The catalytic oxidation of hypophosphite on nickel studied by electrochemical mass spectrometry

Abstract

A novel on-line technique of electrochemical mass spectrometry (EMS) combined with isotope labelling was applied for the study of catalytic hypophosphite oxidation on nickel by D 2O within the potential range from −0.1 to −1.2 V. The effect of the nickel potential on the isotopic composition of the gas and a correlation of the latter with the current density indicate that the catalytic process consists of two simultaneous electrochemical reactions — anodic hypophosphite oxidation and cathodic reduction of water — with a charge transfer through the catalyst surface. The weak dependence of the formation rate of light hydrogen on the nickel potential corresponds to a possible limiting step in the anodic half-reaction. The deuterium formation rate showed electrochemical behaviour, although it was accelerated by an increase of the hypophosphite concentration. The influence of the additional cathodic process on the isotopic composition of the gas was observed under open circuit conditions. The feasibility of EMS for the investigation of electroless plating mechanisms has been demonstrated.