Abstract
Continuous wave (CW) and pulsed electron paramagnetic resonance (EPR) spectroscopy are used to investigate the nature of vanadium species on V2O5/TiO2 catalysts prepared via wet impregnation and gas-phase grafting routes. CW EPR experiments show in both cases the formation of VO2+ vanadyl ions upon reaction with ammonia; moreover, phase memory time filtered echo-detected EPR experiments at X- and Q-band frequencies provide direct experimental evidence for the reduction of the TiO2 substrate and the formation of Ti3+ ions. X-band hyperfine sublevel correlation (HYSCORE) experiments are used to investigate the local environment of VO2+ ions. The direct nitrogen coordination of residual ammonia fragments in the equatorial plane of the vanadyl ion is demonstrated.
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