The voltammetry of surfaces vicinal to Pt{110}: Structural complexity simplified by CO cooling

By flame-annealing and cooling a series of Pt n{110}×{111} and Pt n{110}×{100} single crystal electrodes in a CO ambient, new insights into the nature of the electrosorption processes associated with Pt{110} voltammetry in aqueous acidic media are elucidated. For Pt n{110}×{111} electrodes, a systematic change in the intensities of so-called hydrogen underpotential (Hupd) and oxide adsorption voltammetric peaks (for two dimensionally ordered (1×1) terraces and linear {111}×{111}step sites) point to a lack of surface reconstruction with all surfaces adopting a (1×1) configuration. This is in contrast to hydrogen cooled analogues which give rise to significant residual surface disorder, probably associated with the excess 50% of atoms remaining atop of the surface upon deconstruction of the {110}−(1×2) terrace phase. In contrast, Pt n{110}×{100} stepped electrodes, when cooled in gaseous CO following flame-annealing, show a marked tendency towards surface reconstruction, even at low step densities. Variations in potential of the Pt{110}-(1×1) Hupd electrosorption peaks as a function of specific ion adsorption strength and pH point to weak specific adsorption for both anions (including perchlorate and fluoride) and cations (including Na+ and K+). CO charge-displacement measurements of the potential of zero total charge (PZTC) allow inferences to be made concerning the nature of the electrosorbed species in the hydrogen underpotential deposition (Hupd) region. Hence, a coherent interpretation of the complex voltammetric phenomena often displayed by platinum surfaces vicinal to the {110} plane is proposed. [Display omitted] •Cyclic voltammetry of CO-cooled, stepped Pt{110}−(1×1) electrodes reported.•Weak specific adsorption Na+(aq) and F−(aq) anions observed in aqueous acidic media.•New model of Pt{110} electrosorption behaviour outlined.•CO charge displacement and PZTC predicted a priori using assumption of local charged states.