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Updated: Jul 13, 2026

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts
Published on: August 7, 2018
Energy transfer on the MgO surface, monitored by UV-induced H2 chemisorption
Martin Sterrer1, Thomas Berger, Oliver Diwald
1Institut für Materialchemie, Technische Universität Wien, c/o Veterinärplatz 1/GA, A-1210 Vienna, Austria.
Abstract:
Surface anions on edges (4-coordinated = 4C) and on corners (3-coordinated = 3C) of cubic MgO nanoparticles exhibit UV resonance absorptions around 5.5 and 4.6 eV, respectively. After monochromatic excitation of either site the electron paramagnetic resonance (EPR) spectrum exhibits exclusively signal components related to 3-coordinated O- radicals (O-(3C), electron hole centers), which are perfectly bleached by H(2) addition. The disappearance of the O-(3C) EPR signal components is paralleled by a depletion of the UV resonance absorption of the 3-coordinated O(2-) only and the appearance of one single band in the OH stretching region of the IR spectrum. Obviously the sites of UV excitation and subsequent UV induced surface reaction with H(2) are not the same. This may coherently be explained in terms of mobility of the exciton (O(2-)(4C)* or--after ionization--of the corresponding electron hole O-(4C) along the edge where it was created. Finally the mobile state is trapped at a corner site where the O(3C)H group is formed.
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