Oxygen vacancies enhance the photocatalytic deep oxidation of NO over an N-doped KNbO3 catalyst†
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Abstract
N-Doped KNbO3 (N-KNbO3) was prepared through mechanical mixing, grinding and calcination of urea and KNbO3. The photocatalytic NO oxidation performance was evaluated at room temperature and under visible light irradiation. Compared with the pristine KNbO3, N-KNbO3 not only has a better NO oxidation performance but also can effectively inhibit the formation of NO2 (electron paramagnetic resonance). EPR tests showed that the doping of non-metallic element N created oxygen vacancies (OVs) on the surface of KNbO3, which was beneficial to the formation of impurity energy levels to reduce the band gap. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results indicated that NO acquired electrons around OVs to form N2O2− intermediates, which were then oxidized by reactive oxygen species (˙OH, ˙O2− and 1O2). Moreover, visible light can promote the activation of NO and O2 and also the formation of OVs. This work provided a new idea for the design and preparation of N-doped photocatalysts for NO photocatalytic oxidation.
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