Kinetics of dissociative adsorption of ethylene glycol on Pt(1 0 0) electrode surface in sulfuric acid solutions

Abstract

The dissociative adsorption of ethylene glycol (EG) on Pt(1 0 0) electrode surface cooled in air after flame annealing was investigated by using programmed potential step technique and in situ FTIR spectroscopy. The stable adsorbates derived from EG dissociative adsorption on Pt(1 0 0) were determined by in situ FTIR spectroscopy as linear- and bridge-bonded CO. The quantitative results demonstrated that the average rate of dissociative adsorption of EG on Pt(1 0 0) surface varies with electrode potential, yielding a volcano-type distribution with a maximum value located near 0.10 V versus SCE. From the variation of the quantity of CO adsorbates generated in EG dissociative adsorption with the adsorption time t ad, the initial rate ( ν i) of this surface reaction was evaluated quantitatively. The maximum value of ν i has been determined to be 2.64 × 10 −11 mol cm −2 s −1 in a solution containing 2 × 10 −3 mol L −1 EG. The influence of the surface structure of Pt(1 0 0) electrode obtained by different pretreatment as well as of the specific adsorption of (bi)sulfate anions on the kinetics of EG dissociative adsorption has been also investigated and discussed. In comparison with a Pt(1 0 0) surface cooled in air atmosphere after flame treatment, the Pt(1 0 0) surface cooled in an Ar–H 2 stream or subjected to a treatment of fast potential cycling decreased significantly the initial rate ν i of EG dissociative adsorption. Similar effect was also observed for the specific adsorption of (bi)sulfate anions. However, the maximum attainable coverage ( θ DA S ) of adsorbates derived from EG dissociative adsorption is not affected either by the surface structure of Pt(1 0 0) or by (bi)sulfate anions adsorption.