bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using Soft X-Rays and Electrons to Determine the Chemical and Electronic Structure of Semiconductors for Solar Water Splitting
Authors: Heske Clemens 
Published: February 2020

In order to maximize the contribution of solar energy to the future global energy portfolio, it is important to optimize the performance, stability, and cost of the devices involved in solar energy conversion (in particular solar water splitting). For that purpose, novel material classes are being exploited, invariably leading to the investigation and use of complex, often ternary or even multinary compounds.
The purpose of this talk is to demonstrate how a tool chest of soft x-ray and electron spectroscopies (in particular using high-brilliance synchrotron radiation) is uniquely suited to unravel the electronic and chemical properties of surfaces and interfaces of such materials, and how an understanding on such fundamental level can lead to increased performance. It will be shown how photoelectron spectroscopy (PES), x-ray-excited Auger electron spectroscopy (XAES), inverse photoemission (IPES), x-ray emission spectroscopy (XES), and x-ray absorption spectroscopy (XAS) can be suitably combined to derive band gaps, study local chemical bonding and electronic level alignment, and derive insights into chemical stability.
As examples, WO3- and GaInP2-based water-splitting devices will be discussed, and Cu(In,Ga)(S,Se)2 solar materials will be used to further illustrate pertinent aspects of the experimental tool chest.
Artificial Photosynthesis Using Iron Foam Photoanodes Coated with Catalytic Graphene-Manganese Porphyrin Self-Assembled Structures
Authors: Kaplan Amir , Korin Eli , Bettlehiem Armand 
Published: February 2020

Photoelectrochemical (PEC) water splitting, also called artificial photosynthesis, is one way to produce clean hydrogen using solar energy to split water into oxygen and hydrogen gases. The main challenge in PEC field deals with low current densities of the photoanode. Today's conventional approaches to increase current densities are directed towards improving semiconductor (e.g. hematite) properties, increasing the active surface area of the electrode and adding known water splitting co-catalysts.
The present work deals with the characterization of porous iron foams as photoanodes, instead of the mostly used planar transparent electrodes. The iron foams can be coated by a thin hematite layer by a simple heat treatment procedure. The performance of these electrodes is significantly increased by doping with silicon, Co(II) ions, and macrocyclic catalysts. The iron foams electrodes yield efficient photocurrents for water splitting in the range of ~ 0.2-0.4 mA/cm2 at 1.23 V vs. NHE.
Anionic carboxylic-rich graphene oxide (CGO) and cationic Mn(III) tetrakis(N-Methyl-4-Pyridinium) porphyrin (MnTMPyP) form self-assembled leaf-like structures. These are obtained through electrostatic and π-π stacking interactions, as indicated by the red shift of the metalloporphyrin Soret band throughout the 6-12 pH range. When exploited for the photoelectrochemical oxidation of water, CGO-MnTMPyP films on iron/hematite foams exhibit substantial activity as evidenced by the current density (0.54 mA/cm2 at 1.23 V vs. NHE) and IPCE (9.0 % at 1.43 V vs. NHE) measured at pH 10.
Electrophoretic Deposition of NiCo2S4 Thin Film As a Catalytic Material for Dye-Sensitized Solar Cells
Authors: Chou Shu-Wei , Lin Jeng-Yu 
Published: February 2020

Dye-sensitized solar cells (DSCs) have become one of the most promising photovoltaic devices due to their low cost, simple fabrication, and relatively high powerconversion efficiency.To reduce the cost of DSCs, it is necessary to find out high-efficiency and low-cost alternatives to replace the conventional noble Pt counter electrode (CE). Among inorganic compounds, transition metal sulfides, such as CoS, NiS,MoS2 and WS2, have attracted extensive attention dueto their excellent electrocatalytic activity for I3
− reduction.
In this study, NiCo2S4 was firstly synthesized via a facile solvothermal method and then subjected to electrophoresis onto a fluorinated tin oxide (FTO) glass substrate. The resultant NiCo2S4 CE demonstrated both high transmittance (>75%) at visible wavelengths and improved electrocatalytic activity, while the DSC based on the transparent CE still achieved an impassive cell efficiency of 6.14%.Moreover, the NiCo2S4 films deposited by the facile electrophoretic deposition has the following benefits,including low temperature, high depositionrate, controllable thickness, great uniformity, scalable production, and without using any organic binders.Therefore, the DSC assembled withthe transparent NiCo2S4 CE could be a promising candidate as Pt-free CE for DSCs application.
Novel Photoelectrodes and Noble Metal-Free Catalysts for Light-Driven Water Electrolysis
Authors: Fiechter Sebastian 
Published: February 2020

