THE ELECTROCATALYTIC ACTIVITY OF THE HER IN BASIC-MEDIUM ON IRON OR NICKEL ELECTRODEPOSITED WITH HETEROPOLYACIDS (HPAS) - EFFECT OF THE MOLECULAR-MASS OF THE HPAS

Iron was electrodeposited from dilute aqueous solutions of iron sulpha te, containing PW12O403-, PMo12O403- or MoO42- ions. Nickel was electr odeposited from dilute aqueous solutions of nickel chloride, containin g PW12O403- ions. It was shown that the improvement in the overpotenti al and in the exchange current density of the hydrogen evolution react ion (h.e.r.) on the electrodes depends on the nature of the heteropoly acid of the deposition bath. The h.e.r. electrocatalytic activity of t he electrodeposits was then analysed and related to their chemical com position. The results show that some active electrocatalysts are produ ced when combinations of Fe(SiW12) or Fe(PMo12) are formed. The influe nce of the type of the heteropolyacid in the electrode deposition elec trolyte on the electrocatalytic properties of these deposits for the h ydrogen evolution reaction (h.e.r.) was investigated. The effect of [P MoO403-] in the deposition bath on the electrocatalytic properties of the h.e.r. of the electrodes was determined. The best electrocatalytic properties for the h.e.r. are obtained with electrodes electrodeposit ed with 1.8 g l-1 of PMo12O43- for ion and 2.9 g l-1 of PW12O403- for nickel. The electrodes which exhibit the best results are related to t he molecular mass of PMo12O403- or PW12O403-.