Facile fabrication of hierarchically porous Ni foam@Ag-Ni catalyst for efficient hydrazine oxidation in alkaline medium

Abstract With the procedure of H2 gas templated electrodeposition and subsequent galvanic replacement reaction, we successfully fabricate the Ni foam@Ag-Ni (Ni foam coated with Ag-Ni bimetals) electrode. Results show the electrodeposition time of 1.5 min produces Ni foam@Ni (Ni foam coated with Ni) with the largest mass specific surface area, and the galvanic replacement time of 8 min yields Ni foam@Ag-Ni with the most favorable catalytic activity toward hydrazine oxidation reaction (HzOR). Materials characterizations reveal the formation of Ag-Ni alloy, the presence of hierarchical pore-structure, the large superficial metallic Ni content and the low amount of Ag mass loading (0.0765 mg cm−2) in Ni foam@Ag-Ni. Electrochemical evaluations show the optimized Ni foam@Ag-Ni electrode delivers the significantly lowest onset potential toward HzOR, with a negative shift of ∼260 mV than Ni foam, ∼220 mV than Ni foam@Ni and ∼60 mV than Ni foam@Ag. Furthermore, it exerts the highest current density in 1.0 mol L–1 KOH and 25 mmol L–1 N2H4, more than 2 fold that of the Ni foam, Ni foam@Ni and Ni foam@Ag at –0.05 V versus Ag/AgCl. The superiority in micro-scale construction and surface composition also endows Ni foam@Ag-Ni electrode with the remarkable durability and considerable whole-cell performance.