[Show abstract][Hide abstract] ABSTRACT: The electrochemical performance of asymmetric supercapacitors (ASCs) using MWCNTs/NiS and graphene nanoplatelets as positive and negative electrode, respectively, are reported. Nickel sulfide nanoparticles can be decorated on multiwall carbon nanotubes using a hydrothermal synthesis process, with graphene nanoplatelets obtained via a chemical route. The fabricated ACSs were operated over a potential window of 1.4 V with a specific capacitance of 181 F g -1 observed at 1 A g -1 . The ASCs were cycled at 2 A g -1 showing 92% retention of initial capacitance after 1000 cycles. .
[Show abstract][Hide abstract] ABSTRACT: A novel alkaline exchange ionomer (AEI) was prepared from the radiation-grafting of vinylbenzyl chloride
(VBC) onto poly(ethylene-co-tetraﬂuoroethylene) [ETFE] powders with powder particle sizes of less than
100 mm diameter. Quaternisation of the VBC grafted ETFE powders with trimethylamine resulted in AEIs
that were chemically the same as the ETFE-based radiation-grafted alkaline anion exchange membranes
(AAEM) that had been previously developed for use in low temperature alkaline polymer electrolyte fuel
cells (APEFC). The integration of the AEI powders into the catalyst layers (CL) of both electrodes resulted
in a H2/O2 fuel cell peak power density of 240 mW cm�2 at 50 C (compared to 180 mW cm�2 with a
benchmark membrane electrode assembly containing identical components apart from the use of a
previous generation AEI). This result is promising considering the wholly un-optimised nature of the AEI
inclusion into the catalyst layers.
Journal of Materials Chemistry A: Materials for Energy and Sustainability 02/2014; 2:5124 - 5130.
[Show abstract][Hide abstract] ABSTRACT: Nanostructured thin films of vanadium oxides were deposited using electric field assisted chemical vapour deposition. The films were characterised using scanning electron microscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. It was found that the films had open and porous morphologies with extremely small (5 nm) surface features. The films were made into supercapacitor cells and tested using cyclic voltammetry. It was found that stable asymptotic values specific capacitance values as high as 3700 [small mu ]F cm-2 could be obtained with good cycling behaviour. Electrodes synthesized in this way show promise for applications in fields such as supercapacitors.
Journal of Materials Chemistry 01/2014; · 5.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mediator-less, direct electro-catalytic reduction of oxygen to water by bilirubin oxidase (Myrothecium sp.) was obtained on anthracene-modified, multi-walled carbon nanotubes. H2O2 was found to significantly and irreversibly affect the electro-catalytic activity of bilirubin oxidase, whereas similar electrodes comprised of laccase (Trametes versicolor) were reversibly inhibited.
Chemical Communications 01/2014; 50:94-96. · 6.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The relationship between the diversity of mixed-species microbial consortia and their electrogenic potential in the anodes of microbial fuel cells was examined using different diversity measures as predictors. Identical microbial fuel cells were sampled at multiple time-points. Biofilm and suspension communities were analysed by denaturing gradient gel electrophoresis to calculate the number and relative abundance of species. Shannon and Simpson indices and richness were examined for association with power using bivariate and multiple linear regression, with biofilm DNA as an additional variable. In simple bivariate regressions, the correlation of Shannon diversity of the biofilm and power is stronger (r = 0.65, p = 0.001) than between power and richness (r = 0.39, p = 0.076), or between power and the Simpson index (r = 0.5, p = 0.018). Using Shannon diversity and biofilm DNA as predictors of power, a regression model can be constructed (r = 0.73, p < 0.001). Ecological parameters such as the Shannon index are predictive of the electrogenic potential of microbial communities.
[Show abstract][Hide abstract] ABSTRACT: Palladium-Nickel (Pd-Ni) hollow nanoparticles were synthesized via a modified galvanic replacement method using Ni nanoparticles as sacrificial templates in an aqueous medium. X-ray diffraction and transmission electron microscopy show that the as-synthesized nanoparticles are alloyed nanostructures and have hollow interiors with an average particle size of 30 nm and shell thickness of 5 nm. Compared with the commercially available Pt/C or Pd/C catalysts, the synthesized PdNi/C has superior electrocatalytic performance towards the oxygen reduction reaction, which makes it a promising electrocatalyst for alkaline anion exchange membrane fuel cells and alkali-based air-batteries. The electrocatalyst is finally examined in an H2/O2 alkaline anion exchange membrane fuel cell; the results show that such electrocatalysts could work in a real fuel cell application as a more efficient catalyst than state-of-the-art commercially available Pt/C.
