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Photocatalysts for hydrogen 10

generation and organic

contaminants degradation

†
*
Rupali Nagar , Eswaraiah Varrla , Bhaghavathi P. Vinayan ‡,§
⁎ Symbiosis International University, Pune, India, SRM University, Chennai, India,
†
§
‡ Helmholtz Institute Ulm (HIU), Ulm, Germany, Karlsruhe Institute of Technology (KIT),
Karlsruhe, Germany
10.1 Introduction

The combined presence of hydrogen and oxygen in the form of water sustains life on
Earth. Nature maintains a balance between various ecological systems; however, these
systems are being disturbed by human activities. Rockstrӧm and colleagues discuss
nine Earth-system processes and define a safe operating space for the nine planetary
systems [1]. Table 10.1 shows the planetary boundaries’ proposed limits and draws
a comparison between the preindustrial values and the values up to the past decade.
Three of the nine boundaries (i.e., climate change, the biodiversity loss rate, and the
nitrogen cycle) are believed to have been crossed already and thus require our atten-
tion in order for the course to be corrected [1]. An important step toward meeting the
world’s energy demands will be to replace fossil-based fuels with green and renewable
energy sources.
The other step in this direction is to restore the freshwater ecosystem. The Earth’s
surface is about 75% water. About 96.5% of the water on the Earth’s surface exists in
the form of oceans, seas, or bays, followed by 1.74% in the form of ice caps, glaciers,
and permanent snow and 1.7% as ground water; the remaining 0.06% includes mois-
ture, biological forms, and so on [2,3]. Fig. 10.1 depicts the distribution of water on
Earth, which suggests that a very limited amount is usable for household, agricultural,
and industrial activities. Thus it is very important to conserve freshwater resources
and curb their pollution levels. One of the sources of water contamination is the waste-
water from industries that contain dyes. Dyes carry carcinogens that pose a threat to
aquatic life and human life and that disturb the ecological balance. Decontaminating
water and making it free of organic impurities could prove to be another effective step
in this regard [4]. These two subjects are the main focus of this chapter, i.e., photo-
catalytic hydrogen production and organic contaminant degradation, both of which
involve water. The former is discussed in Section 10.2 and the latter in Section 10.3.
For achieving these targets, we need to understand the chemical reactions, to engineer
materials to carry out the desired reactions, and to integrate them into processes such
as water splitting, water decontamination systems, and so on.

Multifunctional Photocatalytic Materials for Energy. https://doi.org/10.1016/B978-0-08-101977-1.00011-9
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