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.