Douglas R. MacFarlane

University of Wollongong, City of Greater Wollongong, New South Wales, Australia

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Publications (300)1122.6 Total impact

  • Mega Kar, Tristan J Simons, Maria Forsyth, Douglas R MacFarlane
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    ABSTRACT: Metal-air batteries are a well-established technology that can offer high energy densities, low cost and environmental responsibility. Despite these favourable characteristics and utilisation of oxygen as the cathode reactant, these devices have been limited to primary applications, due to a number of problems that occur when the cell is recharged, including electrolyte loss and poor efficiency. Overcoming these obstacles is essential to creating a rechargeable metal-air battery that can be utilised for efficiently capturing renewable energy. Despite the first metal-air battery being created over 100 years ago, the emergence of reactive metals such as lithium has reinvigorated interest in this field. However the reactivity of some of these metals has generated a number of different philosophies regarding the electrolyte of the metal-air battery. Whilst much is already known about the anode and cathode processes in aqueous and organic electrolytes, the shortcomings of these electrolytes (i.e. volatility, instability, flammability etc.) have led some of the metal-air battery community to study room temperature ionic liquids (RTILs) as non-volatile, highly stable electrolytes that have the potential to support rechargeable metal-air battery processes. In this perspective, we discuss how some of these initial studies have demonstrated the capabilities of RTILs as metal-air battery electrolytes. We will also show that much of the long-held mechanistic knowledge of the oxygen electrode processes might not be applicable in RTIL based electrolytes, allowing for creative new solutions to the traditional irreversibility of the oxygen reduction reaction. Our understanding of key factors such as the effect of catalyst chemistry and surface structure, proton activity and interfacial reactions is still in its infancy in these novel electrolytes. In this perspective we highlight the key areas that need the attention of electrochemists and battery engineers, in order to progress the understanding of the physical and electrochemical processes in RTILs as electrolytes for the various forms of rechargeable metal-air batteries.
    Physical Chemistry Chemical Physics 08/2014; · 3.83 Impact Factor
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    ABSTRACT: Using permeation through a model membrane in a Franz diffusion cell, we have demonstrated that acidic and basic active pharmaceutical ingredients (APIs) in deep eutectic ‘liquid co-crystal’ form can be held tightly together, even in solution, via strong hydrogen bonds or partially ionized interactions, providing simultaneous transport at rates much higher than solutions of their corresponding, commercially available crystalline salts, albeit at rates that are lower than the neutral forms of the individual molecules. It was also shown that the deep eutectic APIs do not have to be premade, but hydrogen-bonded complexes can be formed in situ by mixing the corresponding API–solvent solutions. To understand the behavior, we have extensively studied a range of nonstoichiometric mixtures of lidocaine and ibuprofen spectroscopically and via membrane transport. The data demonstrates the nature of the interactions between the acid and base and provides a route to tune the rate of membrane transport.
    Chemical Science 07/2014; 5(9). · 8.31 Impact Factor
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    ABSTRACT: The fate of [MnIII/IV2(μ-O)2(terpy)2(H2O)2]3+ (1) under conditions typically applied to test its ability to catalyze water oxidation was studied by X-ray absorption spectroscopy and UV/Vis spectrophotometry by using [MnIII/IV2(μ-O)2(bipy)4]3+(2) and Mn2+ as controls (terpy=2,2′:6′,2“-terpyridine, bipy=2,2′-bipyridine). The sample matrix, pH and choice of oxidizing agent were found to have a significant effect on the species formed under catalytic conditions. At low range pH values (4–6), homogeneous catalysis testing in oxone implied that 1 remains intact, whereas in clay intercalate there is strong evidence that 1 breaks down to a birnessite-like phase. In homogeneous solutions at higher pH, the results are consistent with the same birnessite-like structure identified in the clay intercalate. The use of the molecular complexes, as a source of manganese instead of simple MnII salts, was found to have the effect of slowing down oxide formation and particle aggregation in solution. The original analytical results that implied the systems are molecular are discussed in the context of these new observations.
    ChemCatChem 06/2014; · 5.18 Impact Factor
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    ABSTRACT: The physicochemical properties of a range of NaNTf2 (or NaTFSI) salt concentrations in N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (or C3mpyrFSI) ionic liquid were investigated by DSC, conductivity, cyclic voltammetry and diffusivity studies. Cyclic voltammetry indicated a stable sodium plating behavior with a current of 5 mA cm(-2) at 25 °C to 20 mA cm(-2) at 100 °C, along with high reversibility identifying this electrolyte as a possible candidate for sodium-ion or sodium metal battery applications. (23)Na NMR chemical shifts and spectral linewidths (FWHM) indicate a complex coordination of the Na(+) ion which is dependent on both temperature and salt concentration with an apparently stronger coordination to the NTf2 anion upon increasing the NaNTf2 concentration. Temperature dependent PFG-NMR diffusion measurements show that both FSI and NTf2 have a comparable behaviour although the smaller FSI anion is more diffusive.