The generation of fuels from sunlight and water is considered as a task of paramount importance for a sustainable energy supply in the future. Decomposition of water by a photoelectrochemical process is a possibility to harvest solar energy in the form of hydrogen in a large scale. For this purpose, a membrane can be used which -when immersed in an aqueous electrolyte and illuminated by sunlight- will be able to split water into hydrogen and oxygen. Such a device is frequently addressed as artificial leaf. From an eco­nomic and environmental point of view this device should comprise of cheap, abundant and non-toxic elements featuring a Solar-to-Hydro­gen (STH) efficiency > 10% and generating hydrogen at a price of ~3 €/kg H2.
In our lab two approaches have been pursued to realize artificial leaf type structures:
o triple junction thin film a-Si/µc-Si solar cells in superstrate geometry with integrated catalysts [1],
o tandem junction solar cells combined with novel semiconducting ternary metal oxide anodes [2].
As photoanode materials Fe2WO6 and BiVO4 are under investigation. Their performances have shown considerable improvement with respect to their photovoltage and their photocurrent densities when synthesized using sol-gel and spray pyrolysis. To lower the costs of the device, platinum was replaced by carbon supported MoS2 nanoparticles as hydrogen evolving catalyst. Deposited as a blend with PEDOT:PSS on the backside of the solar cell, a SHE yield of 3.7% was achieved. RuO2 was replaced by manganese and cobalt oxide thin films, respectively.
References:
[1] Diana Stellmach, Peter Bogdanoff, Onno Gabriel, Bernd Stannowski, Rutger Schlatmann,
Roel van de Krol, Sebastian Fiechter; FORMATEX 2013, 880-886.
[2] Fatwa F. Abdi, Lihao Han, Arno H.M. Smets, Miro Zeman, Bernard Dam, Roel van de Krol, NATURE COMM. 2013, 4: 2195, DOI: 10.1038/ncomms3195.
[3] Eric L. Miller, Björn Marsen, Daniela Paluselli, Richard Rocheleau, Electrochemical and Solid- State Letters 2005, 8: A247.

Figure 1
Pt- and TCO-Free Flexible Counter Electrodes for Dye-Sensitized Solar Cells
Authors: Lin Jeng-Yu , Wang Wei-Yan , Chou Shu-Wei 
Published: February 2020

Dye-sensitized solar cells (DSSCs) have attracted extensiveattention as low cost, easy manufacturingprocess and acceptedphotovoltaic performance. Typically, a DSSC includes a dye-sensitizedsemiconductor photoanode, an I−/I3
− redox electrolyte and a Pt counter electrode (CE). As a crucial component in DSSCs, the basicfunctions of a CE are to increase the transfer of the electrons from the external circuit back to the electrolyte and accelerate the reduction reaction from I3
−to I−.Nevertheless, limited resources and high prices would restrict the application of Pt thin film coated on a transparent conducting oxide (TCO).To solve this issue, several alternatives have been proposed to serve as TCO-freeand Pt-free CEs for DSSCs.
In this study, Ni3S2/Ni−P hybrid film coated on a flexible polyimide (PI) substrate was employed as a TCO-free and Pt-free flexible CE for DSSCs. The bilayer Ni3S2/Ni−P hybrid film was deposited on a polyimide (PI) plastic substrate by using a series of chemical/electrochemical treatments/processes. As a result, the DSSC assembled with the Ni3S2/Ni−P coated PI flexible CE displayed an impressive photovoltaic conversion efficiency of 6.28%.
Understanding Transport Phenomena in Perfluorosulfonic-Acid Membranes
Authors: Weber Adam Z , Gostick Jeff T. , Kusoglu Ahmet , Crothers Andrew 
Published: February 2020

