, improved electrical conductivity, and formed a unique nanoneedle array structure. This work offers a promising strategy for designing high-performance, cost-effective cathodes for long-term marine energy conversion.