Using subtractively normalised interfacial FTIR spectroscopy (SNIFTIRS), we report the unusual behaviour of polycrystalline copper in the presence of dissolved carbon monoxide (GO). Mechanically and electrochemically polished copper electrodes were used in buffered phosphate solution(pH similar to 7). CO was found to interact with the copper surface in two modes : linear-bonded with the oxidised surface at about 2107 cm(-1) and bridged-bonded in the range 1885-1950 cm(-1). Linear-bonded CO occurs at potentials more positive than -0.25 V vs. SCE; a low value compared to that in the range of -0.6 to -0.8 V vs. SHE reported by other authors. Bridge-bonded CO was observed at potentials as negative as -1.0 V vs. SCE. Linear-bonded CO did not show any potential dependence whereas the bridge-bonded species exhibited a shift consistent with the theory of electronic back-donation. Infrared spectra, cyclic voltammetry and chronoamperometric data point to the formation of a copper carbonyl species during the anodic polarisation of the copper electrode and that such species are dissociatively adsorbed during the negative sweep.