One of the keys to optimizing polymer-electrolyte-fuel-cell performance is understanding its transport phenomena. This is especially important for the proton-exchange membrane, which helps to control the water management within the cell, an integral aspect for optimal cell performance. Typical fuel-cell membranes are perfluorosulfonic-acid based and are essentially random copolymers that phase separate into hydrophilic domains for water and ion movement supported by a hydrophobic backbone phase.
We have previously shown that water transport and uptake at the nano- and macroscale is similar and relatively fast in membranes, especially at higher humidities.1,2 Once water crosses the membrane interface, time-resolved studies show that changes at the nano and macroscale scales occur almost simultaneously. Unlike water incorporation, proton conduction depends not just on the domains but also their interconnectivity. Time-resolved studies such as that in Figure 1, show that unlike the water incorporation, there is more of a time delay due to reorientation of the domains and the transport pathways. In this talk, such issues will be discussed.
In particular is the need to explore the structure-function relationships for the transport properties and the critical aspects that the membrane interface plays in controlling transport. In addition to experimental results, a model methodology will be presented to explore proton conductivity. In the model, we propose a macroscopic treatment that utilizes data on the nanoscale relating to membrane morphology and physically relevant phenomena,3 but in a framework that still allows for easy incorporation into cell-level fuel-cell models. Extensions of the analysis and phenomena to the thin-film regime, which is critical for fuel-cell catalyst layers, will also be presented.
Acknowledgements
We thank Steve Hamrock, Mike Yandrasits, and Greg Haugen at 3M for providing membranes and discussion; This work made use of facilities at the Advanced Light Source (ALS), supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy. This work was funded by the Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231.
References
1 Gi Suk Hwang, Dilworth Y. Parkinson, Ahmet Kusoglu, Alastair A. MacDowell, and Adam Z. Weber, ACS Macro Letters, 2, 288-291 (2013).
2 Daniel S. Hussey, Dusan Spernjak, Adam Z. Weber, Rangachary Mukundan, Joseph Fairweather, Eric L. Brosha, John Davey, Jacob S. Spendelow, David L. Jacobson, and Rodney L. Borup, J. Appl. Phys., 112, 104906 (2012).
3 Ahmet Kusoglu, Suchol Savagatrup, Kyle T. Clark, and Adam Z. Weber, Macromolecules, 45 (18), 7467-7476 (2012).

Figure 1
Structure and Transport Properties of Ionomer Thin Films in Membrane-Electrode Assemblies
Authors: Elliott James A 
Published: February 2020

Perfluorosulfonic acid (PFSA) electrolyte membranes, such as Nafion, are widely employed in fuel cells due to their high proton conductivity combined with excellent chemical and thermal stability. However, the structure and ion transport properties of such materials differs markedly from those of the bulk polymer when confined to thin films, as commonly found in the catalyst layers of membrane-electrode assemblies (MEAs). Furthermore, the chemical nature of adsorbing substrate, whether metal catalyst or carbon electrode, also has a large influence on the structure and properties.
In this presentation, I will present results from density functional theory (DFT) and dissipative particle dynamics (DPD) simulations of model MEA systems in which the distribution of water and ionic groups at the interface in nanoscopic channels are compared with those in bulk membrane [1]. The results show that the structure of thin (5-10 nm) layers of PFSA membranes is quite different to that in bulk, and may play a key role in controlling performance of MEAs. In particular, the surface coverage of sulfonic acid groups is examined as a function of substrate hydrophilicity, hydration level and equivalent weight of ionomer. The results demonstrate that the anomalously voltage losses that occur at low catalyst loadings may be due in part to reduced effectiveness of proton transport in the ionomer films.
[1] J.A. Elliott, D. Wu, S.J. Paddison and R.B. Moore, Soft Matter, 7, 6820-6827 (2011).
What Determines the Detection Limit during Impedance Biosensing?
Authors: Suni Ian Ivar 
Published: February 2020

