Chapter 1
Mechanism of Photocatalysis
1.1 Introduction
Environmental pollution is becoming a big challenge for the new developing and
developed world because of the industrial revolution, which on the one side is
facilitating the life but on the other side destroying the environment. The chemical,
textile, oil, and gas industries annually send billion of tons of hazardous effluents to
the groundwater and upper environment which is affecting badly the marine life,
human, and plant kingdom [1–3]. At present, there are a number of technologies that
have been discovered to cater the fast-growing problem; the most commonly
employed method of removing pollutants involves the use of various physical
techniques, chemical and biological processes, and thermal techniques to remove
commonly found organic and inorganic contaminants [4, 5]. Among many proposed
processes being developed for the decontamination of the organic-based pollutants,
biodegradation received the greatest attention. However, numerous organic
chemicals, especially those which are toxic or refractory, were found very resistant
to the biological degradation [6, 7]. Therefore, after the discovery of photocatalytic
splitting of water by Fujishima and Honda [8] in 1972, the researchers turned their
point of convergence toward semiconductor photocatalysis which proved very
effective in the degradation of even those pollutants which are highly difficult to
remove by the other means. In comparison with the traditional oxidation process, the
photocatalysis has significant advantages, for example, they can be used to degrade
and mineralize the dyes and chemicals completely to CO 2 and H 2 O and are also
helpful in the degradation of very stable compounds which cannot be easily
degraded by the other processes, also they can work efficiently at ambient temperature and pressure conditions, and they do not need any special supply of oxygen.
The other advantage of the photocatalysis is that it is a cheap process as compared to
the other oxidation process having no waste disposal problems [3]. A large number
of semiconductor photocatalysts have been investigated so far for the degradation of
different pollutants, such as ZnO [9, 10], WO 3 [11, 12], Fe 2 O 3 [13], CdSe [14], and
© Springer Nature Singapore Pte Ltd. 2018
J. Zhang et al., Photocatalysis, Lecture Notes in Chemistry 100,
https://doi.org/10.1007/978-981-13-2113-9_1
1
Mechanism of Photocatalysis
1.1 Introduction
Environmental pollution is becoming a big challenge for the new developing and
developed world because of the industrial revolution, which on the one side is
facilitating the life but on the other side destroying the environment. The chemical,
textile, oil, and gas industries annually send billion of tons of hazardous effluents to
the groundwater and upper environment which is affecting badly the marine life,
human, and plant kingdom [1–3]. At present, there are a number of technologies that
have been discovered to cater the fast-growing problem; the most commonly
employed method of removing pollutants involves the use of various physical
techniques, chemical and biological processes, and thermal techniques to remove
commonly found organic and inorganic contaminants [4, 5]. Among many proposed
processes being developed for the decontamination of the organic-based pollutants,
biodegradation received the greatest attention. However, numerous organic
chemicals, especially those which are toxic or refractory, were found very resistant
to the biological degradation [6, 7]. Therefore, after the discovery of photocatalytic
splitting of water by Fujishima and Honda [8] in 1972, the researchers turned their
point of convergence toward semiconductor photocatalysis which proved very
effective in the degradation of even those pollutants which are highly difficult to
remove by the other means. In comparison with the traditional oxidation process, the
photocatalysis has significant advantages, for example, they can be used to degrade
and mineralize the dyes and chemicals completely to CO 2 and H 2 O and are also
helpful in the degradation of very stable compounds which cannot be easily
degraded by the other processes, also they can work efficiently at ambient temperature and pressure conditions, and they do not need any special supply of oxygen.
The other advantage of the photocatalysis is that it is a cheap process as compared to
the other oxidation process having no waste disposal problems [3]. A large number
of semiconductor photocatalysts have been investigated so far for the degradation of
different pollutants, such as ZnO [9, 10], WO 3 [11, 12], Fe 2 O 3 [13], CdSe [14], and
© Springer Nature Singapore Pte Ltd. 2018
J. Zhang et al., Photocatalysis, Lecture Notes in Chemistry 100,
https://doi.org/10.1007/978-981-13-2113-9_1
1