Nanoporous gold–copper oxide based all-solid-
state micro-supercapacitors†
Balwant Kr Singh, Aasiya Shaikh, Subramanya Badrayyana, Debananda Mohapatra,
Rajiv O. Dusane and Smrutiranjan Parida
*
The rapid growth of miniaturized electronic devices has increased the demand for energy storage devices
with small dimensions. Micro-supercapacitors have great potential to supplement or replace batteries and
electrolytic capacitors for a wide range of applications. Micro-supercapacitor can be fabricated with micro-
electronic devices for efficient energy storage unit. However, the lower energy densities of micro-
supercapacitors are still a bigger challenge to its application in micro devices. In this paper, we report
all-solid-state nanoporous gold (NPG)–copper oxide (CuO) based micro-supercapacitor prepared using
a simple fabrication process. In this process, first NPG interdigital patterns were developed by using
a simple annealing and dealloying procedure, and then CuO was electrodeposited on NPG interdigital
microelectrodes. The nanoporous gold substrate provides good electronic/ionic conductivity with
high intrinsic surface area for the electrodeposition of CuO, which forms a novel hybrid electrode. The
NPG–CuO micro-supercapacitor exhibits maximum areal capacitance 26 mF cm
2
, maximum specific
energy 3.6 mW h cm
2
and maximum specific power 646 mW cm
2
. NPG–CuO micro-supercapacitors
show excellent cyclic stability with 98% capacitance retention after 10 000 cycles.
1. Introduction
Miniaturization of portable micro-electronics devices and
microelectromechanical systems (MEMS) has increased the
demand of small scale energy storage systems that can be inte-
grated on an electronic chip. As the size of individual devices get
smaller, the power consumption also decreases to a reasonably
low level.
1,2
Presently most of microdevices are powered by
rechargeable microbatteries, but the microbatteries are limited by
their cycle life, low power density and abrupt failure.
3
On the
other hand supercapacitor is an energy storage device with high
power density, fast charge and discharge time, and long service
life.
4,5
As conventional sandwich supercapacitor design is
incompatible with microdevices, new supercapacitor design with
interdigital pattern has developed to reduce the size and enhance
charge transfer characteristics.
6
Miniaturized supercapacitors or
micro-supercapacitor can be fabricated with microelectronic
devices to work as efficient energy storage units.
5,7
Development
of microelectronic fabrication technology has enabled us to
integrate on-chip interdigital planner micro-supercapacitor for
high energy and high power delivery.
7
The performance of micro-supercapacitor depends on
intrinsic property of electrode materials, electrolyte and
architectural design of device and fabrication process.
7,8
In
literature to increase the energy density and the power density
of interdigital planner micro-supercapacitor with a gra-
phene,
9,10
activated carbon,
11,12
onion-like carbon,
13
and
photoresist derived carbon
14,15
have been investigated and are
capable of delivering high power density while their energy
density (0.1–1.0 mW h cm
3
)
16
and operation time are not
sufficient to meet microdevices requirements. To achieve the
high energy density micro-supercapacitor with transition
metal oxides (RuO
2
/carbon nanowalls,
17
tubular RuO
2
,
18
MnO
2
,
19
MnO
x
/Au,
20
VN–NiO,
21
MWCNT/V
2
O
5
,
22
CoO/CNT
23
etc.) has been also developed, but most of transition metal
oxide suffer from poor electrical conductivity except RuO
2
.
Application of RuO
2
micro-supercapacitor is limited due to its
high cost. Among transition metal oxides, CuO is a promising
candidate because of its lower cost, larger abundance, non-
toxicity, environmental stability and desirable electro-
chemical properties. The theoretical capacitance of CuO is
nearly 1800 F g
1
, which is comparable with theoretical
capacitance of most widely used pseudocapacitance material
MnO
2
(1370 F g
1
) and hydrated ruthenium oxide (RuO
2
-
$nH
2
O) (2200 F g
1
).
24,25
The available literature on CuO as
electrode material for supercapacitor suggest that they suffer
from lower electrical conductivity due to the method of
synthesis followed.
19,26–30
Compared to other methods of
synthesis of CuO, electrodeposition
16,31,32
demonstrate
multiple benets such as mass control, excellent conductivity
and precise control of the oxidation.
Department of Metallurgical Engineering and Materials Science, Indian Institute of
Technology-Bombay, Powai, Mumbai – 400076, Maharashtra, India. E-mail:
paridasm@iitb.ac.in; Tel: +91-22-2576-7643
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c6ra19744b
Cite this: RSC Adv. , 2016, 6, 100467
Received 4th August 2016
Accepted 15th October 2016
DOI: 10.1039/c6ra19744b
www.rsc.org/advances
This journal is © The Royal Society of Chemistry 2016 RSC Adv. , 2016, 6, 100467–100475 | 100467
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