The promotional effect of potassium in the reverse water gas shift reaction (RWGS) was studied for Pt/mullite catalyst. The addition of potassium on Pt/mullite significantly enhanced the CO2 conversion and hindered the formation of methane as a by-product. The turnover frequency (TOF) at 340 degrees C was enhanced by potassium up to 7 times that of Pt/mullite. TEM observations indicated a slight Pt particle size growth on the K-promoted sample. Characterization results by means of H-2-TPR and XPS revealed the strong interaction between KOx and Pt, which stabilized the Pt in a higher oxidation state. DRIFTS observation under the RWGS conditions suggested that the newly created interface between KOx and Pt served as the active site for formate decomposition to produce CO. The presence of potassium also weakened the strength of CO adsorption on Pt, which hindered the further hydrogenation of CO into CH4 through C-O bond dissociation. (C) 2016 Elsevier B.V. All rights reserved.