bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvement in Electrochemical Properties of Ionic Liquid PYR14tfsi By Mixing with BMImBF4 As High Safety Electrolyte
Authors: Lee Ching-Feng , Chang Chien-Min , Wang Pin-Han , Chen Hwang-Sheng , Chen-Yang Yui Whei 
Published: February 2020

As is known, the characteristics of electrolyte play a significant role in lithium-ion batteries in terms of high conductivity, good compatibility with electrode material and safety. Because of the volatility and flammability of the traditional organic electrolytes, the safety risk has been a big concern for the batteries, especially when it is used in hybrid electric vehicles (HEVs) and electric vehicles (EVs). On the other hand, the room temperature ionic liquids (RTILs) usually are low volatile, non-flammable liquids with wide electrochemical window that benefit to use as electrolytes in high-safety lithium battery. Since the chemical and physical properties are strongly related to combination of the cations and anions composed, unique ionic liquids may be designed for the particular application. Recently, the RTILs formed by imidazolium, pyrrolidinium, piperidinium cations and hexafluorophosphate (PF6
-), tetrafluoroborate (BF4
-), bis(trifluoromethanesulfonyl)imide (TFSI-) anions have been frequently used as the electrolytes for lithium-ion batteries. However, as reported, the organic solvents i.e. ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC) and diethyl carbonate (DEC), which are used for the traditional liquid electrolytes, have often been mixed with the RTIL for reducing the viscosity to increase the conductivity. Yet, the thermal stability can’t be improved essentially. In this study, a solvent-free ternary RTIL-based electrolyte system has been constructed by the RTILs, 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4), 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Three different electrolytes with various compositions are prepared and characterized by FTIR, thermogravimetric analysis, differential scanning calorimetry, linear sweep voltammetry, conductivity meter and rheometer. The results show that all three electrolytes are thermally stable up to about 350℃ and have wide electrochemical windows (~5V). Besides, the lowest viscosity and the highest conductivity obtained were 66.2 cP and 2.76 mS, respectively. The highest discharge capacity of the LiFePO4/electrolytes/Li half-cell obtained in the voltage range of 2.5–4.3 V at 0.2C and 55℃ is 158 mAh g-1. This study reveals that the RTIL-based ternary electrolyte is a promising electrolyte candidate for the high-safety lithium-ion battery.
Acknowledgements
The authors gratefully acknowledge the Ministry of Science and Technology, Taiwan, R. O. C. and Chung Yuan Christian University for supporting this research work.
Highly Fractal MoS2 Electrodes Modified By Ammonium Thiomolybdate As Efficient Hydrogen Evolving Electro-Catalysts
Authors: Ramirez-Caro Alejandra , Redeker Frenio A. , Bierwirth Stefanie , Bogdanoff Peter , Ellmer Klaus , Fiechter Sebastian 
Published: February 2020

Due to the high energy density of hydrogen it could play an important role as energy storage medium replacing fossil fuels in the future. To produce it in large quantities “artificial leaf”-type structures could be used converting solar light into this fuel by electrochemical decomposition of water. Since this process is most efficient working under acidic conditions in an electrolyzing system semiconducting materials are required on the one hand efficiently absorbing sunlight and generating electron-hole pairs, the energy of which is high enough to split water. To reduce overvoltages on the other hand electro-catalysts are in demand lowering in addition the overvoltages at cathode and anode side.
To replace costly platinum as most efficient HER catalyst for more than a decade attempts were made to replace this noble metal by molybdenum sulfides. It has been shown that nanoparticles of MoS2 are most efficient consisting of three to four S-Mo-S slabs deposited on a suited support, e.g. MoO3-x, multiwalled carbon nanotubes (MWCNT) and activated carbon paper [1, 2].
In this contribution, we report on the deposition of (NH4)2Mo3S13 particles on highly fractal MoS2 layers deposited by reactive magnetron sputtering. Best results were obtained after drop casting a solution of ammonium thiomolybdate on a sputtered MoS2 film as shown in Figure 1. The modified electrode exhibited an overvoltage of -220mV at a current density of 10mAcm-2. Since it is known that the edges of the hexagonal MoS2 crystallites of the sputtered film are containing the highly catalytically active sites this contribution will address the nano-architecture of the modified electrodes.

