Au(111) Surface Oxidation Kinetics Probed by Electrocatalytic Oxidation of Formic Acid

Abstract

The kinetics of surface oxidation for Au(111) in 0.1 M HCOOH + 0.1 M HClO4 was studied at 20°C utilizing the electrocatalytic formic acid oxidation reaction (FAOR). In the surface oxidation region, cyclic voltammetry shows a distinct dependence of FAOR on scan rate revealing simultaneous deactivation of active surface sites. The surface oxide is essentially inactive for the FAOR. A series of current-time curves was recorded after potential steps into the potential range between 0.65 and 1.00 V vs. saturated mercury-mercurous sulfate electrode and analyzed within a three-step surface oxidation model, which successively involves (i) adsorption at surface defects, (ii) adsorption on well-defined Au(111) terraces, and (iii) two-dimensional nucleation-and-growth on terraces. Although Au surface oxidation is by far more complex, the system can be described in terms of the intrinsic activity of the Au(111) surface and the oxide coverage. The chronoamperometric measurements can be modeled without considering the interaction of the oxide species with the FAOR and the co-adsorption of anions. The potential dependence of the kinetic parameters is used to obtain theoretical current-time curves for FAOR on Au(111). This study sheds light on the "fast FAOR" and contributes to the understanding of degradation phenomena in electrocatalysis

Metal deposition and electrocatalysis for elucidating structural changes of gold electrodes during cathodic corrosion

“…The formation of wide Au(111)-terraces is evident from the appearance of this kink, which is characteristic of large and well-ordered Au(111) single crystal surfaces. 45,62 These results demonstrate that cathodic corrosion of Au in KOH leads to the formation of much wider Au(111)-terraces compared to NaOH. Moreover, the trend observed for this kink is in excellent agreement with the systematic series of sulfate spikes for Au in H 2 SO 4 (Fig.…”

“…5b). 45,62 Interestingly, this kink is sharper as more (111)-facets are present on the electrode surface. The formation of wide Au(111)-terraces is evident from the appearance of this kink, which is characteristic of large and well-ordered Au(111) single crystal surfaces.…”

“…43 Similarly, FAOR has been used to examine the alterations upon adsorption and self-assembly of the 4-mercaptopyridine on Au(111), as well as to monitor the kinetics of surface oxidation of Au(111). 44,45 Furthermore, hydrogen and formic acid are ideal energy carriers, that have garnered considerable attention as prototype reactions in the advancement of sustainable energy technologies. 46 Thin metal overlayers on well-defined substrates have emerged as promising model systems in electrocatalysis, showcasing remarkable influences of the substrate's chemical nature and crystallographic orientation, as well as the overlayer thickness, on electrocatalytic activity.…”

“…43 Similarly, FAOR has been used to examine the alterations upon adsorption and self-assembly of the 4-mercaptopyridine on Au(111), as well as to monitor the kinetics of surface oxidation of Au(111). 44,45 Furthermore, hydrogen and formic acid are ideal energy carriers, that have garnered considerable attention as prototype reactions in the advancement of sustainable energy technologies. 46…”