No abstract

Electrocatalysts composed of Pt, and combined RhPt and RuRhPt sub-monolayers deposited on Au/C nanoparticles, were investigated for the electro-oxidation of ethanol. The Au/C substrates were characterized by transmission electron microscopy (TEM) and X-ray absorption near edge structure (XANES) in situ. The electrochemical activity and the products of the ethanol electro-oxidation were investigated by online differential electrochemical mass spectrometry (DEMS). TEM analysis of the Au/C substrate indicated a homogeneous dispersion of the Au atoms onto the carbon support, with particle sizes varying from 5 to 10 nm. The XANES results have evidenced lower increase of the Pt white line magnitude for the mixed layers as the electrode potential was increased. This was associated to a lower oxide formation at the Pt surface due to the presence of neighboring Rh and Ru atoms. Electrochemical stripping of adsorbed CO showed higher activities for the mixed layers as compared to the pure Pt layer and to Pt/C. The electrochemical results for the ethanol electro-oxidation evidenced very similar onset potential for the mixed sub-monolayers and Pt/C. DEMS measurements pointed out a negligible signal of CO 2 for the pure Pt layer but an efficiency improvement for the CO 2 formation when Rh was present on the electrocatalyst surface. The deposition of a second Pt layer induced a slight increase in the electrocatalyst activity and CO 2 formation, which approached to that of Pt/C. It was demonstrated that the electrocatalyst efficiency can be hampered by optimizing the particle shell composition.