Polycrystalline gold electrode redox behavior in an ammoniacal electrolyte- Part II. A parallel RRDE, EQCM and TOF-SIMS study of copper underpotential deposition

The underpotential deposition (upd) of copper at polycrystalline gold in an ammoniacal electrolyte (0.1 M NH3 + 0.1 M NaClO4) was investigated. The ro tating ring disk electrode (RRDE), the electrochemical quartz crystal micro balance (EQCM) and time of flight secondary ion mass spectrometry (TOF-SIMS ) were all used in parallel to study this process. RRDE experiments showed that upd of Cu(0) occurred at -0.4 V < E < 0.1 V, at three different sites. Bulk deposition of Cu(0) began at -0.4 V. RRDE and EQCM data did not show the involvement of any ionic copper species during the upd discharge proces s. Static and dynamic TOF-SIMS results are consistent with the above experi mental results. The rate-determining step is the reduction of a dissolved c opper ammonia species to upd Cu(0). (C) 1999 Elsevier Science S.A. All righ ts reserved.