bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Innovations in Ionic Liquids Electrodeposition of Metals
Authors: Reddy Ramana 
Published: February 2020

A novel pathway for the high energy efficiency electrodeposition of metals from metal oxides and metal compounds by means of electrolysis in ionic liquids at low temperatures was investigated. Experimental results for electrochemical deposition of Zn from ZnO and Cu from Cu2O, Pb from PbO using Urea ((NH2)2CO) and Choline chloride (HOC2H4N(CH3)3
+Cl-) or (ChCl) are discussed. The results showed that pure metal was deposited on the cathode. Successful deposition of metal from metal oxide dissolved in Urea/ChCl (2:1) was accomplished with efficiency greater than 87%. Electrodeposition of aluminium and titanium using imidazolium chloride ionic liquids with the addition of AlCl3 and TlCl4 were carried out at low temperatures. The cathode deposits obtained were dendrite free pure aluminium (>99.9% pure) and Al-Ti (up to 37 wt %) alloy. Cathode current densities of up to 500 A/m2for electrowinning of aluminium were achieved.
The surface modification of electrodes not only improved the cathode current density but also eliminated the dendritic deposition of metals. Use of glassy surface finish, aluminum cathode and aluminum alloy anode improved the current density of the process. The critical cathode overpotential and limiting current density at which aluminum dendritic growth begins was determined as -0.53 V and 518 A/m2, respectively. Lower overpotentials (<0.42 V) prevent the dendrite formation in the aluminum deposits. It was concluded that the overpotential is the key in preventing dendrite formation.
A 3-D mathematical model (CFD) was developed for the batch reactor electrodeposition of metals process. The optimum conditions for electrodeposition of metals and alloys were determined. The model results are in good agreement with the experimental data for the Al electrowinning process.
The advantages of the electrodeposition of metals using ionic liquids compared to industrial aqueous metals processes are low temperature, low energy consumption, and low pollutant emissions.
(Invited) Towards Advanced Functional Natural Polymer Materials through Ionic Liquid Based Methods
Authors: Trulove Paul C , Durkin David P. , Fox Eric T , Haverhals Luke M. , Fahey Patrick J , Ryall Katherine E. , Head Audrey C. , Ye Tao , Shuai Danmeng , Fairbrother D. Howard , De Long Hugh C. 
Published: February 2020

Throughout history humankind has exploited the remarkable properties of natural polymers such as silk and cellulose. In modern times, these natural materials still possess properties that rival the most advanced synthetic polymers. Recent work has shown ionic liquids (IL) to be effective solvents for the dissolution of a wide variety of natural polymers, and new materials can be created from these natural feedstocks by processes that involve their full dissolution and subsequent reconstitution. However, many reports show that the dissolution and reconstitution processes eliminate the native polymer structure, often with negative consequences to the physical properties of the resulting materials. Alternatively, if only the surface layers of these natural materials are mobilized through an ionic liquid facilitated process called Natural Fiber Welding (NFW), the underlying material retains its native character and mechanical properties while still allowing for significant material modification. Furthermore, the addition of functional materials (e.g. magnetic, conductive, antimicrobial) into the IL welding solution, allows for these substances to be entrained in and on the surface of the substrate imparting unique properties to the natural materials.
Our group has endeavored to utilize NFW to modify natural materials to introduce novel functionalities. This work has encompassed the incorporation of a wide variety of polymeric, organic and inorganic materials into natural fiber matrices. Through the introduction of the appropriate materials we have been able to impart capacitive, conductive, catalytic, magnetic, optical, antimicrobial, and/or fire retardant functionalites into natural polymeric materials. In this presentation we will show our most recent efforts utilizing NFW to prepare novel functional natural materials.
Towards Better Understanding of Molecular Solvent Behavior in Ionic Liquid-Biopolymer Mixtures
Authors: Fox Eric T , Fahey Patrick J , Gobet Mallory , Munoz Stephen , Head Audrey C. , Greenbaum Steven , De Long Hugh C , Trulove Paul C 
Published: February 2020

