The first observation of Mo5+ in the passivation layer of Mo2N

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Molybdenum nitride powder with sg of 115 m2·g-1 (passivated) has been prepared by a temperature programmed reaction of MoO3 in H2/N2 mixture. It exhibited high catalytic activity in CO oxidation at low temperature. XPS, EPR and LRS studies have shown the existence of mixed valence states of Mo ions, especially Mo5+ ion (g⊥=1.932, g‖=1.892) observed for the first time, in the passivation layer of molybdenum nitride. A surface superoxide species, O-2(g = 2.001, Raman band 1 124 cm-1), was found to be produced accompanying the transformation of Mo5+/Mo4+ redox pair. Evidence has been given to suggest that this surface superoxide might be responsible for CO oxidation over Mo2N catalyst.
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