Phase-engineering of nickel hydroxide in the Ni/Ni(OH)2 interface for efficient hydrogen evolution and hydrazine-assisted water splitting in seawater†
*ab
Abstract
The alkaline hydrogen evolution reaction (HER) activity of layered metal hydroxides is not satisfactory due to their poor electrical conductivity and limited active sites. Taking Ni(OH)2 as a typical example, density functional theory (DFT) calculations are first performed to confirm that the phase engineering of Ni(OH)2 (α-Ni(OH)2 and β-Ni(OH)2) can effectively optimize hydrogen adsorption, with β-Ni(OH)2 showing better HER activity. It is also predicted that the electrical conductivity and Volmer step in the HER can be efficiently improved when loading Ni nanoparticles on the surface of Ni(OH)2. Based on DFT calculations, heterostructured Ni/α-Ni(OH)2 and Ni/β-Ni(OH)2 nanosheet arrays (NSAs) are experimentally constructed. Compared to Ni/α-Ni(OH)2 NSAs, the Ni/β-Ni(OH)2 NSAs exhibit enhanced HER activity with a small overpotential of 58 mV and 62 mV to achieve 10 mA cm−2 in alkaline solution and alkaline seawater, respectively. Moreover, the Ni/β-Ni(OH)2 NSAs also manifest better hydrazine oxidation reaction activity than Ni/α-Ni(OH)2 NSAs. Impressively, when Ni/β-Ni(OH)2 NSAs are applied as a bi-functional electrocatalyst for hydrazine-assisted water splitting, only a small voltage of 0.16 V/0.24 V is needed to deliver 10 mA cm−2 in alkaline solution/alkaline seawater.
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