Figure 1
(Invited) In-Situ X-Ray Structural Characterization of Water-Splitting Catalysts in Artificial Photosynthesis
Authors: Tiede David M , Kwon Gihan , Kim In Soo , Emery Jonathan D , Martinson Alex B. F. 
Published: February 2020

Resolution of structures and structural dynamics for catalysts at active electrode interfaces is necessary to resolve mechanisms for function and assembly in solar fuels applications. We have been developing porous, high-surface area, low X-ray background, 3-D electrodes for interfacial structural analysis of molecular and amorphous metal oxide water-splitting catalysts using X-ray scattering and atomic pair distribution function (PDF) analysis. We demonstrate the opportunity to use ALD-ITO coated microchannel plates and other micro- to nano-porous substrates for characterization of domain structures for amorphous metal oxides water-oxidation catalysts used in artificial leaf assemblies. This presentation will compare domain structures resolved for amorphous cobalt oxide films formed electrolytically as a function of ligand and electrolyte anion variation. For cobalt oxide catalysts, the results show that phosphate is unique in restricting domain size to small, single-layer domains where defects and edge distortions can be resolved. The results show that catalytic currents for do not scale with the domain edge content in the cobaltate films, which are the presumed sites for water oxidation catalysis, but instead track the extend of domain layering and conductivity properties of the films. These results support the view that overall catalytic activity in amorphous cobaltate thin films is determined by the charge accumulation and transport properties. We have extended these techniques demonstrate the opportunity to measure PDF for homogeneous water oxidation catalysts. PDF measurements with 0.2 Å spatial resolution are found to be sufficient to resolve redox and catalytic state dependent changes in ligand structure. This work establishes a foundation for extending the X-ray PDF method for the analysis of atomic structure changes in molecular catalysts driven by excited-state, sequential single electron photo-chemistry.
(Invited) On the Selectivity and Durability of Electrocatalysts for the Conversion of CO2 to Value Added Fuels
Authors: Zhou Xiao-Dong , Wu Jingjie 
Published: February 2020

Rising emissions of CO2 in the atmosphere have become an increasing concern in recent years as growing evidence links greenhouse gasses to global warming, yet these emissions are the by-product of the majority of essential energy sources in place today (e.g. fossil fuels). In addition to efforts to capture and store CO2 in hopes of relieving the greenhouse effect, the conversion of CO2 to value added fuels and chemical feedstock is an attractive proposition that may provide an alternative solution to both the current energy crisis and climate issues. In this presentation, an overview will be provided on the utilization of a full electrochemical cell to study the selectivity of durability of metallic and nonmetallic electrocatalysts for the conversion of CO2 to gaseous or liquid fuels. Special attention will be given to the chemical origin of selectivity and durability of this electrochemical process.
(Invited) 2D Nanosheet-Based Hybrid Photocatalysts for Solar Fuel Production
Authors: Hwang Seong-Ju 
Published: February 2020

Solar energy is one of the promising renewable energy sources that can fulfill the rising global demand for sustainable energy. One of the most effective approaches to harvest solar energy is the photoinduced production of solar fuel likes H2 and C1 compounds. Despite a great deal of researches, most of inorganic photocatalysts ever-developed is not appropriate for the visible light-induced water splitting because of unsuitable band structure and poor stability. To circumvent this problem, we have tried to synthesize hybrid-type visible light active photocatalysts via self-assembly between two kinds of nanostructured semiconductors including 2D nanosheets and 0D nanoclusters. As building blocks, the 2D nanosheets of layered metal oxide, layered double hydroxide (LDH), and reduced graphene oxide (rG-O) are synthesized by the exfoliation process of the pristine layered materials. The obtained 2D inorganic/rG-O nanosheets are reassembled with each other or hybridized with other 0D nanoparticles. The band structure and surface area of wide bandgap layered metal oxide can be effectively tailored through the hybridization with LDH 2D nanosheets or transition metal oxide/metal chalcogenide 0D nanoparticles. The obtained nanohybrids show promising photocatalytic activity to produce solar fuel under the irradiation of visible light.
Alternative Catalyst for CO2 Electrochemical Reduction
Authors: Varela Ana Sofia , Ju Wen , Roldan Beatriz , Strasser Peter , Mistry Hemma , Möller Timmey 
Published: February 2020

