Activity enhancement of Pt/MnOx catalyst by novel β-MnO2 for low-temperature CO oxidation: study of the CO-O2 competitive adsorption and active oxygen species

Low-temperature oxidation of carbon monoxide (CO) is one of the most studied reactions because of its scientific and industrial applications. In this study, we discovered that the low-temperature CO oxidation activity over Pt/MnOx catalyst could be enhanced by a novel beta-MnO2 support material. Nearly complete CO conversion was obtained over the Pt/MnOx catalyst below 100 degrees C under our catalysis conditions. TOF (turnover frequency) of Pt/MnOx was five and nine times that of Pt/MnOx-COM (COM, commercial) and Pt/Al2O3 at 150 degrees C, respectively. The combined results of X-ray diffraction (XRD) Rietveld refinement of fresh and spent catalysts, CO-temperature-programmed desorption (CO-TPD) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy allowed us to conclude that the O-2 molecules exhibited strong adsorption and activation ability on the surface of Pt/MnOx compared to that on the surface of Pt/MnOx-COM. From the H-2-TGA (weight loss) and DTGA results, we confirmed that strong metal-support interactions exist between Pt and MnOx via formation of Mn-O-Pt bonds for both catalysts. Moreover, by combining the results of Rietveld refinement of XRD, Raman, CO-TPD and O-2-TPD (inlet CO and inlet CO/O-2 mixture gases as adsorbates, respectively) analyses, we inferred that the interfacial lattice oxygen in Pt/MnOx might be the active oxygen species for low-temperature CO oxidation.