Abstract
One of the key features of a nano catalyst for photocatalysis is the band gap, because, through its analysis, the potential of the catalyst can be determined. In this investigation, the impact on the band gap of different catalysts made by the sol–gel method, compared with TiO2 P25 Sigma-Aldrich, showing the effect of using gold or ruthenium as a metal supported on TiO2, with two different dosage percentages of 1 and 3 percent, was analysed. Additionally, two oxidation states of the catalyst, the reduced form and the oxidized form of the metal, were used to see the effect on the band gap. The experiments show that the gold addition has a higher beneficial effect on the band gap for the UV region (ultra violet region), and the ruthenium addition has a higher beneficial effect for the UV/visible region. The preferred oxidation state for the band gap was the oxidized state. The characterisation of the catalyst provided an insight into the relation between the band gap and the catalyst itself.
Highlights
Photocatalysis is a process of great interest because, in recent years, it has been shown to have wide applications in environmental decontamination processes because it can degrade a wide variety of organic compounds like sugars [1]
The TiO2 semiconductor is normally used as a catalyst by absorbing light of different wavelengths owing to their electronic structure, characterized by an empty conduction band and with a filled valence band [3]
X-ray diffraction (XRD) was performed to determine the crystallinity of the elements that are present in the catalyst
Summary
Photocatalysis is a process of great interest because, in recent years, it has been shown to have wide applications in environmental decontamination processes because it can degrade a wide variety of organic compounds like sugars [1]. Heterogeneous photocatalytic solar oxidation consists of using near-solar UV radiation (wavelength less than 380 nm; energy levels larger than 3.2 eV) to photo-excite a semiconductor catalyst in the presence of oxygen Under these circumstances, the oxidation of the pollutants takes place. The photocatalytic process takes place from the irradiation of light with sufficient energy to equal or exceed the band-gap of the semiconductor, causing the excitation of an electron from the valence band (VB) to the conduction band (CB) [3] In this way, electron–hole pairs (e− /h+ ) are created that can migrate to the surface of the catalyst, being trapped in superficial sites and reacting with the adsorbed species [4]. The voids (empty states) that form in the valence band of the solid react with electron-donating species, such as water molecules or hydroxyl ions attached to the surface of Processes 2020, 8, 1032; doi:10.3390/pr8091032 www.mdpi.com/journal/processes
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