Some ionic liquids (ILs) are notable for their ability to solubilize traditionally difficult to dissolve natural materials such as cellulose, silk, and wool keratin. NMR studies have shown that this ability is due predominantly to the interaction of chaotropic anions present in the IL, such as Cl- or acetate, with the hydroxyl groups present on polymeric materials. When molecular solvents are added to such mixtures, differing behaviors occur depending on the nature of the added solvent. Polar protic solvents generally serve as antisolvents, inducing the precipitation of dissolved materials. In contrast, polar aprotic solvents behave as cosolvents and are able to be added in significant fractions without causing the reconstitution of dissolved materials. It is generally understood that this differing behavior is the result of whether or not the molecular solvent preferentially interacts with the IL anion, thus preventing the anion from interacting with the polymer hydroxyl groups. However, little experimental work has been published to verify this hypothesis.
In this study, the physical and transport properties (density, viscosity, ionic conductivity, and ion diffusion coefficients) are reported for 1-ethyl-3-methylimidazolium acetate (EMIAc) containing dissolved cellulose. The properties of these EMIAc-cellulose solutions were studied with no added molecular solvent, with added acetonitrile, or with added water. The fraction of ions present in the IL that are “free” (the Ionicity values) were calculated for each solution. The addition of molecular solvents to an EMIAc-cellulose solution results in significant changes in the mobility of all species present, and offers a means to better understand the molecular interactions that govern biopolymer solvation in ILs.
SOFC Anode Process Characterization By Means of a Novel Spot-Sampling Set-up for in-Operando Gas Analysis
Authors: McPhail Stephen J. , Pumiglia Davide , Santoni Francesca , Conti Bruno , Boigues Muñoz Carlos , Bosio Barbara , Carlini Maurizio 
Published: February 2020

The development and operation of an innovative experimental setup is presented for in-depth, in-operando characterization of anode processes of Solid Oxide Fuel Cells.
The idea behind this project is to realize a setup enabling the measurement of temperature and gas compositions using eleven points of sampling distributed over the anode surface. Simultaneous temperature measurement and gas chromatography are employed to detect the variation of thermodynamic and chemical conditions across the anode surface in steady state and in real time. The particular location of each sampling point is chosen in such a way as to minimize interference in the flow pattern across the anode but maximizing the spatial information of the measurements taken. Thus, it is possible to investigate the evolution of chemical reactions occurring during the operation of the cell, identified with a spatial resolution covering the whole surface of the anode in order to distinguish edge effects from bulk processes. Sampling settings are tailored to analyse representative specimens of anode gas without altering local conditions. Moreover, the novel housing allows for full simultaneous (bulk) electrochemical characterization through polarization curves and electrochemical impedance spectroscopy (EIS), maximizing the data output from a given experiment without significantly affecting the cell response during the characterization.
This experimental setup is particularly important for the direct fuelling of SOFCs with natural gas, biogas or syngas, where the dynamic processes of internal reforming can create severe local gradients of temperature and gas compositions, inducing stresses and possible carbon deposition. Single cell tests have been carried out on intermediate-temperature, commercial SOFCs fed with simple hydrogen and selected syngas compositions to assess the thermochemical response of the SOFC at different current densities and create a detailed spatial mapping of critical hotspots correlated with operating conditions and inlet gas compositions. It is thus possible to identify areas within the operational space that are conducive to better uniformity of conditions, presumed to enhance SOFC durability, allowing to provide recommendations for fuel pre-conditioning processes as well as SOFC operation modes. Ultimately, it is envisaged to establish simplified but effective control algorithms based upon the correlation of the detailed, real-time spatial mapping with key parameters that are easily monitored in a real SOFC system.
Experimental data will be useful to investigate phenomena occurring on the cell plane also with the help of a model based on finite element method that can simulate locally the behavior of the cell in order to validate the experimental map of temperature and composition of gases on the cell.
Multilayer Active Nanostructures of Metal Oxide Semiconductors-Assisted Photooxidation of Wastewater for Voltammetric Determination of Heavy Metals
Authors: Miecznikowski Krzysztof , Biadun Ewa , Gajewska Sylwia , Krasnodebska-Ostrega Beata 
Published: February 2020

The presence of organic matter (e.g. surfactants) is the most crucial problem in many analytical methods, such as inductively coupled plasma mass spectrometry (ICP MS), graphite furnace atomic absorption spectrometry (GF AAS) or electrochemical methods (stripping voltammetry). Voltammetry is a sensitive method of metal determination, only one an alternative to ICP MS. Only one limitation of the method is an influence of the organic matrix on the measurements. After the wet digestion with H2O2 accelerated with UV irradiation the evaporation of an excess of reagent is required. We present the application of “sunlight” assisted digestion in the presence of bare WO3 or multilayer metal oxide semiconductors (e.g. WO3 and Fe2O3) to the decomposition of dissolved organic matter, using the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant (1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton™X-114) in natural water samples, prior to the determination of traces residues of lead by stripping voltammetry methods. The results of the study showed firstly that the preparation of reproducible WO3 layers characterized by high mechanical and chemical resistance was possible, and secondly that it was also possible to obtain a high efficiency of decomposition, equal in efficiency to that of the reference method, which was the hydrogen peroxide oxidation assisted by UV, with evaporation nearly to dryness. The developed procedure is suggested to be a no-reagents method for the decomposition of added SDS, leading to 100 % recovery of added Pb (II). Physicochemical properties (structure, morphology and spectroscopic identity) of the resulting hybrid (composite) WO3 films were assessed using X-ray diffraction, scanning electron microscopy, as well as UV-Vis and Raman spectroscopies. The electrochemical method (anodic stripping voltammetric - ASV) will be applied in practical study of the determination of various trace metals in natural water samples. For comparison, GFAAS and ICP-MS measurements would be performed as reference methods confirming the correctness of electrochemical measurements due to their different tolerance to the presence of the organic matrix in the samples.
Photoelectrochemical Properties of Si-Doped InGaN Photoelectrode Grown By Plasma Assisted Molecular Beam Epitaxy
Authors: Shen Yu-Min , Chen Li-Chyong , Chen Kuei-Hsien 
Published: February 2020

