Electrochemical Preparation of a Au Crystal with Peculiar Morphology and Unique Growth Orientation and Its Catalysis for Oxygen Reduction

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Abstract
Gold nanocrystals with a peculiar pin-like morphology have been obtained on glassy carbon (GC) electrodes by electrochemical deposition from 0.5 M H2SO4H2SO4 solution containing 1.0 mM Na[AuCl4]Na[AuCl4] in the presence of cysteine as an additive. The amount of such electrodeposited Au particles as well as the particle size increased with the increase of deposition time (td)(td) . Crystalline facets of Au(100) and Au(110) were significantly enriched in the presence of cysteine during the electrodeposition, and the Au crystals grew along a unique crystalline orientation of Au(111). Finally, Au crystals (with the average diameter of ca. 100 nm and length of ca. 1660 nm at td=2000std=2000s ) with a peculiar pin-like morphology were obtained, in contrast to the plump Au particles prepared in the absence of cysteine. The cathodic peak current density for the O2O2 reduction in acidic electrolyte (0.5 M H2SO4H2SO4 ) at the Au crystals-electrodeposited GC electrode prepared in the presence of cysteine was larger than that at the electrode prepared in its absence. This behavior could be reasonably explained in view of the higher specific surface area of the Au crystals prepared in the presence of cysteine than those prepared in the absence of cysteine.