Direct electrocatalytic conversion of CO2 to hydrocarbons is a promising alternative for the production of carbon based chemicals. Ideally, the driving force for this process would be electricity from renewable sources, making this process CO2 neutral.1 Copper is the most studied material as catalyst for CO2 reduction reaction (CO2RR) given its unique ability to produce hydrocarbons in considerable amounts. Nevertheless, the reaction’s poor energy efficiency and selectivity remain a major challenge.2 Therefore the technological viability of this process is contingent on the development of novel and efficient catalyst.
In recent years different groups have demonstrated that oxide derived copper foil catalysts exhibit lower onset potentials for CO2RR and high selectivities towards C2 products.3,4 Future applications, however, will require the use of supported nanoparticles. Herein we will present the use of Cu2O nanoparticles as catalyst for this process. We demonstrate that these nanoparticles have a lower onset potential for CO2RR in comparison with metallic Cu, which makes them a promising catalyst for this process.
Moreover we will discuss the use of alternative catalyst such as heteroatom-doped carbon.5 We show that these materials meet and exceed the activity and selectivity of traditional Au catalysts for the production of syngas, offering a cost-effective alternative. Furthermore, we provide evidence that sufficiently strong interaction between CO and the metal enables the protonation of CO to form hydrocarbons. In order to get more insight into the role of the metal atom, changes in the chemical stat under operando conditions observed via X-ray absorption fine-structure spectroscopy (XAFS) will be also discussed.

Figure 1: Scheme of the as heteroatom-doped carbon catalyst for CO2RR. b) Faradaic selectivities of CO and H2 after 10 min reaction at constant electrode potential in CO2 saturated 0.1M KHCO3 at 0.785 mg/cm2 catalyst loading. Lines to guide the eye.

References

(1) Gattrell, M.; Gupta, N.; Co, A. Ener. Convers. Manag.
007, 48, 1255.
(2) Kortlever, R.; Shen, J.; Schouten, K. J. P.; Calle-Vallejo, F.; Koper, M. T. M. J.Phys. Chem. Lett.
2015, 4073.
(3) Li, C. W.; Kanan, M. W. J. Am. Chem. Soc.
2012, 134, 7231.
(4) Kim, D.; Lee, S.; Ocon, J. D.; Jeong, B.; Lee, J. K.; Lee, J. Phys. Chem. Chem. Phys.
2015, 17, 824.
(5) Varela, A. S.; Ranjbar Sahraie, N.; Steinberg, J.; Ju, W.; Oh, H.-S.; Strasser, P. Angew. Chem. Int. Ed.
2015, 54, 10758.

Figure 1
(Invited) CO2 Photoreduction Under Visible Light By Oxygen-Deficient TiO2 with Co-Exposed {001} and {101} Facets
Authors: Li Ying , Liu Lianjun , Yang Kesong 
Published: February 2020

This work for the first time reports engineered oxygen-deficient, blue TiO2 nanocrystals with co-exposed {101}-{001} facets (TiO2-x{001}-{101}) to enhance CO2 photoreduction under visible light. The TiO2-x{001}-{101} material demonstrated a relatively high quantum yield (0.31% under UV-vis and 0.134% under visible light) for CO2 reduction to CO by water vapor and more than four times higher visible light activity compared with TiO2 with a single {001} plane or {101} plane and TiO2(P25). Possible reasons are the exposure of more active sites (e.g., under-coordinated Ti atoms and oxygen vacancies), the facilitated electron transfer between {001} and {101} planes, and the formation of a new energy state (Ti3+) within TiO2 band gap to extend visible light response. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study was applied to understand the roles of co-exposed {001}-{101} facets and Ti3+ sites in activating surface intermediates. The in situ DRIFTS analysis suggested that the co-exposed {001}-{101} facets increased the capacity of reversible CO2 adsorption and that the combination of {001}-{101} and Ti3+ enhanced the activation and conversion kinetics of adsorbed species. The visible light responsive TiO2-x{001}-{101} material is not oxidized after long time exposure to an air environment.
(Invited) Chalcopyrites and III-V Semiconductors for Solar Water Splitting--a Detailed Look at the Electronic and Chemical Surface Structure
Authors: Heske Clemens , Blum Monika 
Published: February 2020

