Unraveling surface structures of gallium promoted transition metal catalysts in CO2 hydrogenation
Si Woo Lee, Mauricio López Luna, Nikolay Berdunov, Weiming Wan, Sebastian Kunze, Shamil Shaikhutdinov, Beatriz Roldán Cuenya
Abstract
Abstract Gallium-containing alloys have recently been reported to hydrogenate CO 2 to methanol at ambient pressures. However, a full understanding of the Ga-promoted catalysts is still missing due to the lack of information about the surface structures formed under reaction conditions. Here, we employed near ambient pressure scanning tunneling microscopy and x-ray photoelectron spectroscopy to monitor the evolution of well-defined Cu-Ga surfaces during CO 2 hydrogenation. We show the formation of two-dimensional Ga(III) oxide islands embedded into the Cu surface in the reaction atmosphere. The islands are a few atomic layers in thickness and considerably differ from bulk Ga 2 O 3 polymorphs. Such a complex structure, which could not be determined with conventional characterization methods on powder catalysts, should be used for elucidating the reaction mechanism on the Ga-promoted metal catalysts.