In a recent review article, it was suggested that a redox mechanism best describes observations regarding the WGS reaction for metal promoted ceria systems, as well as how molecules such as CO, CO2, H2O, and H-2 interact with the ceria surface. In this contribution, the pretreated surface of Pt/ceria was subjected to steaming or H-2 treatment at 250 A degrees C followed by CO adsorption after six different pre-treatment sequences were performed. Subjecting a H-2-treated surface directly to CO, or followed by steaming, led to the highest concentration of surface formates by reaction of CO with Ce3+ defect-associated Type II bridging OH groups. The Type II OH groups were also generated by CO treatment followed by steaming. Using CO as a probe led to a significant coverage of formate species, though less than the previous cases (CO added to a H-2 treated surface or a surface treated with H-2, then H2O). Surprisingly, even subjecting an oxidized surface (pre-reduced and subjected to O-2 at 400 A degrees C) to steam still produced a significant density of Type II OH groups, as evidenced by the formates produced upon exposure to CO. The formates were easily decomposed in steam at 130 A degrees C and converted to carbonate species. Thus, focusing on the turnover of formate via C-H bond breaking offers important possibilities for future catalyst development.