A series of MSe2-dien (M = metal(ii) ion and dien = diethylenetriamine) were grown on Ni foam (NF) based on Co(ii)/Mn(ii) salts with different molar ratios.

Ni-doped Co(HPO)(OH) with different morphologies was directly grown on Ni foam hydro(solvo)thermally under different synthetic conditions. The optimum condition is solvothermal reaction for 6 h in an ethanol/water (EW) mixed solution, the molar ratio of NaHPO/Co(NO) being 0.5:0.1, and the obtained S0.5-6 h-EW shows three-dimensional (3D) porous nanowire bundles. Whereas in the water-only solution, microrods are obtained, suggesting that the nanowires in bundles are aggregated together via the lateral (400) direction. Long reaction time and low molar ratio of reactants are all beneficial for the lateral growth of the nanowires, and the possible formation mechanism is proposed. All the obtained Ni-doped Co(HPO)(OH)/Ni foam samples are directly used as supercapacitor electrodes, and S0.5-6 h-EW shows the best electrochemical performance with a specific capacity of 159 mAh g at 0.5 A g, which is close to the theoretical value of 212 mAh g for Co(HPO)(OH), and it is the largest reported value so far. The excellent capacitive behavior of S0.5-6 h-EW is ascribed to the 3D porous nanowire bundles directly grown on a Ni foam collector without an additive and a binder, as well as to the doping of Ni into the cobalt phosphite. The S0.5-6 h-EW//activated carbon asymmetrical supercapacitor shows a maximum energy density of 58.7 Wh kg at a power density of 532 W kg and good cycling stability with the capacity retention of 90.5% after 10 000 charging-discharging cycles at 5.5 A g.

Free-standing (Co, Ni)2P/LaF3 hollow nanotube arrays are directly grown on Ni foam (NF) (denoted as (Co, Ni)2P–La4/NF, where “4” refers to 4 g L–1 of La3+ in the starting material), which exhibits efficient electrocatalytic activity for hydrogen evolution reaction (HER) with an overpotential of 94 mV at 10 mA cm2, Tafel slope of 88 mV dec–1, and superior long-term durability in alkaline electrolyte. Investigated was La dosage-induced compositional and morphological evolution of (Co, Ni)2P/LaF3, and it was found that suitable La dosage is beneficial for the epitaxial growth of (Co, Ni)2P on LaF3 nanosheets (the thickness direction of LaF3 nanosheet is along the (03i̅) facet), leading to the formation of porous (Co, Ni)2P/LaF3 nanotube walls, giving rise to hollow nanotube arrays. The binder-free (Co, Ni)2P–La4/NF electrode with unique morphology not only provides more active sites exposure to electrolyte ions and accessible ion diffusion path but also favors electron and charge transfer. Density functional theory calculation and experimental data reveal the doping of La into metal phosphide can lead to electron transfer from metal centers to P atoms, make the ΔG H on the P sites closer to zero with lower H2O adsorption energy (−0.58 eV), thus improving the HER behavior. The present work gives a novel strategy to design hollow nanotubular microstructure as non-noble-metal HER electrocatalyst.

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