[Show abstract][Hide abstract] ABSTRACT: Hydrogen peroxide production by glucose oxidase (GOx) and its negative effect on laccase performance have been studied. Simultaneously, FAD-dependent glucose dehydrogenase (FAD-GDH), an O2-insensitive enzyme, has been evaluated as a substitute. Experiments focused on determining the effect of the side reaction of GOx between its natural electron acceptor O2 (consumed) and hydrogen peroxide (produced) in the electrolyte. Firstly, oxygen consumption was investigated by both GOx and FAD-GDH in the presence of substrate. Relatively high electrocatalytic currents were obtained with both enzymes. O2 consumption was observed with immobilized GOx only, whilst O2 concentration remained stable for the FAD-GDH. Dissolved oxygen depletion effects on laccase electrode performances were investigated with both an oxidizing and a reducing electrode immersed in a single compartment. In the presence of glucose, dramatic decreases in cathodic currents were recorded when laccase electrodes were combined with a GOx-based electrode only. Furthermore, it appeared that the major loss of performance of the cathode was due to the increase of H2O2 concentration in the bulk solution induced laccase inhibition. 24 h stability experiments suggest that the use of O2-insensitive FAD-GDH as to obviate in situ peroxide production by GOx is effective. Open-circuit potentials of 0.66 ± 0.03 V and power densities of 122.2 ± 5.8 μW cm(-2) were observed for FAD-GDH/laccase biofuel cells.
Physical Chemistry Chemical Physics 10/2013; 15:19371-19379. · 4.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Birnessite nanotubes and activated carbon electrodes have been used in supercapacitor cells to assess the performance of new aqueous based electrolyte systems at temperatures as low as -30 °C. The addition of ethylene glycol to aqueous sodium, lithium, potassium and ammonium sulfates has resulted in electrolytes that are still in liquid phase at such low temperatures. Extensive electrochemical testing showed that in such systems, operation of these aqueous based supercapacitors is possible at -30 °C with a specific capacitance of over 30 F g(-1) and good cycleability.
Physical Chemistry Chemical Physics 02/2013; · 4.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Birnessite MnO2 nanotubes of high specific surface area have been used as one electrode material in supercapacitors with a commercial-carbon-based second electrode ((NH4)2SO4(aq.) electrolyte). Assembled cells have been subjected to full electrochemical testing at temperatures [less-than-or-equal]80 [degree]C. At elevated temperatures, specific capacitance as high as 700 F g-1 has been observed. The increase in specific capacitance with temperature has been found to be at a cost to cycling performance. Furthermore, the time spent at elevated temperatures "at rest" has been shown to have a major effect on device lifetime. It has been found that at 80 [degree]C, without cycling, such devices lose all significant capacitance after 21 days. The findings herein are believed to have major implications for transport, storage lifetime and ultimate utilization of such systems.
Journal of Materials Chemistry 01/2013; 1(45):14140-14146. · 5.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A glucose oxidase (GOd) bioelectrode exhibiting high performance, direct electron transfer (DET) has been prepared. Unprecedented redox peak current densities of 1 mA cm(-2) were observed alongside a clear electrochemical response to glucose. This system shows potential as a low cost, high performance enzymatic bioelectrode.
Physical Chemistry Chemical Physics 06/2012; 14(27):9582-5. · 4.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The performance and dynamics of the bacterial communities in the biofilm and suspended culture in the anode chamber of sucrose-fed microbial fuel cells (MFCs) were studied by using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified partial 16S rRNA genes followed by species identification by sequencing. The power density of MFCs was correlated to the relative proportions of species obtained from DGGE analysis in order to detect bacterial species or taxonomic classes with important functional role in electricity production. Although replicate MFCs showed similarity in performance, cluster analysis of DGGE profiles revealed differences in the evolution of bacterial communities between replicate MFCs. No correlation was found between the proportion trends of specific species and the enhancement of power output. However, in all MFCs, putative exoelectrogenic denitrifiers and sulphate-reducers accounted for approximately 24% of the bacterial biofilm community at the end of the study. Pareto-Lorenz evenness distribution curves extracted from the DGGE patterns obtained from time course samples indicated community structures where shifts between functionally similar species occur, as observed within the predominant fermentative bacteria. These results suggest the presence of functional redundancy within the anodic communities, a probable indication that stable MFC performance can be maintained in changing environmental conditions. The capability of bacteria to adapt to electricity generation might be present among a wide range of bacteria.
