A study of the electrocatalytic behaviour of gold in acid using ac voltammetry

ac voltammograms were recorded for gold in different strong acids both in the absence and presence of various oxidants and reductants. Two incipient hydrous oxide species were assumed to be involved: a similar conclusion was reached earlier for gold in base. The first was a cationic Au(I) species that is stable to quite low potentials; the reversible potential for formation of this species is too low to be of interest in most electrocatalytic reactions in acid. However, this lower oxide is apparently an inhibitor of S 2O 2− 8 reduction. The second product, formed by oxidation of low coverage Au adatoms, can exist in two different forms: analogous behaviour was again noted earlier for this metal in base. The Au(III) products were observed to mediate oxidations, and inhibit reductions, of different species at two distinct potentials, one at ca 0.8 V( rhe) and the other at ca 1.0 V( rhe). The latter conclusions were supported by dc investigation of the same processes.