In this work, high quality epitaxial Si-doped InGaN films were grown on Si (111) substrate using plasma assisted molecular beam epitaxy (PAMBE) via controlling of Si flux. X-ray diffraction results showed controllable formation of c-axis Si:InGaN with different Si compositions, while XPS results indicate the Si was subsisted Ga site. Transmission electron microscope image showed the Si:InGaN films were grown epitaxially without phase separation with lattice mismatch between Si:InGaN and Si substrate of less than 1%. Photoelectrochemical (PEC) study was done under NaOH solution to achieve an optimum efficiency of 1.6% at 0V (vs. Ag/AgCl) with sample of Si flux at 6 x 10-9 torr. The series resistances of InGaN and Si:InGaN were reduced from 43.6Ω to 18.7Ω which was determined utilizing electrochemical impedance spectroscopy (EIS). The carrier concentration between Si:InGaN and InGaN were 9.4 x 1016 and 2.6 x 1018 cm-3, which was lead 2 times higher photocurrent density (0.8 and 1.6 mA/cm2, respectively) from Mott Schottky plot. Factors that might influence the PEC performance, such as the flat band position, crystallinity, and protons diffusion length will be addressed in this paper to obtain better insight into the issue of Si:InGaN for PEC.
Keywords: plasma assisted molecular beam epitaxy, Si:InGaN, water splitting, carrier concentration

Figure 1
Can Platinum Scale for PEC Hydrogen Evolution at the Terawatt Level?
Authors: Vesborg Peter C. K. , Bodin Anders , Pedersen Thomas , Sebok Bela , Mei Bastian Timo , Seger Brian , Hansen Ole , Chorkendorff Ib , Kemppainen Erno , Halme Janne , Lund Peter 
Published: February 2020

Recent years has seen enormous and impressive progress in the search for non-precious hydrogen evolution reaction (HER) catalysts for both electrolysis and photoelectrochemical water splitting (PEC) with the molybdenum sulfide– and the cobalt phosphide families of HER catalysts showing great potential [1]. Despite the progress, no non-precious catalyst which matches platinum in HER performance has yet been found. To a large degree, the hunt for non-precious HER catalysts is motived by the notion that the physical scarcity and high price of platinum precludes it from usage on the terawatt scale. Using numerical modelling supported by benchmarking experiments on very well-defined platinum-based PEC electrodes we demonstrate that platinum in principle offers sufficiently fast kinetics to be useful on the terawatt level. As may be seen in the insert in figure 1 just 54 tons of platinum (which corresponds to ca. 30% of the global annual production [2]) would in principle be enough to support 1 TW of HER at a PEC current density of 10 mA/cm2 at a modest overpotential of 50 mV.[3] We discuss the platinum requirement under different assumptions and also the potential problems of using platinum in real-world PEC systems.
Refs
[1] P.C.K. Vesborg, et al., J. Phys. Chem. Lett., 6, (6) p. 951-957, (2015)
[2] P.C.K. Vesborg & T.F. Jaramillo, RSC Advances, 2, (21), p. 7933-7947, (2012)
[3] E. Kemppainen et al., Energy & Environmental Science, 8, p. 2991-2999 (2015)
Figure: Overpotential vs. of platinum loading for PEC-relevant current densities and (insert) total platinum requirement to implement 1 TW (average power, at a 15% capacity factor) of PEC hydrogen production.

Figure 1
Development of Efficient, Stable and Intrinsically Safe Photoelectrochemical Solar-Hydrogen Prototypes
Authors: Xiang Chengxiang("CX") 
Published: February 2020