This presentation will discuss the chemical and electronic surface properties of Cu(In,Ga)(S,Se)2- and GaInP2-based materials in view of their use in solar water-splitting devices. Many of the primary requirements for photoelectrochemistry (such as efficiency and stability) are directly related to such properties, but it is generally quite difficult to paint a comprehensive surface picture, in particular in operando environments.
The talk will focus on results obtained with a tool chest of soft x-ray and electron spectroscopies, with primary emphasis on high-brilliance synchrotron radiation experiments. It will be shown how photoelectron spectroscopy (PES), also under “ambient pressure” conditions, inverse photoemission (IPES), x-ray emission spectroscopy (XES), and x-ray absorption spectroscopy (XAS) can be suitably combined to derive surface electronic band gaps, study local chemical bonding and electronic level alignment, and gain insights into chemical stability.
Electrochemical Deposition of Cu2O Thin Film As Efficient Photocatalyst for Water Splitting Reaction
Authors: Hasan Maksudul , Mavrokefalos Christos K. , Compton Richard G , Rohan James F. , Foord John S. 
Published: February 2020

Solar water splitting can form the basis of a sustainable hydrogen based energy economy, however the system requires optimisation in terms of cost and performance on a scale commensurate with the global energy demand. Photocatalysts consist of solar spectrum absorber semiconductor materials and co-catalysts as the redox mediator for hydrogen and oxygen evolution reactions. The key factors for efficient solar water splitting process to occur with such photocatalysts are a semiconductor with a sufficiently narrow band gap to absorb visible lights, a suitable thermodynamic potential for the redox reactions, and stability against photocorrosion. However, current photocatalysts also suffer from undesirable photoelectron-hole (charge carrier) recombination within the semiconductor due to their short diffusion path lengths and lifetimes, which results in fewer than 10% of the incident photons being used for water splitting.
Cuprous Oxide (Cu2O), one of the few naturally occurring p-type metal oxides, is the most promising candidate for an efficient photocathode because of its earth abundance, a band gap of 2.0 eV, which enables efficient visible light absorption, a scalable CMOS compatible deposition technique (e.g., electrodeposition), and favourable energy band position i.e. conduction band lies 0.7 eV negative of the hydrogen evolution potential that drives off half of the water reduction reaction without of any external bias. However, the application of Cu2O as photocathode is limited by two drawbacks; fast photoelectron–hole recombination owing to short carrier diffusion length and self-photo corrosion in aqueous solution under illumination since the potentials of Cu2O reduction and oxidation to metallic Cu and CuO, respectively, lie within the bandgap. Hence, the solar-to-fuel conversion efficiency on Cu2O depends on how fast the photoelectron can be extracted to the reduction reaction sites and inhibition of electrolyte access to Cu2O surface. A thin protective coating and a heterostructure in the seed layer of the electrochemically deposited Cu2O film enhance the overall photocatalytic performance versus the Cu2O film alone. The thickness of the Cu2O film was optimised to avoid the charge carrier recombination towards the efficient and stable photocatalytic performance. The photocatalytic performance of Cu2O thin film is shown in Fig 1, in which the film performance is unexpectedly high and only dropped to 22% after the first cycle at 0.0 VRHE, after which it stabilises. This presentation will discuss our current research to develop cheap and efficient photocatalysts and their enhancement mechanism towards photocatalytic water splitting reactions.

