Scope for new applications for gold arising from the electrocatalytic behaviour of its metastable surface states

Abstract

The electrocatalytic behaviour of gold in aqueous media is surprisingly complex and a novel view of gold electrode surfaces is proposed to explain the observed electrochemical responses. The metal surface is considered as a chemically (or redox) modified electrode, with equilibrated, low energy, surface gold atoms functioning as a relatively inert support and low coverage, high energy, protruding gold atoms (or minute clusters of same) functioning as electrocatalytic redox mediators. The protruding atoms are viewed as surface active sites and the complex electrocatalytic behaviour is attributed to the basic instability of the mediators, the diversity (and poor control) of same, and the acid/base (or hydrolysis) behaviour of the oxidized states of the mediators. It is assumed that major advances in the application of gold in the heterogeneous catalysis of gas phase reactions will be accompanied by similar advances in the use of gold in the electrocatalysis area; however, this will require considerable work of both a practical and theoretical nature.

Probing the surface oxidation of chemically synthesised gold nanospheres and nanorods

“…However, numerous studies have shown that gold is not as inert as its d 10 configuration suggests which accounts for its pronounced catalytic and electrocatalytic activity [6,[17][18][19][20][21][22][23][24]. This has been attributed to active sites on the surface that consists of atoms or clusters of atoms that have low co-ordination number and have the ability to partake in electrocatalytic reactions [21,22,25,26]. Recent work by Scholz has demonstrated in the case of gold that active or defect sites are located on the asperities of an electrode surface which are the loci of partially filled d orbitals that can stabilise free radical intermediates [27,28].…”

Selective Knockout of Gold Active Sites

“…It has long been known that the activity of electrodes (and of heterogeneous catalysts) is associated with surface defects [1][2][3][4][5][6][7][8][9]; platinum black is a familiar example [10]. In contrast, deactivation is typically achieved by "brute-force" methods such as total passivation [11,12].…”

Voltammetric determination of total dissolved iron in coastal waters using a glassy carbon electrode modified with reduced graphene oxide, Methylene Blue and gold nanoparticles

“…Therefore, 0.1 M solutions of H 2 SO 4 , HClO 4 , HNO 3 , and HCl were chosen as the possible electrolytes. Among them, HCl was the best choice for Fe(III) detection because Cl − can be adsorbed on the AuNPs in the potentials more positive than 0.0 V, which may increase the electron transfer by bridging mechanism [31]. Because the pH value of HCl is an important factor affecting the signal response of Fe(III), the effect of the pH value of the solution on the electrochemical response of 10 μM Fe(III) at the rGO/MB/ AuNPs composite modified GCE was examined in various HCl solution at pH of 2.97, 1.99, and 0.98, respectively.…”