Developing highly active electrocatalysts with low cost and high efficiency for hydrogen evolution reactions (HERs) is of great significance for industrial water electrolysis. Herein, a 3D hierarchically structured nanotubular copper-doped nickel catalyst on nickel foam (NF) for HER is reported, denoted as Ni(Cu), via facile electrodeposition and selective electrochemical dealloying. The as-prepared Ni(Cu)/NF electrode holds superlarge electrochemical active surface area and exhibits Pt-like electrocatalytic activity for HER, displaying an overpotential of merely 27 mV to achieve a current density of 10 mA cm and an extremely small Tafel slope of 33.3 mV dec in 1 m KOH solution. The Ni(Cu)/NF electrode also shows excellent durability and robustness in both continuous and intermittent bulk water electrolysis. Density functional theory calculations suggest that Cu substitution and the formation of NiO on the surface leads to more optimal free energy for hydrogen adsorption. The lattice distortion of Ni caused by Cu substitution, the increased interfacial activity induced by surface oxidation of nanoporous Ni, and numerous active sites at Ni atom offered by the 3D hierarchical porous structure, all contribute to the dramatically enhanced catalytic performance. Benefiting from the facile, scalable preparation method, this highly efficient and robust Ni(Cu)/NF electrocatalyst holds great promise for industrial water-alkali electrolysis.
The determination of active sites of materials is essential for the molecular design of high-performance catalysts. In this study, the first-principles method is applied to investigate the active sites of low-cost Ni metal-based electrocatalysts for hydrogen evolution reactions (HER), which is a promising alternative to expensive Pt metal-based catalysts. The adsorption of hydrogen on different sites of pristine and partially oxidized Ni(111) surface is investigated. All of the possible configurations have been systematically investigated here with the consideration of their Boltzmann distribution. Using the Gibbs free energy of intermediate H atoms (ΔG H* ) as a descriptor, it is found that the ΔG H* increases with the increase of the coverage of oxygen atoms. The slightly oxidized surface Ni atoms are theoretically identified to be the best catalytic centers for the electrocatalytic HERs when the coverage of oxygen is considerably low. On the basis of the analyses of Bader charge distribution and density of states, our results reveal that the superior performance of the slightly oxidized surface Ni atoms can be ascribed to the optimal electronic properties.
Novel double-shelled Co3O4 yolk–shell submicrospheres were successfully synthesized via a poly-assisted template-free solvothermal method and a subsequent high heat-treatment process.
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