Artificial photosynthesis offers an attractive way to store solar energy in the form of fuels at the terawatt scale. An integrated solar-driven water-splitting cell has great promise in producing cost competitive, renewable hydrogen from the sun at large scale. The key performance requirements for such an integrated system include high conversion efficiency, long-term stability, earth-abundant materials and product separation for safety. While significant advances in photoelectrochemical water-splitting have been made in the materials discovery, component integrations, cell designs and full device demonstrations, proof-of-concept demonstrations in literature have failed to meet all four requirements simultaneously.
Recently, in Joint Center for Artificial Photosynthesis (JCAP) at Caltech, we have developed several high efficiency photoelectrochemical water-splitting prototypes based on InGaP/GaAs tandem photoabsorbers. The custom designed tandem stack produced optimal current voltage characteristic for direct solar-hydrogen generation. I will briefly talk about the development of both photocathode-based and photoanode-based prototypes that were designed and constructed for different electrolyte and operational conditions. I will focus on one specific prototype design that employed a bipolar membrane. The integrated photoelectrochemical cell showed spontaneous solar-driven water splitting at the 1 sun illumination and operated sustainably under a steady-state pH gradient. A record performance combination (>10% efficiency, >100 hours stability, full product gas separation and all earth-abundant electrocatalysts ) in a relatively large area (> 1 cm2) photoelectrochemical system has been achieved. The performance of prototypes under the realistic outdoor conditions will also be discussed.
The Effect of Anisotropic Physical Properties of Cu(InxGa1-x)(Se,S)2 (CIGS) Single Crystal Photocatalysts on Water Splitting
Authors: Frick Jessica Jane , Kushwaha Satya K , Krizan Jason W , Baruch Maor , Cava Robert J , Bocarsly Andrew B. 
Published: February 2020

The photoelectrochemical splitting of water to produce H2 and O2 is an attractive process for the large-scale production of clean, recyclable H2. The field of solar water splitting has gradually divided into either using conventional materials as thin films with stabilization layers or developing new materials that are themselves stable in electrolyte solutions under illumination. Divergent from these paths, we are investigating semiconductors in their single crystal form in order to take advantage of the physical properties unique to crystalline materials that are likely to cause a significant impact on photoactivity. Due to crystalline anisotropy, the crystallographic orientation of the exposed electrode surface is anticipated to affect the overall efficiency of the photocatalytic water-splitting process and the photostability of the material.
Moderate band gap ternary chalcopyrites are a promising class of semiconductors for photoelectrochemical water splitting. Specifically, copper-indium-gallium dichalcogenides (diselenide or disulfide) [Cu(InxGa1-x)(Se,S)2]—abbreviated as CIGS—appear interesting due to their ideal, tunable light-absorption properties and band edge positions. To date, CIGS research has focused solely on thin film of nanoparticle materials. Electrodes based on these materials have demonstrated activity as photocathodes in photoelectrochemical cells (PEC) for water splitting.
The role of crystallographic quality of CIGS in single crystal form has yet to be examined in PEC water splitting studies. The tetragonal crystal lattice structure of CIGS (Figure 1) gives a degree of asymmetry to the crystals, generating anisotropic properties in different lattice planes. Anisotropic variability has been shown to affect the optical, magnetic, and thermal expansion properties of CIGS. These differences in physical properties are expected to generate a crystal face dependence on the photoelectrochemical response of CIGS. In this presentation, we will report on the solid-state synthesis of oriented CIGS single crystal electrodes, along with the effects of crystallographic orientation on the efficiency of water-splitting.

Figure 1: Tetragonal crystal structure of CIGS chalcopyrite semiconductors. View along the c-axis (left); view along the a-axis (right). Cu atoms are copper, In/Ga atoms are teal, and Se/S atoms are yellow.

Figure 1
Interfacial Charge Dynamics of in2S3-Decorated TiO2 Nanowires
Authors: Hsieh Ping-Yen , Hsu Yung Jung 
Published: February 2020

Ultrafast laser spectroscopy such as time-resolved photoluminescence is a powerful tool to retrieve dynamical information on the early steps of charge carrier transfer. In the past few years, considerable efforts have been devoted to studying interfacial charge dynamics of semiconductor heterostructures and realizing their implications in the photocatalytic processes. On the other hand, electrochemical impedance spectroscopy has demonstrated practical capability of revealing the reaction kinetics at the electrode/electrolyte interface, which is important for estimating the electrode efficiency for electrochemical reactions. Here we present the interfacial charge dynamics for In2S3-decorated TiO2 nanowires, which represent a typical TiO2-based type-II heterostructure system that has been widely used for photoelectrochemical water splitting. Because of the band alignment, the photoexcited electrons would preferentially transfer from In2S3 to TiO2, while the photogenerated holes were transported in an opposite direction from TiO2 to In2S3. Time-resolved up-conversion photoluminescence and electrochemical impedance spectroscopy were utilized to monitor the generation of charge carriers, the subsequent relaxation and recombination processes as well as their further involvement in the water splitting reaction. A temporal scheme which depicts the carrier lifetime at each of the above deactivation pathways was established to fully understand the fate of charge carriers within the In2S3-decorated TiO2 samples. The in-depth understanding of charge carrier dynamics can boost insights into the factors dictating the overall carrier utilization efficiency, which is imperative to the intelligent design of optimalsemiconductor nanostructures for photoelectrochemicalapplications.