The adsorption of on platinum covered with adsorbed hydrogen atoms gives rise to an adsorbate called “reduced ,” written . The steady‐state adsorption of (the isoconcs) and its initial adsorption kinetics (Tafel plots) were studied by radiometric methods employing C14‐labeled . Radiometric results and selected reported electrochemical results appear to be compatible provided the adsorbate , is assumed to be a carbonyl species that is bridged on two adjacent platinum sites. Isoconcs (coverage vs. potential relation) reveal a gaussian curve with a steady‐state adsorption peak between 0.00 and 0.10V (RHE). Both the steady‐state adsorption and kinetic rates increase with pH. No current is observed during the formation of . The character of the isoconcs and the initial kinetic rates are predicted by a reaction scheme based on cathodic reduction of carbon dioxide and anodic oxidation of adsorbed hydrogen atoms in equal amounts.