Platinum electrodeposition from H₃Pt(SO₃)₂OH solutions

Abstract

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).