Underpotential deposition of copper in acetonitrile

The Under Potential Deposition of Cu on Au (111) in Nonaqueous Acetonitrile

The underpotential deposition (UPD) of Copper on Au(111) in nonaqueous acetonitrile/perchlorate electrolyte has been investigated. The deposition mechanism is thereby strongly influenced by coadsorbed acetonitrile molecules and the stability of the solvation shell around the Cu(I) ions. The UPD mechanism obeys a two step mechanism even in presence of only none specifically adsorbing perchlorate ions. Thereby the first sub monolayer of copper is stabilized by coadsorbed acetonitrile molecules. However already 5% vol water content changes the structure within the double layer and consequently degrades the copper sub monolayer. At about 20% vol water content the Cu(I) ion/solvent complex is still stable. The reduction of Cu(I) ions from this complex is much faster compared to the reduction from the respective Cu(II) water complex.

Peroxide electroreduction on bi-modified Au surfaces: vibrational spectroscopy and density functional calculations

The mechanism of the electroreduction of peroxide on Bi-submonolayer-modified Au(111) surfaces is examined using surface-enhanced Raman scattering (SERS) measurements along with detailed density functional theory (DFT) calculations. The spectroscopy shows the presence of Bi-OH and Bi-O species at potentials just positive of that where peroxide is reduced. These species are not present in solutions absent either peroxide or Bi. DFT calculations show that peroxide is unstable relative to Bi-OH when Bi is present in the (2 x 2) configuration on Au(111) known from previous work to be catalytically active. The spacing between Bi adatoms is such that peroxide association with two Bi cannot occur without O-O bond cleavage. The full Bi monolayer is catalytically inactive and exhibits none of the Bi-OH or Bi-O signals seen for the active surface. The calculations show that as the Bi coverage becomes greater and the Bi adatom spacing becomes smaller, peroxide can adsorb on Bi without O-O bond rupture. These results indicate an important role for M-OH species in peroxide electroreduction.