Investigations of the electrocatalytic hydrogenation of organic molecules at palladium on nickel cathodes

Voltammetry at rotating and stationary disc electrodes is used to study the deposition of high area palladium on to nickel in an acid chloride bath. Stable deposits are formed although it is shown that on open circuit, the nickel substrate reacts with Pd(II) in the acidic chloride medium to give an immersion coating; both the immersion coating and electrodeposited metal layers are shown to contain nickel as well as palladium. The alloy is much less able than pure palladium to absorb hydrogen and shows different properties as an electrocatalyst. As a result, it may be demonstrated that the behaviour of these surfaces in methanol containing ethanoic acid as a proton source is quite different to that of Pd on C deposits. The palladium on nickel in the methanol medium is, however, a very effective and highly selective cathode for the electrocatalytic hydrogenation of nitrobenzenes to anilines.