Preparation of PteNiO/Co
3
O
4
nanocompounds based counter
electrodes from PteNi/Co alloys for high efficient dye-sensitized solar
cells
Zhang Lan
*
, Lanfang Que, Wanxia Wu, Jihuai Wu
Engineering Research Center of Environment-Friendly Functional Materials, Ministry of Education, Key Laboratory of Functional Materials for Fujian Higher
Education, Institute of Materials Physical Chemistry, Huaqiao University, Xiamen 361021, China
article info
Article history:
Received 25 May 2015
Accepted 11 June 2015
Available online 12 June 2015
Keywords:
Dye-sensitized solar cell
Counter electrode
Platinumenickel/cobalt oxide
Photovoltaic performance
abstract
Platinumenickel/cobalt oxide (PteNiO/Co
3
O
4
) nanocompounds with size about 30e50 nm are synthe-
sized for preparing counter electrodes (CEs) by in-situ oxidation of PteNi/Co alloys through thermal
treatment in air. Electrochemical activity measurements including cyclic voltammetry, electrochemical
impedance spectroscopy, and Tafel polarization indicate that PteNiO/Co
3
O
4
CEs have highly catalytic
activity for reduction of triiodide to iodide and low charge transfer resistance at the electrolyte/electrode
interface. The DSSCs with PteNiO/Co
3
O
4
CEs show high power conversion efficiency exceeding 8%.
Especially, the DSSC with PteNiO CE achieves a comparative power conversion efficiency of 9.48% versus
the DSSC with thermal decomposited Pt CE (9.42%) under full sunlight illumination.
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
Dye-sensitized solar cells (DSSCs) have been extensively
researched as a new kind of solar cells [1,2]. A typical DSSC com-
poses a conductive substrate, a dye-sensitized wide bandgap
semiconductor thin film, a liquid redox contained electrolyte, and a
counter electrode (CE). Platinum (Pt) is a conventional catalyst used
in CE to catalyze the reduction of triiodide (I
3
-
) to iodide (I
) in the
electrolyte [3]. Even though Pt offers superior catalytic activity,
numerous studies have been made with the aim of decreasing the
used amount of Pt or with other substitutes since it is a kind of
noble metals [4].
There are two approaches to prepare low cost CEs. One way is
using Pt-free catalytic materials including carbon [5,6], conductive
polymer [7,8], metal chalcogenide [9,10], and so on; the other way
is applying Pt-contained composites such as Pt-carbon [11,12], Pt-
conductive polymer [13,14], Pt-metal or metal oxide composites
[15e17]. Among them, Pt-metal alloys show highly catalytic activity
in reducing I
3
to I
, and DSSCs with this kind of CEs can attain to
high power conversion efficiency (PCE) [18]. However, the I
3
/I
contained liquid electrolyte is highly corrosive for most of metals,
especially when the parameter of these metals is in nanoscale,
which will potentially change the composition of metals or alloys
and further decrease the stability of DSSCs. Compared with Pt-
metal alloys, Pt-metal oxide composites show obviously higher
stability in the I
3
/I
contained liquid electrolyte because of the
lower corrosion of I
3
/I
for metal oxides [19].
Here, platinumenickel/cobalt oxide (PteNiO/Co
3
O
4
) nano-
compounds are synthesized for preparing CEs by in-situ oxidation
of PteNi/Co alloys through thermal treatment in air. The methods
show some advantages. Firstly, PteNiO/Co
3
O
4
nanocompounds
have higher corrosion resistant than their alloys counterparts in the
I
3
/I
contained liquid electrolyte. Secondly, with high temperature
thermal treatment, organic components adsorbed on the surface of
PteNiO/Co
3
O
4
nanocompounds can be totally burned out. Thirdly,
PteNiO/Co
3
O
4
nanocompounds can be sintered on FTO glasses
firmly by the thermal treatment. The prepared PteNiO/Co
3
O
4
nanocompounds based CEs show highly catalytic activity in DSSCs,
and PCE of the DSSCs can attain to high values exceeding 8%.
2. Experimental section
2.1. Materials
The reagents including H
2
PtCl
6
$6H
2
O, Ni(NO
3
)
2
$6H
2
O, Co(N-
O
3
)
2
$6H
2
O, octadecyl amine (ODA), ethanol, toluene, cyclohexane,
and nitric acid were analytical grade and used without further
purification(Sinopharm Chemical Reagent Co., Ltd, China). Fluorine
* Corresponding author.
E-mail address: lanzhang@hqu.edu.cn (Z. Lan).
Contents lists available at ScienceDirect
Journal of Alloy s and Compounds
journal homepage: http://www.elsevier.com/locate/jalcom
http://dx.doi.org/10.1016/j.jallcom.2015.06.088
0925-8388/© 2015 Elsevier B.V. All rights reserved.
Journal of Alloys and Compounds 646 (2015) 80e85