Photodegradation of Stearic Acid Adsorbed on Copper Oxide Heterojunction Thin Films Prepared by Magnetron Sputtering

Abstract

Nanocrystalline copper oxide thin films were fabricated by reactive DC magnetron sputtering. The structure and optical properties of the films were measured with X-ray diffraction, scanning electron microscopy, and spectrophotometry. Variations of oxygen partial pressure resulted in oxide composition ranging from Cu, Cu-Cu2O, Cu2O-CuO1−x, and CuO. Optical band transitions at 2.06 eV and 2.55 eV were found for Cu2O corresponding to the direct forbidden and direct allowed interband transitions. For CuO an indirect allowed interband transition was found at 1.28 eV. The photocatalytic activity was determined by quantifying the rate constant and quantum yield (destroyed molecules/photons absorbed) under stearic acid degradation. Photocatalytic activity was found to be highest in mixed-phase films with Cu-Cu2O films the highest. Results from post-annealed Cu-Cu2O and CuO films show similar results. We interpret our results as being due to efficient electron-hole charge separation in the heterojunction films. The obtained quantum yields were generally about ten times lower than for comparable dense TiO2 and WO3 binary oxides, which calls for further studies of the spectral dependence of the quantum yield and electron-hole pair life times for oxides with different purity levels.

Copper–zinc oxide heterojunction catalysts exhibiting enhanced photocatalytic activity prepared by a hybrid deposition method

“…Table 2 shows that quenching of the deep level emission (expressed by the DL/D 0 X intensity ratio) is much less pronounced using wet-chemically prepared ZnO nanoparticles deposited on Cu 2 O films prepared by magnetron sputtering as described elsewhere, 13 emphasizing the importance of physically well-connected Cu 2 O and ZnO interfaces for efficient interfacial charge transfer.…”

“… 8,12 At elevated temperatures it is possible to successively obtain CuO, Cu 3 O 4 , and eventually CuO 2 . 13 The Cu particle deposition rate was calibrated by independent deposition of Cu nanoparticles on a flat glass substrate and the resulting film thickness was determined by profilometry (Bruker DektakXT). In this way, the equivalent thickness of the Cu 2 O layer that was deposited on the ZnO-NRs was estimated to be 36.7 ± 1.3 nm.…”

Effect of the Titanium Isopropoxide:Acetylacetone Molar Ratio on the Photocatalytic Activity of TiO2 Thin Films

“…Degradation of SA is known to follow first-order kinetics, i.e., the integrated band area (A) depends on time as follows: A(t) = A 0 e −kt , where k is photodegradation rate constant. The photodegradation rate constant is the slope value of the linear fit of the plot ln(A/A o ) versus t [53]. The degradation of stearic acid by TiO 2 at the TTIP:AcacH molar ratio 1:4 and determination of the photodegradation rate constant are presented in Figure 6.…”

Heterogeneous Photocatalysis

“…The authors remarked that heterojunction films were more difficult to fabricate, which was explained in terms of a thermodynamic driving force to form single-phase oxide. The well-structured control that can be obtained using magnetron sputtering will be fully exploited in the coming years while considering a definitive dependence of the superficial structure in the photocatalytic process [17].…”

“…The authors remarked that heterojunction films were more difficult to fabricate, which was explained in terms of a thermodynamic driving force to form single-phase oxide. The well-structured control that can be obtained using magnetron sputtering will be fully exploited in the coming years while considering a definitive dependence of the superficial structure in the photocatalytic process[17].Montmorillonite-TiO 2 nanocomposites using during the photodegradation of 1,2,4trichlorobenzene are also presented. Both ultrasonic and stirring methods were used to synthesize the samples, while a complete characterization approach provided relevant results about the chemical, morphological and structural properties of the catalysts as well as the photo handling charges and mechanism pathway[18].…”