Chapter 1 - An overview of synthesis techniques for preparing doped photocatalysts

Abstract

Fossil fuels are the mainstay of most technologies in fashion currently, and their excessive use is also the primary reason for many of the environmental problems that are being encountered (Marschall & Wang, 2014). One major renewable energy technology is photocatalysis, which requires only solar radiation for energy production by artificial photosynthetic reactions and can degrade environmental pollutants to less harmful fractions (Khaki et al., 2017; Ong et al., 2016). An extensively practiced way for efficient photocatalyst construction is the doping of the crystal lattice of the native semiconductor by a metal or nonmetal ions. Doping introduces defects into the ideal crystal lattice of the native semiconductor and also improves the activity of the photocatalysts by modifying their electronic structures (Shao et al., 2018). Such defects can entrap electrons or holes formed during the photoexcitation process. Another important function of the defect sites like vacancies is to increase the catalytic activation of strong bonds kinetically facilitating reactions. Doping could also lead to additional charge carriers in the photocatalyst and form extra bands that may narrow or widen the original bandgap. Therefore, doping can affect light absorption, reduce recombination through trap sites, and alter VB or CB positions to change the photocatalytic activity towards a substrate molecule or reaction. The present chapter gives a concise review of the synthesis techniques used to produce doped WBG semiconductors. The method of preparation of doped semiconductors determines the amount of doping possible and the nanostructure formed. It is important to mention that only those research works which report shift in XRD peaks of the original phase due to doping have been discussed in this chapter.