Applied Microbiology and Biotechnology 01/2012; 93(1):423-37. · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The spatiotemporal development of a bacterial community in an exoelectrogenic biofilm was investigated in sucrose-fed longitudinal tubular microbial fuel cell reactors, consisting of two serially connected modules. The proportional changes in the microbial community composition were assessed by polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE) and DNA sequencing in order to relate them to the performance and stability of the bioelectrochemical system. The reproducibility of duplicated reactors, evaluated by cluster analysis and Jaccard's coefficient, shows 80-90% similarity in species composition. Biofilm development through fed-batch start-up and subsequent stable continuous operation results in a population shift from γ-Proteobacteria- and Bacteroidetes- to Firmicutes-dominated communities, with other diverse species present at much lower relative proportions. DGGE patterns were analysed by range-weighted richness (Rr) and Pareto-Lorenz evenness distribution curves to investigate the evolution of the bacterial community. The first modules shifted from dominance by species closely related to Bacteroides graminisolvens, Raoultella ornithinolytica and Klebsiella sp. BM21 at the start of continuous-mode operation to a community dominated by Paludibacter propionicigenes-, Lactococcus sp.-, Pantoea agglomerans- and Klebsiella oxytoca-related species with stable power generation (6.0 W/m(3)) at day 97. Operational strategies that consider the dynamics of the population will provide useful parameters for evaluating system performance in the practical application of microbial fuel cells.
Applied Microbiology and Biotechnology 03/2011; 90(3):1179-91. · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Birnessite nanotubes have been made through a templated hydrothermal route. Variations in experimental conditions have resulted in differing morphologies of high specific surface area. After forming into electrodes in supercapacitor test cells, good cycleability was observed with specific capacitances approaching 350 F g−1 at low discharge current densities.
Energy & Environmental Science 01/2011; 4(8):2813-2817. · 11.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A simple aqueous-processable alkaline ionomer (amenable to scale-up) has been developed for enhancing electrode/electrolyte interfaces in clean energy devices (e.g. alkaline polymer electrolyte membranefuelcells). The water uptake of the alkaline ionomer is tuneable allowing its use as a tool for fundamental studies into these interfaces.
Energy & Environmental Science 01/2011; 4(12):4925-4928. · 11.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper we report the successful incorporation of sulfate and phosphate into SrCoO3 leading to a change from a 2H- to a 3C-perovskite polymorph. Structural characterization by neutron diffraction showed extra weak peaks related to oxygen vacancy ordering, and these could be indexed on an expanded tetragonal cell, containing two inequivalent Co sites, similar to previously reported for Sb doped SrCoO3. Conductivity measurements on the doped systems showed a large enhancement compared to the undoped hexagonal system, consistent with corner-sharing of CoO6 octahedra for the former. Further work on the doped samples shows, however, that they are metastable, transforming back to the hexagonal cell on annealing at intermediate temperatures. The incorporation of Fe was shown, however, to improve the stability at intermediate temperatures, and these co-doped phases also showed high conductivities.
Journal of Solid State Chemistry 01/2011; 184(11):2972-2977. · 2.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A controlled interfacial synthesis using a permeable membrane has been used to obtain ε-MnO2 of a globular morphology, with a mechanism of formation inferred from SEM results. Specific surface areas of 50–160 m2 g−1 have been obtained through simple variation of the permeable membrane used in synthesis. This has been shown to have a marked effect on both particle size and pore size distributions. After assembly in supercapacitor test cells with aqueous neutral electrolyte, specific capacitances have been determined through galvanostatic cycling giving initial values as high as 240 F g−1, which drop to 160 F g−1 after 200 cycles at low discharge rates. Excellent cycling behavior is observed at higher discharge rates.
Journal of Materials Chemistry 04/2010; 20(16):3221-3226. · 5.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Synthesis and characterisation of nanostructured vanadium oxide based systems and their application in energy storage devices, namely supercapacitors, is presented. Vanadium oxide has been synthesised using a hydrothermal route in presence of various templates. X-ray diffraction studies reveal the formation of vanadium (IV) oxide as majority phase. SEM and TEM results depict presence of different nano-structured morphologies depending upon the template used. BET surface area measurement shows an increase of ∼7 times in the surface area of the synthesised powders in comparison to surface area of the starting raw powders. Conductivity enhancement of ∼3 to 5 orders of magnitude is observed as compared to conductivity of the starting raw material. These properties make this templated system suitable for application as electrode material in energy storage devices such as supercapacitors. Promising results of charge discharge on supercapacitors assembled using templated vanadium oxide based electrodes are reported. It is proposed that such systems can act as a cheap alternative to RuO<sub align="right"> 2 </sub>.
International Journal of Nanotechnology 01/2010; 7(9-12):861-869. · 1.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Varying thicknesses of ethylene-co-tetrafluoroethylene (ETFE) Alkaline Anion Exchange Membranes (AAEMs) with quaternary ammonium functional groups were prepared using e-beam irradiation. The performances in H2/O2 single cell fuel cells were tested at 50 °C with the thinnest AAEM (S20) achieving the highest peak power density of 230 mW cm− 2. The ability to use non-Pt electrocatalysts for the oxygen reduction reaction (ORR) at the cathode was also investigated.
Solid State Ionics 01/2010; 181:219-222. · 2.05 Impact Factor