Enhanced Catalytic Activity of Platinum Electrodes resulting from Cathode Pretreatment

Abstract

A RECENT report^1,2 describes the effect on Raney platinum electrodes of cathodic pretreatment in 10N H₂SO₄. Current-voltage curves for the oxidation of formic acid in 3N H₂SO₄ before and after pretreatment were compared and the enhanced currents measured for the treated electrodes were attributed to an adsorbed layer of sulphur formed by deposition during the cathodic pretreatment. This is surprising because the inhibiting effect of sulphur adsorbed on platinum on many other surface reactions and electrode reactions is well known and was observed by Faraday³. Enhanced catalytic activity was also observed^1,2 by using electrodes pretreated with gaseous hydrogen sulphide at high temperatures and with electrodes cathodically polarized in solutions of selenium oxide in dilute sulphuric acid. Extended cathodic pretreatment in 10 N H₂SO₄ yielded a less active electrode. Here, the sulphur was said to have formed a monolayer.