Polycrystalline gold electrode redox behavior in an ammoniacal electrolyte Part I. A parallel RRDE, EQCM, XPS and TOF-SIMS study of supporting electrolyte phenomena

摘要

The redox behavior of a gold electrode in an ammoniacal electrolyte (0.1 M NH_3 and 0.1 M NaClO_4) was investigated using four techniques. These were the rotating ring disk electrode (RRDE), the electrochemical quartz crystal microbalance (EQCM), X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (TOF-SIMS). Two different gold surface compounds, AuO and AuNH_2, are formed in relative amounts that depend on the holding time at +0.6 V (versus SCE). XPS and SIMS studies were used to distinguish the surface species AuO and AuNH_2 from AuO and AuOHNH_2. When the potential is held at +0.6 V for longer times, other oxidized gold surface species may form, e.g. AuO, AuOHNH_2, [OH(NH_2)Au]_2NH, AuNH_2, Au_2O_3 centre dot 2NH_3 and AuO_3 centre dot 3NH_3. During the gold electrode oxidation process, NH_3 is probably oxidized to N_2. During the surface gold species reduction process. some soluble Au(III) species form that can be reduced to an adsorbed Au(I) species at -0.4 V.