The effects of pretreatment of polycrystalline gold with OH• radicals on the electrochemical nucleation and growth of platinum

Abstract

The nucleation and growth of platinum on polycrystalline gold was studied by chronoamperometry, cyclic voltammetry, and atomic force microscopy before and after treatment of the gold surface with hydroxyl (OH • ) radicals. Two different procedures of mechanical polishing of the gold surface ("coarse polish" and "fine polish") were applied before the treatment with OH • radicals. The nucleation and growth of Pt was much better reproducible on electrodes which underwent a "coarse polish". The treatment of the Au surface with OH • radicals decreased the number of active sites; however, the nucleation growth mode remained the same (3-D instantaneous). The spontaneous Pt deposition (no externally applied potential) on Au was unaffected by the treatment with OH • radicals. In situ atomic force microscopy experiments showed that the Pt starts to grow only on some of the Au grains, most probably on those which have active sites on their surface. This leads to a roughening of the electrode surface upon Pt deposition. Treatment with OH • radicals did only quantitatively diminish the amount of deposited Pt, but qualitatively the imaging of the Pt growth remained the same. Obviously, the OH • radicals lead to a knockout (decreasing number) of active sites for Pt nucleation, while the nature of the remaining active sites stays unaffected.

Probing the surface oxidation of chemically synthesised gold nanospheres and nanorods

“…• radicals resulted in a reduction in the number of active sites for Pt nucleation [29]. Prior to this work, Kolb investigated the cyclic voltametric behaviour of single crystal gold surfaces where it was found that there was a significant peak prior to the monolayer oxide formation process that could be attributed to the level of surface defects which were step edges on Au(111) electrodes [30,31].…”

Gold dissolution: towards understanding of noble metal corrosion

“…Also other aspects, as for instance a possible effect of formation of hydroxyl radicals initiating and/or accelerating gold dissolution should be included. [69][70][71][72] Nevertheless, the proposed models can capture all the experimentally observed aspects of gold dissolution described in this work. In summary, the local de-passivation of the surface during oxide formation/reduction as well as oxygen evolution is determining transient and steady-state dissolution of gold, respectively.…”

Grain boundary corrosion of the surface of annealed thin layers of gold by OH· radicals

“…may be responsible. Here, a comparison of the present results with those of our earlier electrochemical studies is very interesting: in previous studies, we have shown that at poly-crystalline gold, OH · radicals (1) preferably knock out active sites of electrocatalytic reactions (oxygen and hydroquinone reduction), and (2) they also knock-out the active sites for platinum deposition [1][2][3]. Hence, there is the possibility that the active sites for electrocatalysis and electrodeposition may be non-Au{111} faces, i.e., grain boundaries or locations with high defect concentrations.…”

“…Previously, we have reported on the interaction of OH · radicals with the surface of poly-crystalline noble metals (Au, Pt, Pd, and Ag) [1][2][3] and glassy carbon [4]. Particular attention was given to alterations of the surface morphology, the electrocatalytic properties, and the properties of the surfaces in nucleation growth of metal deposition [1,5].…”