Membrane-less Direct Formate Fuel Cell Using an Fe-N-Doped Bamboo Internode as the Binder-Free and Monolithic Air-Breathing Cathode.

Commercial applications of direct liquid fuel cells require a high-performance, cost-effective, robust, and mechanically/chemically stable cathode for the oxygen reduction reaction. In this study, a membrane-less direct formate fuel cell (DFFC) was constructed by using a Fe-N-doped bamboo internode as the binder-free and monolithic air-breathing cathode and a Pd-electrodeposited graphite rod as the anode. The effect of the preparation procedures including alkali activation, pyrolysis with (NH4)3PO4, and solvothermal treatment with iron phthalocyanine on the physicochemical properties of the cathode is studied with respect to the textural structure, electrical conductivity, and heteroatom incorporation. The results indicated that the resulting cathode exhibited proper distribution of primary/secondary pores for the transport of reactants and ions. Additionally, these procedures effectively increased the electrical conductivity and heteroatom incorporation in the carbon matrix of the as-obtained cathode. The fabricated membrane-less DFFC delivered an open-circuit voltage of 1.04 V and a maximum power density of 10.01 ± 0.16 mW cm-3 with a limiting current density of 48.95 ± 1.84 mA cm-3. In addition, this DFFC achieved a high columbic efficiency of 92.3% after 7 h of discharge with one-fueling. Furthermore, the 110 h discharge test at 10 mA cm-3 demonstrated that the DFFC fabricated with the Fe-N-doped bamboo internode cathode exhibited good stability, showing its promising application as an inexpensive power supply in portable electronics.