Advanced three-component ZnO/Ag/CdS nanocomposite photoanode
for photocatalytic water splitting
Xiaoli Zhang
a
, Yang Li
b
, Junliang Zhao
c
, Shuguo Wang
a
, Yongdan Li
b
, Haitao Dai
a
,
*
,
Xiaowei Sun
d
a
School of Science, Tianjin University, Tianjin 300072, China
b
School of Chemical Engineering, Tianjin University, Tianjin 300072, China
c
Shanghai Juntech Co. Ltd., 1378 Xingxian Road, Shanghai 201815, China
d
School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, 639798 Singapore, Singapore
highlights
Ag nanoparticles as co-catalysts were introduced into the interface of ZnO/CdS.
The three-component anode modified with Ag nanoparticles showed improved hydrogen evolution and corrosion resistance.
Ag nanoparticles can greatly enhance light absorption and charge carriers transport of photoanode.
The effects of Ag loading on the advanced performance of photoanode can be confirmed by FDTD simulation.
article info
Article history:
Received 24 January 2014
Received in revised form
29 June 2014
Accepted 30 June 2014
Available online 9 July 2014
Keywords:
Photolysis
Ag co-catalyst
Photostability
Hydrogen generation
abstract
In this work, Ag nanoparticles as co-catalysts are employed to modify the nanoscale ZnO/CdS interface to
achieve a ZnO/Ag/CdS nanocomposite photoanode for photocatalytic water splitting. The three-
component photoanode exhibits signi fi cantly enhanced photoelectrochemical properties as compared
with the single-component (ZnO) and two-component (ZnO/Ag or ZnO/ CdS) systems. The modification
with Ag nanoparticles can significantly enhance the light absorption and facilitate the separation and
transport of photogenerated carr iers through the localized surface plasma resonance (LPSR) effect. The
developed ZnO/Ag/CdS nanocomposite photoanode presents significantly improved water splitting
performance, with a high hydrogen productivity up to 3.5 mL h
1
(~155 umol h
1
)atþ 0.4 V vs. Ag/AgCl
electrode with an almost constant rate during 10 h. Even without any external bias, the photoanode can
still exhibit a relatively high hydrogen productivity up to 0.5 mL h
1
. Furthermore, the nanocomposite
photoanode shows excellent photocorrosion resistance, which is ascribed to a considerable decrease of
surface defect density on ZnO nanowires and the reduction of holes.
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
Collecting and storing solar energy in chemical bonds, as nature
accomplishes through photosynthesis, is a highly desirable
approach to solve the energy challenge. One way of solar energy
conversion and storage is the photocatalytic water splitting using
semiconductors as both the light absorber and energy converter, to
store solar energy in the simplest chemical bond, H
2
[1,2].Itiswell
known that the high energy conversion efficiency requires that the
photoelectrode materials effectively harvest the sunlight, facilitate
a rapid charge transport and exhibit a long-term stability [3,4].
However, most of the developed semiconductors for water splitting
have a wide band gap and are only sensitive to the UV portion of
sunlight (~5% of the whole sunlight spectrum), resulting in the
limited light absorption in the visible region and overall low pho-
toelectric conversion efficiency [5]. To resolve this problem, a nar-
rower band gap sensitizer coating is considered as one promising
way to extend the absorption of sunlight to the visible region.
Recently, ZnO nanowires based core/shell architectures have been
fabricated by overlying deposition of narrow band gap organic dyes
[6], inorganic quantum dots [7] and polymeric absorbers [8].
Among these sensitizing materials, CdS was used as a visible light
photocatalyst for water splitting due to its narrow direct band gap
(2.4 eV) and flat band potential at 0.66 V (PH 7) [9]. However, CdS
* Corresponding author. Tel.: þ86 22 2740 4118; fax: þ86 22 2740 3425.
E-mail addresses: htdai@tju.edu.cn (H. Dai), exwsun@ntu.edu.sg (X. Sun).
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Journal of Power Sources
journal homepage: www.elsevier.com/locate/jpowsour
http://dx.doi.org/10.1016/j.jpowsour.2014.06.165
0378-7753/© 2014 Elsevier B.V. All rights reserved.
Journal of Power Sources 269 (2014) 466e 472