Photocatalysis Study Of Cu₂ O/TiO₂ Composite Film Prepared By Direct Current Reactive Magnetron Sputtering

Photocatalysis of semi-conductor oxides has become one of the most potential fields in recent years. TiO₂ was widely applied in photocatalysis owe to its non-toxic, stability, low price and thoroughly degradating in organic. However, as a kind of N-type semi-conductor with wide forbidden band gap, TiO₂ could only be excited by UV,which diminished the utilization of sunlight. Moreover, the rapid combination of hole and electron results in poor efficiency of photocatalysis. Plenty of studies have proved that combinating TiO₂ with some narrow band gap semi-conductor could not only improve the separation of electron and hole, but also increase usage of sunlight because the different position of CB and VB in the two semi-conductors. Cu₂O is a nonstoichoimetric p-type semiconductor, major attraction of cuprous oxide is that it is inexpensive, non-toxic, readily available, and which has a direct forbidden bandgap of about 2.2 eV and a highly optical absorption coefficient.TiO₂/Cu₂O composite films were deposited on slide glass by direct current (DC) reactive magnetron sputtering with parameter gradually optimizing in this paper. Energy-dispersive spectrometry (EDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to characterize composition, structure and morphology of the films respectively. Photocatalytic activity was evaluated by the degradation of methylene blue (MB) with xenon lamp; the XRD showed that the crystal of Cu₂O existed preferred growth during sputtering, it was proved that the different crystal face exhibits different catalytic ability, (111) was better than (110) and (220). Therefore, the sputtering time should be controlled in 5min. The experimental results showed that the photocatalytic degradation activity of MB for the Cu₂O/TiO₂ series increased with increasing Cu₂O-deposited content, and then decreased when the content of TiO₂ was constant. The best film was obtained for Cu₂O(2.6%)/TiO₂ and the degradation achieved 73.6% in 60 minutes in our experiment. The two oxidations can't form composite completely with sufficiently Cu₂O, and excess Cu₂O deposited on TiO₂ will prolong the transferring path of the electrons and holes, and which would reduce the quantum efficiency. The experiment of varing different gas value has proved that the effect is better in atmosphere of air than N₂, which is attributed to the increasing lifetime of the charge carrier; The influence of different initial pH appears more obvious, because the base circumstance is advantageous in ^OH generating, and make MB be prone to adsorption and the hole transfer to surface of film easily, which was responsible for the differences in photocatalytic activity. The degradation of MB was 97.4% at pH=12 in 60 minutes.