Impedance biosensors have been widely studied for applications to biomedicine, environmental monitoring, food, and agriculture. The most common format for AC impedance biosensors involves surface immobilization of an antibody, receptor protein, DNA strand, or other species capable of bio-recognition, and AC impedance detection of the binding event.
For an electrode coated with a polymer film, electron transfer to a redox probe such as Fe(CN)6
3-/4- is essentially an electron tunneling process, so one expects exponential decline in the rate of electron transfer (kET) with film thickness (x) according to the equation below, where α is a constant for a given redox couple and l is the Marcus reorganization energy. This relationship has been quantified most accurately through studies of Au-thiol self-assembled monolayers (SAM) of variable chain length. Therefore, fundamental electrochemistry predicts that the detection limit should decline with increasing analyte molecular weight. However, this functional dependence is complicated, since it is related to the different between two terms that depend exponentially on film thickness.
Literature reports of detection limits during impedance biosensing will be summarized and discussed. Our results for impedance biosensing as a function of analyte molecular weight will also be discussed for impedance biosensing of peanut protein Ara h 1, cortisol, and endocrine-disrupting chemicals such as norfluoxetine and BDE-47. In addition, detection of BDE-47 using an alpaca single domain antibody results in a lower detection limit (0.79 ng/ml) than use of a rabbit polyclonal antibody (1.3 ng.ml). Possible electrostatic effects on detection limit are discussed through the use of oppositely charged Fe(CN)6
3-/4- and Ru(NH3)6
3+/4+ redox probes.

Figure 1
Surface Plasmon Resonance (SPR) of Reusable DNA LOOP Formation Dynamics
Authors: Yang Fuling , Arugula Mary , Somasundaram Subramaniam , Easley Christopher J , Shannon Curtis , Simonian Aleksandr 
Published: February 2020

Thiol-terminated single-stranded DNA (SH ss-DNA) monolayer assembly on gold as a probe is a significant model for various biosensors. In electrochemical proximity assay (ECPA), SH ss-DNA with complementary DNA loop moves a methylene blue (MB)-conjugated oligonucleotide (MB ss-DNA) close to a gold surface, which forms a DNA loop like structure, for transferring electron when target protein is present. After treatment of urea in DI water, the MB ss-DNA and DNA loop dissociate from the DNA loop like structure for reusability. Surface plasmon resonance (SPR) is a powerful optical technique for studying dynamic matrix of affinity biosensors.
In this study, we first confirmed DNA complementarities in flow mode with surface plasmon resonance detection. SPR results showed discriminative refractive angle change (DRA) in each DNA hybridization. However, the loss in DNA loop structure (SH-ssDNA or DNA loop) showed inconspicuous sensogram. Furthermore, we studied the effects of free thiols, which is a result of cleavage of disulfide precursors by reductant, in SH ss-DNA monolayer assembly on gold surface. Comparison of DRA in pure SH-ss DNA and non-purified SH-DNA in several concentrations showed free thiols can compete with SH-ss DNA on gold surface. DNA loop and MB ss-DNA added to two solutions is used for double confirmation of the recognition event. Mixture of different ratios of SH-ss DNA and free thiols were used to further study the competition between SH-ss DNA and free thiols. Moreover, we investigated reusable DNA Loop formation capable of several uses in simple matrix. Urea dissolved in DI water was utilized to dissociate DNA loop and MB ss-DNA from DNA loop-like structure. Optimization of concentration and pH of urea were performed. Study dynamics of this reusable DNA loop structure can improve sensitivity and feasibility of ECPA-based marker.
Development of Electrochemical Aptamer-Based Biosensors for the Detection of Hormonal Contaminants in Water
Authors: Contreras Jiménez Gaston , Eissa Shimaa , NG Andy , Zourob Mohammed , Siaj Mohamed 
Published: February 2020

