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Vidhyadharan B.,Nanostructured Renewable Energy Materials Laboratory | Misnon I.I.,Nanostructured Renewable Energy Materials Laboratory | Aziz R.A.,Nanostructured Renewable Energy Materials Laboratory | Padmasree K.P.,CINVESTAV | And 2 more authors.
Journal of Materials Chemistry A | Year: 2014

Copper oxide (CuO) nanowires of diameter ∼30-50 nm were developed by an aqueous polymeric solution based electrospinning process and their structural, morphological, and electrochemical properties were studied with the aim to fabricate high performance supercapacitor devices. The wires consist of densely packed cuboidal particles of size ∼10 nm characterized by a low degree of crystal defects. Supercapacitor electrodes were fabricated on nickel foam substrates using 75 wt% CuO in 15 wt% conducting carbon and 10 wt% polyvinylidene fluoride. The supercapacitive properties of the electrodes were evaluated in a three-electrode configuration in aqueous electrolytes, viz. KOH and LiOH, employing cyclic voltammetry (CV), charge-discharge cycling (CDC) and electrochemical impedance spectroscopy (EIS). A record specific capacitance (CS) is observed for the present electrospun CuO nanowires: C S ∼ 620 F g-1 in KOH and 581 F g-1 in LiOH at a current density of 2 A g-1 with a Coulombic efficiency of ∼100%. Compared with the previous results on the electrochemical stability of CuO nanostructures, the material electrospun using an aqueous polymeric solution showed a much higher operational stability (98% at the end of 1000 cycles and 92% at the end of 2000 cycles) owing to its superior crystallinity. The electrochemical properties of the electrodes were determined using EIS to validate the CV and CDC results. This journal is © the Partner Organisations 2014.

Fakharuddin A.,Nanostructured Renewable Energy Materials Laboratory | Ahmed I.,Nanostructured Renewable Energy Materials Laboratory | Wali Q.,Nanostructured Renewable Energy Materials Laboratory | bin Khalidin Z.,Universiti Malaysia Pahang | And 2 more authors.
Advanced Materials Research | Year: 2014

A number of nanocrystalline, mesoporous large area (~0.2- 2 cm2) dye-sensitized solar cells (DSSCs) are probed by electrochemical impedance spectroscopy measurements to realize their carrier dynamics such as charge transport resistance (RCT), electron diffusion coefficient (Dη), and electron lifetime (τn) by applying an equivalent electrical model. The experimental upshots reveal that the electron lifetime relates with the device physical parameters which was neglected in previous studies. It is also found that the RCT relates negatively with the device area i.e. it decrease upon increasing photo-exposed area. The observed lowering of current density (JSC) over a series of experiments upon increasing the photoelectrode area is attributed to the decrease in RCT. The charge carriers upon injection into semiconductor layer find increased diffusion pathways and eventually recombine with the hole species when characterized by lower carrier lifetime. The thickness of the electrode film does not play an effective role indicating that the dynamics of larger area DSSCs differs largely from those of a single cell. The experimental results available indicate that a nearly complete collection of charge carriers is possible in large area modules provided the physical dimensions of photoelectrode area are considered. The results from the study hints future directions to build high efficiency DSSC modules and further asserts considering the diffusion length in twodimensions while fabricating larger area cells. © (2014) Trans Tech Publications, Switzerland.

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