Superaerophobic CoP Nanowire Arrays as a Highly Effective Anode Electrocatalyst for Direct Hydrazine Fuel Cells

One of the major challenges in developing direct hydrazine fuel cells (DHzFCs) is the creation of highly efficient, robust, and inexpensive electrocatalysts with a superaerophobic property for the hydrazine oxidation reaction (HzOR). Herein, a cobalt phosphide nanowire array (CoP-NWA@CP) is grown on a carbon paper substrate as a highly efficient electrocatalyst for the HzOR in alkaline medium, which features a superaerophobic surface that is highly antigaseous and conducive to nitrogen evolution (a gaseous byproduct of the HzOR). The catalyst demonstrates a significant HzOR performance with an onset potential of −61 mV (vs RHE), an ultralow overpotential of −32 mV@10 mA cm–2, and superior stability with little current density loss over 10,000 s at an overpotential of 0.42 V (vs RHE). The remarkable HzOR performance of the CoP-NWA@CP catalyst is attributed not only to its high intrinsic activity but also to its nanowire array design, which offers a large specific surface area and rapid electron and mass transfer, as well as its superaerophobic surface wettability to expedite the release of N2 from the catalyst surface. Furthermore, a DHzFC is constructed using the CoP-NWA@CP catalyst as the anode and commercial MnO2 as the cathode, which delivers a high open-circuit voltage of 0.905 V, a remarkable power density of 300 mW cm–2, and 95% retention after 12.5 h operation, suggesting great potential of CoP-NWA@CP in practical applications.