By flame-annealing and cooling a series of Pt n{110) x {111} and Pt n{110} x {100} single crystal electrodes in a CO ambient, new insights into the nature of the electrosorption processes associated with P4110} voltammetry in aqueous acidic media are elucidated. For Pt n{110} x {111} electrodes, a systematic change in the intensities of so-called hydrogen underpotential (Hupd) and oxide adsorption voltammetric peaks (for two dimensionally ordered (1 x 1) terraces and linear {111} x {111)step sites) point to a lack of surface reconstruction with all surfaces adopting a (1 x 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 x 2) terrace phase. In contrast, Pt n{110} x [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 x 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. (C) 2016 Elsevier B.V. All rights reserved.