The deposition of mesoporous Ni/Co alloy using cetyltrimethylammonium bromide as the surfactant in the lyotropic liquid crystalline phase bath

The procedure for the electrodeposition of a mesoporous nickel/cobalt layer from a liquid crystalline plating bath based on the cheap, commercial surfactant, cetyltrimethylammonium bromide and an aqueous solution containing 0.84 M NiCl2 and 0.20 M CoCl2, has been investigated. The phase diagram for these mixtures is reported and it is shown that the H1 liquid crystalline phase has a high conductivity. The conditions for deposition have been established using cyclic voltammetry and potential step and deposits are characterised using scanning electron microscopy (SEM), electron diffraction analysis (EDX) and helium ion microscopy (HIM). Uniform thickness deposits with a Ni/Co ratio ∼4/1 can be prepared and they have a high surface area; in 1 M NaOH Ni/Co alloy layers with a thickness of ∼2 μm can store ∼1 C cm−2 in the Ni(OH)2/NiOOH couple. This charge may be cycled >20 times.