Chapter 13
Syntheses and Applications of Silver
Halide-Based Photocatalysts
13.1 Introduction
In the past decades, photocatalysis has received increasing attention for its potential
to solve worldwide energy crisis (water splitting [1–4] and solar cell [5–7]), environmental pollution (water and air purification [8–12], and pathogen inactivation
[13–15]), and greenhouse effect (CO 2 conversion [16–19]). Among various
photocatalytic materials, TiO 2 has been the most widely researched for its excellent
properties, such as high photocatalytic activity, low cost, high stability, and
nontoxicity [20–24]. However, its two defects, no response to visible light and
low photo-quantum efficiency, seriously limit its practical application. Hence, to
full use of solar energy, the development of visible light-driven photocatalytic
materials has become the most significant topic in the photocatalytic field.
Silver halide (AgX), a kind of well-known photographic material, was developed
in 1839 with the daguerreotype [25, 26]. The photographic process in AgX is as
follows: after absorbing a photon, silver halide can produce an electron and a hole,
and subsequently the electron combines with an interstitial silver ion to form an Ag
0
atom [27, 28]. Upon repeated absorption of photons, a cluster of silver atoms (latent
image) will be formed ultimately [29, 30]. Due to the instability under light, silver
halides are seldom used as photocatalysts previously.
In 1996, the photocatalytic activity of AgX was firstly reported by Calzaferri et al.
[31]. During the photocatalytic reaction, the photo-generated electron–hole pairs will
react with sacrificial agent and water to evolve O 2 or H 2 . In this period, the Ag
nanoparticles formed on the surface of AgX were seen as electron trappers, which
can capture photo-generated electrons by Schottky barrier between Ag and AgX.
Therefore, the formation of Ag nanoparticles can not only enhance the
photocatalytic activity of AgX by separating carriers but also improve the stability
of AgX by decreasing the amount of electrons in AgX [32]. In 2008, Huang et al.
[33] found that the Ag nanoparticles on AgX can also enhance the absorption of
visible light by surface plasma resonance (SPR) effect, which triggered an upsurge
© 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_13
307
Syntheses and Applications of Silver
Halide-Based Photocatalysts
13.1 Introduction
In the past decades, photocatalysis has received increasing attention for its potential
to solve worldwide energy crisis (water splitting [1–4] and solar cell [5–7]), environmental pollution (water and air purification [8–12], and pathogen inactivation
[13–15]), and greenhouse effect (CO 2 conversion [16–19]). Among various
photocatalytic materials, TiO 2 has been the most widely researched for its excellent
properties, such as high photocatalytic activity, low cost, high stability, and
nontoxicity [20–24]. However, its two defects, no response to visible light and
low photo-quantum efficiency, seriously limit its practical application. Hence, to
full use of solar energy, the development of visible light-driven photocatalytic
materials has become the most significant topic in the photocatalytic field.
Silver halide (AgX), a kind of well-known photographic material, was developed
in 1839 with the daguerreotype [25, 26]. The photographic process in AgX is as
follows: after absorbing a photon, silver halide can produce an electron and a hole,
and subsequently the electron combines with an interstitial silver ion to form an Ag
0
atom [27, 28]. Upon repeated absorption of photons, a cluster of silver atoms (latent
image) will be formed ultimately [29, 30]. Due to the instability under light, silver
halides are seldom used as photocatalysts previously.
In 1996, the photocatalytic activity of AgX was firstly reported by Calzaferri et al.
[31]. During the photocatalytic reaction, the photo-generated electron–hole pairs will
react with sacrificial agent and water to evolve O 2 or H 2 . In this period, the Ag
nanoparticles formed on the surface of AgX were seen as electron trappers, which
can capture photo-generated electrons by Schottky barrier between Ag and AgX.
Therefore, the formation of Ag nanoparticles can not only enhance the
photocatalytic activity of AgX by separating carriers but also improve the stability
of AgX by decreasing the amount of electrons in AgX [32]. In 2008, Huang et al.
[33] found that the Ag nanoparticles on AgX can also enhance the absorption of
visible light by surface plasma resonance (SPR) effect, which triggered an upsurge
© 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_13
307