Abstract
Ag2O/TiO2 heterojunctions were prepared by a simple method, i.e., the grinding of argentous oxide with six different titania photocatalysts. The physicochemical properties of the obtained photocatalysts were characterized by diffuse-reflectance spectroscopy (DRS), X-ray powder diffraction (XRD) and scanning transmission electron microscopy (STEM) with an energy dispersive X-ray spectroscopy (EDS). The photocatalytic activity was investigated for the oxidative decomposition of acetic acid and methanol dehydrogenation under UV/vis irradiation and for the oxidative decomposition of phenol and 2-propanol under vis irradiation. Antimicrobial properties were tested for bacteria (Escherichia coli) and fungi (Candida albicans and Penicillium chrysogenum) under UV and vis irradiation and in the dark. Enhanced activity was observed under UV/vis (with synergism for fine anatase-containing samples) and vis irradiation for almost all samples. This suggests a hindered recombination of charge carriers by p-n heterojunction or Z-scheme mechanisms under UV irradiation and photo-excited electron transfer from Ag2O to TiO2 under vis irradiation. Improved antimicrobial properties were achieved, especially under vis irradiation, probably due to electrostatic attractions between the negative surface of microorganisms and the positively charged Ag2O.
Highlights
The application potential of semiconductor photocatalysis, related to environmental remediation and renewable energy processes [1], has been gaining importance in environmentally clean and future technologies [2,3,4]
Ag2O/TiO2 composites were prepared by the physical mixing of Ag2O and TiO2 powders in an agate mortar, i.e., the titania sample was mixed with Ag2O to prepare composites containing 1 wt% of Ag2O (5, 10, and 50 wt% were tested for some reactions)
Ag2O was detected in all coupled samples (Table 1 and Figure 2), and its content varied depending on the titania used
Summary
The application potential of semiconductor photocatalysis, related to environmental remediation and renewable energy processes [1], has been gaining importance in environmentally clean and future technologies [2,3,4]. Titanium(IV) oxide (TiO2, titania) is an n-type semiconductor of great importance for applied photocatalysis [5,6,7]. The advantages of this material are an exceptional high photocatalytic efficiency, chemical inertness, long-term stability and photo-corrosion resistance. The current challenge for the development of technologies based on photocatalysis is still the design of TiO2-originated material with high efficiency in both UV and visible light (vis) irradiation. It should be pointed out that titania is inactive in vis range due to its wide bandgap, and quantum yield under UV irradiation is much lower than 100%, due to the recombination of charge carriers (typical for all semiconductors). The design of new photocatalysts based on TiO2 should consider the above mentioned issues [8,9,10,11]
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