Figure 1
(Invited) Modeling and Its Use in Interpretation of Experimental Results for Electroactive Films at Electrodes
Authors: Sunde Svein , Tjelta Morten 
Published: February 2020

Electrochemical characterization of electroactive films at electrodes requires models for interpretation of experimental results. Such films at electrodes may range in complexity from dense films for which uniform one-dimensional diffusion of intercalants provides an adequate description to porous systems with conductivity varying with state of charge and where more than one species may contribute to film conductivity. We describe here on-going attempts at extending models to these more complex situations within an analytical framework, and focus on interpretation of experimental results in view of the models. We thus review previous models suggested for describing the impedance of porous electroactive films of mixed conductivity, and extensions of the theory to include the effect of space charges within the porous matrix on the electrode capacitance. The Poisson-Boltzmann equation was thus solved for spherical geometry by use of Green’s functions, resulting in an analytical (closed form) integral expression that could be solved iteratively using a solution to the linearized Poisson-Boltzmann equation as the first order approximation for the potential. Practically identical results were produced when solving the governing equation by finite differences. Calculated concentration and potential profiles can be used to determine at which combination of carrier concentration and radius a particle is too small to sustain an extended space charge layer. Also, the surface capacitance-potential behavior has been obtained for extrinsically and intrinsically semiconducting particles. For the intrinsic case the behavior had a minimum value at the flatband potential. Extrinsic particles approached Mott-Schottky behavior at high dopant levels or large radii. These results will be discussed in the context of intercalation in porous electrodes, as well as extensions to other measurement methods than impedance.
References
[1] S. Sunde. I. A. Lervik, L.-E. Owe, and M. Tsypkin, “An impedance model for a Porous Intercalation Electrode with Mixed Conductivity”, J. Electrochem. Soc., 156 (2009) B927
[2] Sunde, S. , Lervik, I.A., Tsypkin, M., Owe, L.-E. , “Impedance analysis of nanostructured iridium oxide electrocatalysts”, Electrochimica Acta, 55 (2010) 7751 – 7760
[3] M. Tjelta and S. Sunde, “Current-distribution effects on the impedance of porous electrodes and electrodes covered with films”, J. Electroanal. Chem. 737 (2015) 65 -- 77
(Invited) Development of an Inductively Heated Ultramicroelectrode for SECM
Authors: Wipf David O , Dowell Timothy J 
Published: February 2020

An underused parameter in electrochemistry is temperature. Controlling or altering the temperature at the electrode can provide several experimental benefits. Changes in kinetics and equilibrium constants are readily observed. Temperature dependent potential shifts and wave shapes can allow unique identification of chemical species. Thermal effects can also renew catalytic surfaces and improve mass transport by increasing diffusion coefficients or inducing convective currents.
Temperature control is readily achieved using thermostated electrochemical cells, but this produces several practical problems that may require addressing. These include destruction of thermally unstable compounds, loss of volatile components, and reference electrode potential shifts. In addition, the large thermal mass of an electrochemical cell does not favor rapid temperature changes. These drawback can be minimized or eliminated by directly heating the electrode in a non-isothermal mode. (1) For example, using high-voltage AC to heat cylindrical electrodes of mini to macroscopic dimension. These, and other types of electrode heating, produce a heated zone in the solution immediately adjacent to the electrode surface. This then permits considering using temperature as a parameter in electrochemical imaging (cf. SECM) because of the potentially rapid temperature rise and fall at microscopic electrodes. However, now several disadvantages are produced in the non-isothermal mode. These include reduced control over the temperature achieved, increased complexity of the experiment, and lower temperature precision.
Our goal is to develop heated-tip microelectrodes compatible with SECM and other SPM imaging. We have developed a novel inductive heating procedure that can be used with electrodes of 1-20 μm. A small induction coil is placed entirely inside the electrode housing allowing the electrode shank to be heated by galvanically isolated induction. This electrode is physically small and is readily incorporated into the SECM instrument with no instrument modifications.
In this presentation, we demonstrate the rapid heating and cooling produced by the inductive method and show, using effects on kinetics and equilibrium potentials, that the temperature at the tip of the ultramicroelectrode may be altered up to the boiling point of the solvent. We also use finite element modelling to model the heating process and to estimate the temperature at the tip based on the geometry of the induction coil, the electrode material, the electrode body and any active cooling, and the solvent. In addition, we are modeling the rate of temperature rise and return to ambient relative to a heating pulse. Finally, we model the possibility of indirect, transient heating the imaged substrate by the heat flow from the closely-spaced heated tip.
(1) Gründler, P.; Flechsig, G.-U. Microchim Acta 2006, 154 (3-4), 175–189.