NEW FINDINGS ON HYDROGEN AND ANION ADSORPTION AT A PT(111) ELECTRODE IN AQUEOUS H2SO4 SOLUTION GENERATED BY TEMPERATURE-VARIATION

Temperature dependence studies of the under-potential deposition of H (upd H) and anion adsorption on Pt(111) in 0.5 M aqueous H2SO4 solutio n by cyclic voltammetry (CV) indicate that the overall adsorption-deso rption charge density is only slightly affected by temperature T varia tion, and that it decreases by 25 mu C cm(-2) when T is raised from 27 5 to 338 K. Introductory deconvolution of the CV into two components a ssigned to the upd H and the anion adsorption indicates that the charg e density associated with the upd H decreases by 20 mu C cm(-2), where as that of the anion adsorption decreases by only 5 IJ C cm(-2). The p otential of the sharp peak in the potential region corresponding to th e anion adsorption shifts towards more positive values upon T increase and the peak current density shifts towards lower values. The behavio ur of the third, asymmetric peak in the double layer region is complex ; the anodic and cathodic components shift towards less positive poten tials but the displacement of the anodic one is more pronounced. The r esults indicate that the H-upd and anion surface coverages theta(Hupd) and theta(AN) respectively are slightly temperature dependent; this b ehaviour may be assigned to weak lateral repulsive interactions. (C) 1 997 Elsevier Science S.A.