    Physical Chemistry Chemical Physics 05/2014; · 3.83 Impact Factor
  • Mega Kar, Bjorn Winther-Jensen, Maria Forsyth, Douglas R Macfarlane
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    ABSTRACT: The coordination of zinc ions by tetraglyme has been investigated here to support the development of novel electrolytes for rechargeable zinc batteries. Zn(2+) reduction is electrochemically reversible from tetraglyme. The spectroscopic data, molar conductivity and thermal behavior as a function of zinc composition, between mole ratios [80 : 20] and [50 : 50] [tetraglyme : zinc chloride], all suggest that strong interactions take place between chloro-zinc complexes and tetraglyme. Varying the concentration of zinc chloride produces a range of zinc-chloro species (ZnClx)(2-x) in solution, which hinder full interaction between the zinc ion and tetraglyme. Both the [70 : 30] and [50 : 50] mixtures are promising electrolyte candidates for reversible zinc batteries, such as the zinc-air device.
    Physical Chemistry Chemical Physics 04/2014; · 3.83 Impact Factor
  • Jinpeng Han, Guiyin Xu, Bing Ding, Jin Pan, Hui Dou, Douglas R. MacFarlane
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    ABSTRACT: Porous nitrogen-doped hollow carbon spheres (PNHCS) had been prepared by pyrolysis of hollow polyaniline spheres (HPS), which were synthesized by the use of sulfonated polystyrene spheres (SPS) as a hard template. PNHCS have a specific surface area of 213 m2 g−1 and a pore volume of 0.24 cm3 g−1. At a current density of 0.5 A g−1, the specific capacitance of the PNHCS prepared is ca. 213 F g−1. The capacity retention after 5000 charge/discharge cycles at a current density of 1 A g−1 is more than 91%. The enhanced electrochemical performance can be attributed to the unique carbon nanostructure and nitrogen-doping of the PNHCS electrodes. The hollow macro-structure plays the role of an “ion-buffering” reservoir. The micropores of the PNHCS enlarge the specific surface area, while the mesopores offer larger channels for liquid electrolyte penetration. Nitrogen groups in the PNHCS not only improve the wettability of the carbon surface, but also enhance the capacitance by addition of a pseudocapacitive redox process.
    J. Mater. Chem. A. 03/2014; 2(15).
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    ABSTRACT: Knowledge of the proton transport behaviour in electrolyte materials is crucial for designing and developing novel solid electrolytes for electrochemical device applications such as fuel cells or batteries. In the present work, high proton conductivity (approximately 10-3 S cm-1) was observed in the triflic acid (HTf) containing guanidinium triflate (GTf) composites. The proton transport mechanism in the composite was elucidated by comparing the diffusion coefficients obtained from NMR and conductivity measurements. Several orders of magnitude enhancement of conductivity is observed upon addition of HTf to the organic solid, and this appears to follow percolation behaviour with a percolation threshold of approximately 2% HTf. The data support a structural diffusion (or Grotthuss) mechanism of proton transport with a calculated Haven ratio significantly less than unity. 13C SUPER and 14N overtone NMR experiments were used to study the mobility and symmetry of the triflate anion and guanidinium cation respectively at a molecular level. The former experiment shows that the CF3 group in the anion displays fast and isotropic motion at room temperature. In contrast to the high mobility of the anion group, the 14N overtone experiments indicate that the guanidinium cation is static in both the pure and the acid-containing GTf samples at room temperature. It is anticipated that these solid-state NMR techniques may be also applied to other organic solid state electrolyte materials to achieve a better understanding of their transport mechanisms and molecular dynamics.
    Journal of Materials Chemistry A. 01/2014; 2(3):681-691.
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    ABSTRACT: We report the morphogenesis and self-assembly of bismutite nanocrystals with fully tunable morphologies from square plates, octagonal sheets, and round disks into three-dimensional hierarchical nanostructures. The results show that the nucleation, growth and self-assembly of bismutite nanocrystals strongly depend on the synergistic effect between hydroxide and citrate ions. The three-dimensional hierarchical nanostructures are formed through an oriented-attachment of bismutite nanocrystals along the 〈001〉 directions. The bismutite hierarchical nanostructures can be utilized for efficient and selective adsorption and separation. A novel surface-enhanced Raman spectroscopy platform based on a bismutite/gold nanoparticles core–shell structure has been developed for ultrasensitive detection of aromatic molecules with a detection limit down to 1 nM.
    Journal of Materials Chemistry 01/2014; 2(7):2275-2282. · 5.97 Impact Factor
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    ABSTRACT: The oxygen reduction reaction (ORR) in the presence of proton donors of similar proton activities (water, methanol and ethylene glycol), as well as weak and strong acids has been studied in a phosphonium-based IL, [P66614][Cl].[P66614][Cl]/ethylene glycol mixtures showed better ORR performance than mixtures containing water or methanol in terms of onset potential and current density. This enhancement in performance similar to that produced by weak acids, is attributed to the self-stabilization of ethylene glycol after proton removal; this has been corroborated by calculation of the hydrogen-bond donating ability. Interestingly under these conditions, the oxygen reduction reaction on a glassy carbon electrode follows an overall 4-electron pathway (i.e., two 2-electron processes) which is of importance in the performance of air cathodes in electrochemical devices.
    Electrochemistry Communications 01/2014; 38:24–27. · 4.29 Impact Factor
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    ABSTRACT: Vitrification of sugar-based solutions plays an important role incryopreservation, lyophilization, and the emerging field of anhydrous preservation. An understanding of the glass transitioncharacteristics of such formulations is essential for determiningan appropriate storage temperature to ensure an extended shelf life of vitrified products. To better understand the effect of saltson the glass transition temperature (Tg) ofglass-forming sugars, we investigated severaldata-fitting models (Fox, Gordon-Taylor and Kwei) for sugar-saltformulations using data from the literature, as well as new data generated on blends of trehalose and choline dihydrogen phosphate (CDHP). CDHP has recently been shown to have promise as a stabilizing agent for proteins and DNA. The Kwei equation, which has a specific parameter characterizing intermolecular interactions, providesgood fits to the Tg data for sugar-salt blends, and complements other commonly used models that are frequently used to model Tg data.
    Cryobiology 12/2013; · 2.14 Impact Factor
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    ABSTRACT: Thermoelectrochemical cells (TECs) have the potential to offer a continuous renewable electricity supply from a variety of thermal energy sources. Because of the thermal gradient, the device characteristics are a complex function of temperature dependent electrolyte transport properties, electrode electro-catalytic properties and the Seebeck coefficient of the redox couple. Understanding the interplay between these functions is critical to identifying the limiting factors that need to be overcome to produce more advanced devices. Thus, in this work we have developed a theoretical model for TECs and have measured a range of properties required by the model. We focused attention on the Co(n)(bpy)3(NTf2)n in a [C2mim][B(CN)4] ionic liquid electrolyte as one of the optimal systems for >100 °C operation. The exchange current densities on a range of electrode materials were measured in order to explore the role of electrode function in the simulation. Alternatives to platinum electrodes (maximum output power, Pmax = 183 mW m(-2)), including platinized stainless steel, Pt-SS (Pmax = 188 mW m(-2)) and poly(3,4-ethylenedioxythiophene) deposited on stainless steel, PEDOT-SS (Pmax = 179 mW m(-2)), were shown to be viable options. From the simulations we conclude that for further development of ionic liquid TECs, modifications to the redox couple to increase the Seebeck coefficient, and increasing the rate of diffusion of the redox couple to minimize mass transport resistance, will yield the greatest improvements in device performance.
    Physical Chemistry Chemical Physics 12/2013; · 3.83 Impact Factor
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    ABSTRACT: Electronic Supplementary Information (ESI) available: Analytical techniques, NMR purification data, density, viscosity, DSC data, SEM imaging, Ionogel rheometry and Vibrational spectroscopy results.
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    ABSTRACT: The physicochemical properties of free-standing cross-linked poly(N-isopropylacrylamide) (pNIPAAM) gels, generated in the presence of the Ionic liquids (ILs), 1-ethyl-3-methylimidazolium [C2mIm](+) salts of ethylsulfate [EtSO4](-), dicyanamide [DCA](-), bis(trifluoromethylsulfonyl)imide [NTf2](-), and trihexyltetradecylphosphonium dicyanamide ([P6,6,6,14][DCA]) are described. The Lower Critical Solution Temperature (LCST) of the resulting ionogel was found to vary between 24-31 °C. The behaviour of swelling is found to be as high as 31.55% (±0.47, n = 3) from the initial dehydrated state, while 28.04% (±0.42, n = 3) shrinking from the hydrated swollen state is observed. For ionogels based on the [DCA](-) anion an unexpected complete loss of the shrinking behaviour occurs, attributed to water interactions with the nitrile group of the [DCA](-) anion. Scanning Electron Microscopy also reveals distinct morphological changes, for example [C2mIm][EtSO4] displays a highly porous, nodule type morphology, efficiently pre-disposed for water uptake.
    Physical Chemistry Chemical Physics 12/2013; · 3.83 Impact Factor
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    ABSTRACT: This paper presents an extended study on the ion effects of a series of biocompatible hydrated choline based ionic liquids (ILs) on lactate oxidase (LOx), an important enzyme in biosensing technology for the in vitro detection of lactic acid. Secondary structural analysis revealed changes in the protein conformation in hydrated ILs, while thermal unfolding/aggregation dynamics showed different profiles in the presence or absence of ILs. Moreover, LOx thermally denaturised at 90 °C showed residual activity in the presence of chloride and dihydrogen phosphate anions. Kinetic and lifetime studies were also performed, providing a better understanding of the ion effects of ILs on the biocatalytic activity of the enzyme.
    Physical Chemistry Chemical Physics 12/2013; · 3.83 Impact Factor
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    ABSTRACT: A series of sulfonate based copolymer ionomers based on a combination of ionic liquid and sodium cations have been prepared in different ratios. This system was designed to improve the ionic conductivity of ionomers by partially replacing sodium cations with bulky cations that are less associated with anion centres on the polymer backbone. This provides more conduction sites for sodium to ‘hop’ to in the ionomers. Characterization showed the glass transition and 15N chemical shift of the ionomers did not vary significantly as the amount of Na+ varied, while the ionic conductivity increased with decreasing Na+ content, indicating conductivity is increasingly decoupled from Tg. Optical microscope images showed phase separation in all compositions, which indicated the samples were inhomogeneous. The introduction of low molecular weight plasticizer (PEG) reduced the Tg and increased the ionic conductivity significantly. The inclusion of PEG also led to a more homogeneous material.
    J. Mater. Chem. A. 12/2013; 2(2).
  • A. F. Halima, Usman Ali Rana, Douglas R. MacFarlane
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    ABSTRACT: Silicon has potential application as a functional semiconductor electrode in proposed solar water split- ting cells. It is abundant and has excellent photovoltaic attributes, however it is extremely susceptible to corrosion, even in the dark, resulting in the formation of an electrochemically passive oxide upon inter- action with aqueous media. This work investigates the potential for conductive, inert and transparent boron doped diamond (BDD) coatings to protect p-type Silicon (p-Si). The stability and electrochemical performance of p-Si and p-Si|BDD were investigated using voltammetric techniques in 1 M H2 SO4 , before and after long-term exposure to the acidic medium (up to 280 hours) under no applied potential bias. Unprotected Si degraded very rapidly whilst BDD was shown to protect the underlying Si, as evident from I-V curves that indicated no increased resistance across the Si-diamond interface. Furthermore, BDD supported facile proton reduction at significantly lower onset potential for the hydrogen evolution reaction (up to -500 mV vs. SCE) compared with bare Si cathode (-850 mV vs. SCE). The activity of the BDD electrode/electrolyte interface was further improved by coating with platinum catalyst particles, to produce a p-Si|BDD|Pt structure, which reduced the HER onset to nearly zero overpotential. Tafel analysis indicated that desirable electrochemical activity and stability were achieved for p-Si|BDD|Pt, making this a promising electrode for application in water splitting cells
    Electrochimica Acta 11/2013; 115:639-643. · 4.09 Impact Factor
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    ABSTRACT: The use of ionic liquids as additives to base oil for the lubrication of steel on aluminium was investigated. The miscibility and wear performance of various phosphonium, imidazolium and pyrrolidinium ionic liquids in a range of polar and non-polar base oils was determined. The structure and ion pairing of the ionic liquids was found to be important in determining their miscibility in the base oils. In wear tests, some of the miscible base oil/IL blends reduced the aluminium wear depth when compared to that found with the base oil alone. The non-polar base oil/IL blends were able to withstand higher wear-test loads than the polar base oil/IL blends. At 10 N, as little as 0.01 mol/kg of IL, or 0.7-0.9 wt.%, in the non-polar base oils was enough to drastically reduce the wear depth on the aluminium. XPS analysis of the wear surfaces suggested that the adsorbing of the IL to the surface, where it can form low-shear layers and also react to form tribofilms, is important in reducing friction and wear. The largest reductions in wear at the highest load tested were found for a mineral oil/P6,6,6,14 i(C8)2PO2 blend.
    ACS Applied Materials & Interfaces 11/2013; · 5.01 Impact Factor
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    ABSTRACT: A series of multifunctional protic ionic liquids (PILs), some of which are based on a combination of primary and tertiary amines in the same moiety coupled with a carboxylic acid, have been synthesised and employed for CO2 capture, yielding absorption capacities comparable to standard absorbents. In contrast to traditional amine absorbers, CO2 was found to desorb at lower temperatures and hence could result in a significant reduction in both the energy required to strip the absorber of CO2 and the thermally activated degradation mechanisms, which in traditional absorbers result in the loss of absorber and the production of toxic compounds. The lower basicity of the amine sites resultant from PIL formation decreases the binding energy of the CO2 to the absorber. The weaker basicity is also evidenced by lower pH of the PIL CO2 absorbers, which reduces common corrosion problems associated with traditional amine absorbers.
    Physical Chemistry Chemical Physics 10/2013; · 3.83 Impact Factor
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    ABSTRACT: An extensive study of interaction energies in ion pairs of pyrrolidinium and imidazolium ionic liquids is presented. The Cnmpyr and Cnmim cations with varying alkyl chains from Methyl, Ethyl, n-Propyl to n-Butyl were combined with a wide range of routinely used IL anions such as chloride, bromide, mesylate (CH3SO3 or Mes), tosylate (CH3PhSO3 or Tos), bis(trifluoromethanesulfonyl)amide (NTf2), dicyanamide (N(CN)2 or dca), tetrafluoroborate (BF4) and hexafluorophosphate (PF6). A number of energetically favourable conformations were studied for each cation-anion combination. The interaction energy and its dispersion component of the single ion pairs were calculated using a sophisticated state-of-the-art approach: a second-order of Symmetry Adapted Perturbation Theory (SAPT). A comparison of energetics depending on the cation-anion type, as well as the mode of interaction was performed. Dispersion forces were confirmed to be of importance for the overall stabilisation of ionic liquids contributing from 28 kJ mol(-1) in pyrrolidinium ion pairs to 59 kJ mol(-1) in imidazolium ion pairs. The previously proposed ratio of total interaction energy to dispersion components and melting points was assessed for this set of ionic liquids and was found to correlate with their melting points for the anionic series, producing separate trends for the Cnmim and Cmpyr series of cations. Chlorides, bromides and tetrafluoroborates formed close-to-ideal correlations when both types of cations, Cnmim and Cnmpyr, were combined in the same trend. Correlation of the dispersion component of the interaction energy with transport properties such as conductivity and viscosity was also considered. For imidazolium-based ionic liquids strong linear correlations were obtained, whereas pyrrolidinium ionic liquids appeared to be insensitive to this correlation.
    Physical Chemistry Chemical Physics 10/2013; · 3.83 Impact Factor
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    ABSTRACT: Energy storage worth its salt: A series of protic salts are synthesized and their thermal properties characterized; the guanidinium triflate and mesylate salts exhibit high heats of fusion (ΔH f), which indicates their promising role in energy storage applications, particularly in the temperature range of 100–200 °C.
    Energy Technology. 10/2013; 1(10).

Publication Stats

2k Citations
1,122.60 Total Impact Points

Institutions

  • 2014
    • University of Wollongong
      • ARC Centre of Excellence for Electromaterials Science
      City of Greater Wollongong, New South Wales, Australia
  • 1986–2014
    • Monash University (Australia)
      • • Department of Materials Engineering, Clayton
      • • School of Chemistry, Clayton
      Melbourne, Victoria, Australia
  • 2013
    • University of Leipzig
      • Wilhelm Ostwald Institut of Physical and Theoretical Chemistry
      Leipzig, Saxony, Germany
  • 2009–2013
    • University of North Carolina at Charlotte
      • Department of Mechanical Engineering and Engineering Science
      Charlotte, NC, United States
  • 2008–2013
    • Dublin City University
      • • School of Chemical Sciences
      • • Biomedical Diagnostics Institute
      Dublin, L, Ireland
    • University of Leicester
      Leiscester, England, United Kingdom
  • 2012
    • Deakin University
      • Institute for Frontier Materials (IFM)
      Geelong, Victoria, Australia
  • 2004–2012
    • Monash University (Malaysia)
      Labuan, Labuan, Malaysia
  • 2011
    • Vienna University of Technology
      • Institute of Applied Synthetic Chemistry
      Vienna, Vienna, Austria
  • 2007–2011
    • Tokyo University of Agriculture and Technology
      • Division of Biotechnology and Life Science
      Edo, Tōkyō, Japan
  • 1993
    • Macquarie University
      Sydney, New South Wales, Australia