Applied Catalysis A: General 409–410 (2011) 215–222
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Applied Catalysis A: General
j ourna l ho me page: www.elsevier.com/locate/apcata
Enhanced visible light photocatalytic activity of novel polymeric g-C
3
N
4
loaded
with Ag nanoparticles
Lei Ge
∗
, Changcun Han, Jing Liu, Yunfeng Li
Department of Materials Science and Engineering, College of Science, China University of Petroleum Beijing, Beijing 102249, PR China
a r t i c l e i n f o
Article history:
Received 30 August 2011
Received in revised form 1 October 2011
Accepted 4 October 2011
Available online 8 October 2011
Keywords:
g-C3N4
Photocatalysis
Functional
Semiconductors
a b s t r a c t
Novel polymeric g-C
3
N
4
photocatalysts loaded with noble metal Ag nanoparticles were prepared via a
facile heating method. The obtained Ag/g-C
3
N
4
composite products were characterized by X-ray diffrac-
tion (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution
transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse
reflection spectra (DRS) and photoluminescence spectra (PL). The photocatalytic activities of Ag/g-C
3
N
4
samples were investigated based on the decomposition of methyl orange and hydrogen evolution under
visible light irradiation. The XPS results revealed that it was the metallic Ag
0
deposited on polymeric
g-C
3
N
4
samples. The Ag/g-C
3
N
4
photocatalysts exhibited significantly enhanced photocatalytic perfor-
mance for the degradation of methyl orange and hydrogen production compared with pure g-C
3
N
4
. The
optimal Ag content was determined to be 1.0 wt%, and the corresponding hydrogen evolution rate was
10.105 mol h
-1
, which exceeded that of pure g-C
3
N
4
by more than 11.7 times. The enhanced photocat-
alytic performance could be attributed to the synergic effect between Ag and g-C
3
N
4
, which promoted
the migration efficiency of photo-generated carriers. The proposed mechanism for the enhanced visi-
ble light photocatalytic activity of g-C
3
N
4
modified by a small amount of Ag was further confirmed by
photoluminescence spectroscopy.
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
Semiconductor-based photocatalysis has attracted extensive
interest since the photo-induced splitting of water on TiO
2
elec-
trodes was discovered [1–3]. Photocatalysis is one of the most
promising technologies for pollutants decomposition and hydro-
gen evolution by the generation of
•
OH radicals and other oxidative
radicals [4–6]. In the past decades, various inorganic materials, such
as oxides, sulfides, and oxynitride have been explored as photo-
catalysts for hydrogen production and environmental purification
under UV or visible light irradiation [7–10]. One of the main goals in
materials science fields is to find photocatalysts with high quantum
efficiency and catalytic performance [11,12]. However, the low-
usage of visible light has restrained the photocatalytic activity of
photocatalysts in the environmental remediation [13]. Therefore, it
is urgent to develop the novel photocatalysts for pollutants degra-
dation, which have appropriate band gap, strong oxidative ability
and high stability in water solution system.
∗
Corresponding author. Tel.: +86 010 89733200; fax: +86 010 89733200.
E-mail address: gelei08@sina.com (L. Ge).
Recently, some semiconductors have been found to be active for
degradation of organic contaminants or splitting of water under
visible light irradiation, such as BiVO
4
[14], Bi
2
WO
6
[15], BiFeO
3
[16], K
10
[Nb
2
O
2
(H
2
O)
2
][SiNb
12
O
40
] [17], CMPs [18], etc. They all
show certain absorption ability in the visible light range. However,
these novel photocatalysts have some disadvantages. Especially,
the photo-generated charge carriers may recombine during the
migration process, leading to the decrease of the photocatalytic
activity. In order to increase the utilization rates of visible light,
numerous methods have been employed to modify the photocata-
lysts, such as doping of metal or nonmetal elements [19], quantum
dots sensitization [20], and coupling with other semiconductors
[21]. Therefore, designing more efficient visible light induced and
high stability photocatalysts, which can meet the requirement of
practical environmental purification, represents the central chal-
lenge of photocatalysis research.
As the most stable allotrope of carbon nitride, graphitic car-
bon nitride (g-C
3
N
4
) has the smallest direct band gap due to
the sp
2
hybridization of carbon and nitrogen forming the -
conjugated graphitic planes [22]. The polymeric g-C
3
N
4
has been
successfully used as metal-free heterogeneous catalysts for Friedel-
Crafts reactions and the chemical binding and reduction of CO
2
0926-860X/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.apcata.2011.10.006