Construction of core-shell Ni-Co(OH)F@NiCo2S4 nanorods for highly efficient hydrazine-assisted hydrogen evolution

Electrochemical hydrazine-assisted water electrolysis is an effective strategy for hydrogen production. However, the great energy consumption of electrolysis is still a challenge, which imperatively needs the rational design of highly efficient electrocatalysts. Herein, the synthesis of novel Ni-Co(OH)F@NiCo2S4 nanorods is reported via the hydrothermal method and subsequent controllable sulphuration process. The Ni-Co(OH)F@NiCo2S4 nanorods are composed of Ni-Co(OH)F cores (similar to 70 nm diameter) and NiCo2S4 shells (similar to 65 nm thickness). The experiments confirm that Ni doping and core-shell interface engineering can synergistically accelerate electron transfer, optimize the H adsorption/desorption behaviors, and thus boost the catalytic performance in hydrazine-assisted hydrogen evolution. The resultant Ni-Co(OH)F@NiCo2S4 nanorods show a low overpotential (eta(10) = 97 mV) and small Tafel slope (58 mV dec(-1)) for alkaline hydrogen evolution. Besides, the Ni-Co(OH)F@NiCo2S4 nanorods can output 10 mA cm(-2) current density for the hydrazine oxidation reaction at working potentials of 20 mV (0.1 M hydrazine and 1.0 M KOH) and -49 mV (1.5 M hydrazine and 1.0 M KOH), respectively. An ultralow cell voltage of 250 mV is required to achieve a current density of 10 mA cm(-2) in a hydrazine-assisted hydrogen evolution system.