Preparation of the composite LaNi3.7Al1.3/Ni–S–Co alloy film and its HER activity in alkaline medium

The composite LaNi3.7Al1.3/Ni–S–Co alloy film was prepared by molten salt electrolysis and aquatic electrodeposition orderly. With Na3AlF6–La2O3–Al2O3 (91:8:1) system as molten salt electrolyte, the LaNi3.7Al1.3 alloy film was obtained by galvanostatic electrolysis at 100 mA cm−2. The results showed that the La3+ and Al3+ ions could be co-reduced on the nickel cathode to form LaNi3.7Al1.3 film, i.e. La3+ + 1.3Al3+ + 6.9e + 3.7Ni = LaNi3.7Al1.3 at c.a. −0.5 V, which is much lower than that of the theoretical decomposition potential of lanthanum and aluminum. With high HER activity, the composite LaNi3.7Al1.3/Ni–S–Co film (η150 = 65 mV, 353 K) could absorb large amount of H atoms, which would be oxidized and therefore effectively avoid the dissolution of the Ni–S–Co film under the state of open-circuit and consequently prolong the lifetime of the cathode.