Environmental Engineering Reference
In-Depth Information
12
Semiconductor nanomaterialS for organic
dye degradation and Hydrogen Production
via PHotocatalySiS
Leticia M. Torres-Martínez, Isaías Juárez-Ramírez, and Mayra Z. Figueroa-Torres
Departamento de Ecomateriales y Energía, Facultad de Ingeniería Civil-Universidad Autónoma de Nuevo León,
Avenida Universidad y Avenida Fidel Velázquez S/N, Ciudad Universitaria, San Nicolás de los Garza,
Nuevo León, México
12.1
introduction
The combination of nanotechnology and photocatalysis for clean environment and for providing a renewable energy source has
been one of the most important research subjects in recent years. In particular, photocatalytic processes using semiconductor
materials in nanoparticle size have been demonstrated to be effective technologies for organic compound degradation and
hydrogen production from water splitting. The interest is because in these photocatalytic processes, solar energy can be used as
a primary energy source to activate the semiconductor material used as catalyst. It is well known that the photocatalytic process
is carried out through the activation of a semiconductor material with ultraviolet (UV) or visible light irradiation [1, 2].
The photocatalytic process involves the generation of electron-hole pairs in the valence and conduction bands of the
semiconductor. However, the recombination reaction of electrons and holes commonly tends to occur quickly, diminishing the
semiconductor activity [3-9]. Therefore, an electron acceptor added to the reaction mixture is adequate. Hence, it is necessary
to carry out modifications of electronic structure, crystal structure, or physicochemical properties in order to enhance the
activity of semiconductor materials [10, 11]. In recent years, several chemical methods such as hydrothermal, solvo-combustion,
sol-gel, and coprecipitation have been employed to synthesize new and better semiconductor materials with strict control of
composition, homogeneity, size and particle shape, as well as use low temperature for their synthesis.
Particularly, during the past decade, several semiconductor nanomaterials with specific structural, physicochemical, and
electronic characteristics have been designed and prepared in our laboratory for use as active materials in photoinduced
processes. These catalysts could present better photocatalytic performance than TiO 2 , due to the different methods of prepara-
tion like sol-gel, hydrothermal, colloidal, coprecipitation, and mechanical milling. Additionally, the presence of metal transition
cations as dopant agents modifies the band gap value in order to activate the catalysts under UV and visible light irradiation.
Therefore, in this chapter several ceramic semiconductor nanomaterials corresponding to the following binary and ternary
oxides families are presented: (i) perovskite-type structure, for example, NaTaO 3 , La : NaTaO 3 , and Sm : NaTaO 3 ; (ii) pyro-
chlore-type structure, for example, Sm 2 MTaO 7 (M = Fe, In, Ga) and Bi 2 MTa0 7 (M = Fe, In, Ga); (iii) rectangular tunnel-type
structure, for example, Na 2 Ti 6 O 13 ; and (iv) SiC-TiO 2 compounds. These materials have been tested as catalysts for the photo-
degradation of methylene blue, rhodamine B, and indigo carmine under UV or visible light source, as well as a catalyst for
hydrogen production from water splitting under UV light [12-23]. The main research activities of our group focus on both the
performance-structure aspects and the effects of the synthesis route.
 
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