Na-based catalysts (i.e., Na2WO4) were proposed to selectively catalyze OH radical formation from H2O and O2 at high temperatures. This reaction may proceed on molten salt state surfaces due to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na2WO4, which can form OH radicals, using in situ techniques including X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometer, and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). As a result, Na2O2 species, which were hypothesized to be responsible for the formation of OH radicals, has been identified on the outer surfaces at temperatures ≥800°C, and these species are useful for various gas-phase hydrocarbon reactions including the selective transformation of methane to ethane.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The research reported in this study was supported by the King Abdullah University of Science and Technology (KAUST). F.T. acknowledges financial support from the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, under Grant No. DE-SC0014561, the U.S. National Science Foundation Career Award NSF-CHE-1462121, and the U.S. National Science Foundation under the grant No. NSF-OIA-1539105.