Platinum electrodeposition from H3Pt(SO3)2OH solutions

In this work, an investigation into the electrochemistry of H3Pt(SO3)2OH is reported. Platinum was electroreduced from a solution of this complex acid onto glassy carbon (GC) in preliminary experiments and then onto carbon-black (CB) based electrodes as used in polymer electrolyte membrane fuel cells (PEMFCs). The electrodeposited platinum is believed to be poisoned by a sulphide or retained sulphite species. Platinised electrodes were electrochemically cycled between the hydrogen and oxygen evolution potentials in H2SO4 solution in order to activate the platinum and obtain a reproducible surface area. Strong oxidation and reduction currents were observed during the potentiodynamic cycling treatments indicating gradual removal of the poisoning species. For a comparison, the poisoning effect of sulphite was investigated on both smooth platinum and Pt/GC electrodes using 1 M NaHSO3 solution. The Pt and Pt/GC electrodes were instantly deactivated in NaHSO3 solution and were cleaned in a manner akin to the Pt/GC electrode prepared from electroreduction of H3Pt(SO3)2OH. The platinum redox behaviour and surface area of these sulphite-poisoned electrodes was fully recoverable using the same potentiodynamic cycling treatment. Brief electrodeposition comparisons with other platinum species, viz. H2PtCl6 and Pt(NH3)4Cl2, are also presented. The platinised electrodes were characterised by cyclic voltammetry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDXS).