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A first-time comparison of carbon-supported Ru@Pt core@shell nanoparticles (NPs) with varying Pt shell coverages (0–3 monolayers, ML), synthesized by two different methods, was carried out. This in...

Proton conducting polymer electrolytes employed in many electrochemical pseudocapacitors are typically based on aqueous systems, which limit the operating potential and temperature range of these energy storage devices. In this study, we developed non-aqueous polymer electrolytes based on protic ionic liquids (PIL). We relied on cationic substitution to obtain proton conducting yet environmentally benign non-fluorinated ionic liquids. By developing binary systems of PILs with different cations, eutectic compositions of PILs with drastically lowered melting points were demonstrated. Through thermal analyses of these binary systems, phase diagrams were constructed which allowed us to obtain eutectic binary PIL mixtures exhibiting a liquidus range from − 70 °C to 150 °C. These eutectic PIL mixtures were incorporated into polymer systems to develop non-aqueous thin film proton-conducting polymer electrolytes for solid pseudocapacitors. The proton conductivity of the eutectic ionic liquids was observed in the polymer electrolyte systems and promoted pseudocapacitive behavior in solid and liquid capacitor cells.

The effects of SiO 2 and TiO 2 nanofillers on a poly(ethylene oxide) (PEO)–1-ethyl-3-methylimidazolium hydrogensulfate (EMIHSO 4 ) electrolyte were studied and compared with respect to ionic conductivity, crystallinity, and dielectric properties over a temperature range from −10 °C to 80 °C. X-ray diffraction and differential scanning calorimetry were used to study the impact of fillers on the structure of the polymer electrolytes. Using an electrochemical capacitor model, impedance (complex capacitance) and dielectric analyses were performed to understand the ionic conduction process with and without fillers in both semi-crystalline and amorphous states. Despite their different nanostructures, both SiO 2 and TiO 2 promoted an amorphous structure in PEO–EMIHSO 4 and increased the ionic conductivity by a factor of two. While in the amorphous phase, the dielectric constant characteristic of the fillers (TiO 2 in this case) contributed to increased conductivity and cell capacitance. Combining complex capacitance and dielectric analyses is an effective approach to study solid electrochemical capacitors and to identify and explain the impact of different fillers on ionic conduction of polymer electrolytes.

Fuel cells are highly efficient and environmentally friendly energy conversion devices that are receiving increasing attention and are steadily moving toward commercialization. Fuel cells deliver electricity and heat, based on the spontaneous electrochemical oxidation of fuels at the anode and the reduction of oxygen at the cathode, without combustion. In many ways, fuel cells are similar to batteries, although they do not require recharging and operate as long as fuel continues to be provided. There are four leading types of fuels reviewed in this chapter, proton exchange membrane fuel cells (PEMFCs) operating on clean hydrogen, direct alcohol (primarily methanol) fuel cells (DAFCs), solid oxide fuel cells (SOFCs), and molten carbonate fuel cells (MCFCs). PEMFCs and DAFCs normally operate at below 100 °C and are targeted primarily for transportation and mobile applications, while SOFCs and MCFCs, which run at temperatures above 600 °C, can run on a wide variety of fuels and are intended mostly for stationary combined heat and power applications. This review is focused primarily on a description of each of these technologies, with an emphasis on the materials used in the electrodes, the electrolyte that separates them, and the current collectors.

The effect of an amorphous SiO2 nano-filler on ionic conductivity and crystallinity of poly(ethylene oxide) (PEO)–1-ethyl-3-methylimidazolium hydrogensulfate (EMIHSO4) electrolyte has been investigated. After addition of the filler, the ionic conductivity of the electrolyte reached 2.15 mS/cm at room temperature, a more than 2-fold increase over the electrolyte without filler. Structural and thermal analyses indicated that incorporation of SiO2 into PEO–EMIHSO4 improved and retained the amorphous phase by impeding PEO crystallization. The SiO2 filler was also found to be effective in facilitating ionic conduction via promoting the dissociation of EMIHSO4. Solid electrochemical double layer capacitor (EDLC) devices, leveraging the PEO–EMIHSO4 electrolyte with SiO2 filler, showed a fast capacitive response at 1 V/s and stable cycle life.

Structural and electrochemical characterizations were performed to evaluate the effect of nano sized SiO2 filler on poly(ethylene oxide) (PEO)-1 ethyl 3 methylimidazolium hydrogensulfate (EMIHSO4) electrolytes. The increase in ionic conductivity in the -10 to +80 ºC temperature range is attributed to an enhanced ionic dissociation as well as a more stable amorphous phase in the polymer electrolyte with SiO2 filler. Electrochemical capacitors using this polymer electrolyte demonstrated a high rate response up to 1 V/s with a time constant of 1 s.

Solid polymer electrolytes containing poly(ethylene oxide) (PEO) and 1‐ethyl‐3‐methylimidazolium hydrogensulfate (EMIHSO 4 ), an ionic liquid, were investigated. Thermal and structural properties of this polymer electrolyte were characterized using DSC, XRD, and FTIR. After addition of EMIHSO 4 , the melting point of PEO decreased by ca. 25 °C. Thermal and structural analyses indicated that the crystallinity of PEO substantially decreased with increasing EMIHSO 4 content. The interaction between ionic liquid and polymer suggested further dissociation of the ionic liquid. Thus, EMIHSO 4 acted as ionic conductor and plasticizer.

Ionic liquid (IL) was investigated as electrolyte in both liquid and solid states for electrochemical capacitors (ECs). 1 Ethyl 3 methylimidazolium hydrogensulfate (EMIHSO4) is a non fluorinated IL; however, it exhibits high resistivity. This issue could be overcome by employing an EMIHSO4 polymer electrolyte. This polymer IL electrolyte had a slightly better performance compared to liquid IL. The EC with polymer IL had a cell voltage window of 1.5 V. High scan rate response up to 1 V/s in cyclic voltammetry and a time constant of 2 s in impedance analyses was obtained.

1-Ethyl-3-methylimidazolium hydrogensulfate (EMIHSO4), an ionic liquid (IL), was investigated as both liquid and solid electrolyte for electrochemical capacitors (ECs). The high resistivity of EMIHSO4 could be overcome by developing a polymer-EMIHSO4 electrolyte. This polymer electrolyte, preferable for environmental and safety reasons, exhibited better performance than liquid EMIHSO4. ECs fabricated using this polymer electrolyte demonstrated a cell voltage window of 0–1.5 V and very stable cycle life. Good high-rate response up to 1 V/s and a time constant of 1 s were observed through cyclic voltammetry and impedance analyses, respectively.

A key requirement for the large-scale commercialization of proton exchange membrane (PEM) fuel cells is to produce highly active, durable catalysts, while minimizing the use of precious noble metals, especially platinum (Pt). Higher utilization of Pt catalyst can be realized by understanding the effect of the carbon support microstructure on the distribution and formation of Pt nanoparticles (NPs) and by optimizing the synthesis method. In this work, Pt NPs were fabricated using a simple alcohol reduction method and then varying the carbon support pore structure and surface properties. The catalysts were then tested for their activity in 1 M C2H5OH + 0.5 M H2SO4 solutions. For Pt NP preparation, either ethanol or butanol were used as the solvent and reductant. The ethanolic or butanolic solution containing H2PtCl6 was then added to the carbon support dispersed in the same solvent at room temperature, and the mixture was heated at the boiling point for 2 hrs. In the case of the ethanol solvent, an aqueous alkaline solution was added to ensure the completion of Pt reduction [1]. However, this step was not used during synthesis when using butanol, due to its higher reducing power. Three types of carbon supports were investigated, Vulcan carbon (VC), Ketjenblack (KB), and colloid-imprinted carbon powders (CICs). The structure and distribution of the Pt NPs were confirmed by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Figure 1 shows the cyclic voltammograms of JM Pt/VC and Pt/CIC85 (i.e., 85 nm pore size), prepared by both the ethanol and butanol synthesis methods, in 0.5 M H2SO4. Even though the theoretical specific surface areas were 70-80 m2/gPt (particle size of 3-3.5 nm), the electrochemical active surface area (ECSA) was found to depend on the synthesis method and the carbon support. The ethanol oxidation activity of catalysts per Pt area for the three carbon supports is shown in Figure 2. A strong dependence on the carbon microstructure was observed, with Pt/CIC and Pt/KB, showing a higher activity than Pt/VC, likely due to their higher content of mesopores in the catalyst layer [2]. The correlation between catalyst activity and the carbon microstructure for each synthesis method will be discussed in detail. References: 1. J. Xie, Q. Zhang, L. Gu, S. Xu, P. Wang, J. Liu, Y. Ding, Y.F. Yao, C. Nan, M. Zhao, Y. You, Z. Zou, Nano Energy (2016) 21, 247–257. 2. T. Soboleva, X. Zhao, K. Malek, Z. Xie, T. Navessin, S. Holdcroft, ACS applied materials and interfaces (2010) 2, 2, 375–384. Figure 1

Ethanol is a promising fuel for transportation applications, given its low toxicity and easy access from feedstock fermentation. However, the combustion of ethanol to regain the stored energy is highly inefficient and thus a non-combustion process, such as the electrochemical oxidation of ethanol in a fuel cell, is desirable for utilizing the stored energy. To achieve high conversion efficiencies, an appropriate catalyst for ethanol oxidation must be developed. While Pt is a good material for this purpose, it is prone to poisoning by strongly adsorbed intermediates, e.g., CO. To address these shortcomings, Pt can be nanostructured and combined with other metals, resulting in superior activity and longer lifetimes. In the present work, Ir core@Pt shell nanoparticles (NPs) were synthesized, with varying Pt shell coverages (less than one monolayer), ensuring that some Ir is exposed and thus allowing the bifunctional effect [1], electronic [2], and strain effects [3] to all play a role in the catalysis of the ethanol oxidation reaction. The core@shell NPs were synthesized using the polyol method [4], producing a core that was ca. 3 nm in diameter and then loaded (10 mass %) onto Vulcan Carbon powder. These catalysts were then characterized by wavelength-dispersive X-ray spectroscopy (WDS) and thermogravimetric analysis to determine the relative percentage of each metal present in each nanoparticle and to confirm the metal loading onto the carbon, respectively, while TEM analysis confirmed the expected NP size and distribution. The electrocatalytic activity of these materials was evaluated using a three electrode system, all in 0.5 M H2SO4 + 0.01 - 1 M ethanol at room temperature. Overall, it is shown that these Ir core@Pt shell NPs are notably more active than Pt NPs of the same size and also produced using the polyol method. The activity of the catalysts increases with ethanol concentration, but less than linearly, and sweep rate studies revealed the presence of electroactive surface-bound reaction intermediates. The stability of the catalysts has also been investigated using cyclic voltammetry and chronoamperometry experiments. By studying the effect of Pt shell coverage on the Ir core NPs, the mechanism by which Ir enhances the activity of Pt during ethanol oxidation is now being determined. References: El Sawy, E. N.; Molero, H. M.; Birss, V. I. Electrochimica Acta (EAST13-0480) 2013. Chen, Y. M.; Yang, F.; Dai, Y.; Wang, W. Q.; Chen, S. L. Journal of Physical Chemistry C 2008, 112, 1645-1649. Zhang, X. T.; Wang, H.; Key, J. L.; Linkov, V.; Ji, S.; Wang, X. L.; Lei, Z. Q.; Wang, R. F. Journal of The Electrochemical Society 2012, 159, B270-B276. Alayoglu, S.; Eichhorn, B. Journal of the American Chemical Society 2008, 130, 17479- 17486.

In this article, studies on coordinative properties of 5,11,17,23-tetra-p-tert-butyl-25,27-bis(N-p-nitrophenylureido-butoxy)-26,28-dipropoxycalix[4]arene (Cx2) are presented. Since this anion-receptor was previously used as an additive to solid polymer electrolytes, the correlation of the data presented here and the role of anion-receptors in this type of electrolytes is discussed. The formation constants of salt–receptor complexes and receptor self-complexation (dimer formation) are estimated in the solution in the non-interacting solvent using 1H and 19F NMR titration. Independently, the affinity of the Cx2 to low molecular weight analogs of PEO and some other organic solvents in this system was tested using the same technique. The estimated values of the formation constants are used in the discussion the role of the anion-receptor in the changes of concentration of ions, ionic agglomerates and complexes of Cx2 in the system comprising salt, solid or liquid matrix and anion-receptor.

1-Ethyl-3-methyl imidazolium hydrogensulfate (EMIHSO4), a non-fluorinated IL, was studied both as liquid and polymer electrolytes for electrochemical capacitors [1]. While EMIHSO4exhibited a reasonable ionic conductivity, improvement in proton conductivity is possible by altering the structure of the cation, which warrants further investigation. The objectives of this study are twofold: to investigate the effect of cationic functional groups on the properties of the IL; and to select and characterize the IL system with optimum proton conductivity. The electrolytes were prepared using ILs with different cations, namely 1-ethyl-3-methyl imidazolium hydrogensulfate (EMIHSO4), 1-methylimidazolium hydrogensulfate (MIHSO4), and imidazolium hydrogensulfate (ImHSO4) in methanol solutions. For comparison, a solution of EMIHSO4 with propylene carbonate (PC), an aprotic solvent, was prepared with the same concentration as those in methanol-based electrolytes. To demonstrate the proton conductivity of the electrolytes, standard two-electrode cells were assembled utilizing pseudocapacitive electrodes such as RuO2and nanocarbon/polyoxometalate (POMs) composites [2].The cell performance were characterized using cyclic voltammtery (CV) and ac impedance spectroscopy. RuO2 exhibits pseudocapacitance via a coupled proton–electron transfer in a protic electrolyte. Figure 1 shows the CV profiles of the RuO2-based cells in all electrolytes. The ImHSO4 and MIHSO4-based cells demonstrated similar CVs and the highest capacitance performance. Their higher capacitance compared to EMIHSO4-based cell indicates the higher proton conductivity of ImHSO4 and MIHSO4, which can contribute to the electrochemical reactions of RuO2 electrodes. Due to the role of solvent on proton dissociation, the cell performance was superior using EMIHSO4/MeOH electrolytes than that for EMIHSO4/PC. The proton conductivity of PILs was further examined on a carbon/POM electrode and compared to the bare carbon electrodes. POMs involve fast and reversible multielectron transfer reactions in proton containing electrolytes. For a better comparison, the respective carbon/POM cells were also tested in 0.5M H2SO4. The electrochemical performance of the carbon/POM-based cells in the PIL electrolytes followed a similar trend as those for RuO2-based electrolytes. Figure 2 (a) shows the CV profiles of the carbon/POM-based cells and the bare carbon in ImHSO4/MeOH electrolyte. The increased capacitance of the carbon/POM cell over that for the bare carbon implies the proton conducting characteristic of ImHSO4 electrolyte which participates in the redox reaction of the POM. Figure 2 (b) presents the capacitance ratio of the carbon/POM cells in the respective PILs to H2SO4 electrolyte. ImHSO4-based cells showed the highest capacitance ratio followed by MIHSO4 and EMIHSO4in both MeOH and PC solutions. Imidazoles consist of two nitrogen sites, and their protonated and unprotonated nitrogen functions may act as proton donor and acceptor in proton transfer reactions. As the nitrogen sites decrease in MI and EMI cations, the contribution from proton conduction becomes smaller. More details on optimizing the proton conductivity of these PILs for room temperature applications, especially polymer electrolytes will be presented. References: [1] S. Ketabi, Z. Le, and K. Lian, Electrochemical and Solid-State Letters, 15 (2), A19, 2012. [2] G. Bajwa, M. Genovese, and K. Lian, ECS Journal of Solid State Science and Technology, 2 (10), M3046, 2013. Figure 1. CVs of RuO2 cells in ImHSO4, MIHSO4, EMIHSO4 methanol-based, and EMIHSO4/PC electrolytes at a scan rate of 100 mV/s Figure 2. (a) CVs of carbon/POM and bare carbon cells in ImHSO4/MeOH; (b) capacitance ratio of carbon/POM cells in respective PILs to H2SO4 electrolyte (all tests at a scan rate of 100 mV/s)

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