3.1.2. Characterization

along the C axis as showed in Figure 8a, b. The photocatalytic activity is due to [Bi2O2] layers intercalated of double halogen atoms that allow a better separation of the electron-hole pairs. The bismuth oxychloride (BiOCl) is a solid inorganic compound, not toxic, of pearlescent white color and due its brightness has been used in the cosmetic industry. There is a record not greater than 500 articles reported in the Scopus database concerning the use of BiOCl, as photocatalyst; this review was realized in June 2018 (Figure 8c) and the first publications

Figure 8. Scheme of unit cell (a), crystal structure BiOCl with {001} facet (b) and growing of articles of BiOCl in the

The BiOCl has a bandgap of 3.2–3.5 eV and the valence band is constituted of O2p and Cl3p; while the conduction band has Bi6p according to density functional theory (DFT), whereby

Most studies of BiOCl photocatalyst are focused on enhancing the photocatalytic activity for environmental remediation, especially for dyes degradation during water treatment. Due to the bandgap, its photocatalytic activity, under UV irradiation, has shown a similar or better photocatalytic activity than TiO2 [35]. Some "model" dyes used to evaluate the photocatalytic activity with BiOCl are methylene blue, methyl orange [36], and Rh B [37]. In spite of the bandgap of BiOCl, there are reports wherein demonstrate an excellent degradation of RhB

However, some challenges remain for BiOCl as most photocatalysts also face; one challenge is its activation under visible light due to the limited absorption of such radiation. A variety of strategies have been employed to get better light absorption and to decrease the charge carrier recombination, such as the heterojunction, doping impurity, and metallization of the surface. Modifications consider the presence of metal elements or compounds like Ag [39, 40], AgCl [41], Fe [42], and Bi [43], also with materials carbon-based as graphene [44], graphene oxide [45], and with other semiconductors as Co3O4 [46], BiOI [47], and TiO2 [48–50]. However, most researches evaluated the photocatalytic activity for degradation of dyes, considering the RhB in many cases. Other pollutant photodegradation studies are bisphenol A using Fe-BiOCl under visible light [42], sulfanilamide with BiOCl-RGO [51], and phenol under visible light with BiOCl-TiO2 composite [50]. Nowadays, the BiOCl is being investigated to reduce of carbon dioxide (CO2) [52].

when excited, the electrons from Cl atoms are displaced at bismuth orbital [34].

appeared in 2007 with a growing interest during the last years.

under visible light [38].

photocatalytic process in later years (c).

70 Photocatalysts - Applications and Attributes

The crystal structure of the synthesized photocatalysts was analyzed by X-ray diffraction (XRD) using a DX8 advance diffractometer (Bruker) with: Cu Kα radiation, 35 kV, 25 mA, λ = 0.15418 nm over the 2θ range of 10–80 in a step of 0.02s 1 . The analysis of surface morphology and microstructure of the samples was carried out by a QUANTA 200 environmental scanning electron microscope.