Endocrine disrupters (EDs) are compounds that specifically interfere with the normal functions of the body’s endocrine system (system of glands for hormonal secretion) by causing adverse effects in both human and wildlife. Therefore, routine, sensitive, reliable and cost effective detection methods for EDs are highly demanded. In this work we present the selection and characterization of ssDNA aptamers that exhibit high affinity, specificity and sensitivity to progesterone (P4), 17b-estradiol (E2) and, norethisterone (NET). The aptamer selection was conducted by in vitro selections by incubating a highly diverse ssDNA library of about random 60mer sequences with the target analyte. After 15 cycles of selections, the enriched aptamers pool was cloned and sequenced. The dissociation constants (KD) of the selected aptamers determined by fluorometry and by electrochemical impedance spectroscopy (EIS) methods are in the subnanomolar order. Cross-reactivity tests for each aptamer demonstrated the high specificity to their target analyte. In addition, circular dichroism (CD) spectroscopy measurements of the selected aptamers for progesterone showed a marked conformational change upon binding the target analyte. This change in the conformation was exploited to design a biosensing platform to generate a measurable signal after binding the specific analyte by following the redox process of a couple composed for [Fe(CN)6]3-/4-. For first time, an impedimetric aptasensor for progesterone detection was developed with limit of detection of 0.90 ng/mL. We believe, based in our finding, that the continuous selection of high affinity aptamers for other EDs and their integration in a biosensing platform will facilitate the routine monitoring of EDs in environment as well as clinical and medical diagnosis purposes.

Figure 1
MWCNTS/Nickel Oxide Nanocomposite Supercapacitor Made from Two Electrode Coin Type Cells
Authors: Adekunle Abolanle Saheed , Mamba B. B. , Agboola B. O. , Oluwatobi O. S. , Ozoemena Kenneth I. , Ebenso Eno E 
Published: February 2020

Studies have shown that carbon nanotubes-metal oxide (CNT/MO) nanocomposite modified electrodes exhibited huge capacitive current in some electrolytes [1-6]. Therefore, it becomes imperative to establish the charge storage properties of these materials as a potential source for energy generation in acidic and neutral medium since most reported work has been conducted in an alkaline environment. In this work, supercapacitive property of synthesised nickel oxides (NiO) nanoparticles integrated with multi-walled carbon nanotubes (MWCNT) in an acidic medium using a two-electrode coin cell type supercapacitor was investigated. Successful formation of the MWCNT-NiO nanocomposite was confirmed with techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The supercapacitive behaviour of both the symmetry and the asymmetry MWCNT-NiO based supercapacitor in 1 M H2SO4 and 1 M Na2SO4 electrolytes was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic constant current charge-discharge (CD) techniques. There was a good correlation between the CV and the CD specific capacitance (SC) values for the asymmetry supercapacitor. Asymmetry supercapacitor (MWCNT-NiO|H2SO4|MWCNT) gave the highest SC value of 925.9 mFcm-2 (53.9 F g-1) and energy deliverable efficiency of 101.0±8.1%. High SC values which are higher than most of those reported in literature were obtained. The electrodes demonstrated high stabilities with no significant changes in SC values over 1000 cycles.

References:
1. A.S. Adekunle, K.I. Ozoemena, Electrochim. Acta 53 (2008) 5774.
2. A.S. Adekunle, K.I. Ozoemena, J. Solid State Electrochem. 12 (2008) 1325.
3. B.E. Conway, Electrochemical Super Capacitors, Kluwer Academic/Plenum Publishers, New York, 1999.
4. M. Winter, R.J. Brodd, Chem. Rev. 104 (2004) 4245.
5. Y.H. Lee, K.H. An, J.Y. Lee, S.C. Lim, Encycl. Nanosci. Nanotechnol. 1 (2004) 625.
6. E. Frackowiak, F. Beguin, Carbon 40 (2002) 1775.
Novel 3D Nanocarbon Electrodes for High-Rate Li-Ion Batteries
Authors: Wang Huan , Xie Jingyi , Follette Marissa , Amama Placidus B 
Published: February 2020

Portable electronic devices are negatively impacted by power density limitations of current Li-ion batteries (LIBs). Architectures or materials for faster ion and electron transport are required. Graphene-based electrodes with a 3D hierarchical structure have shown promise in LIBs due to their short ion diffusion distance, excellent electrical conductivity and high surface area. However, techniques for fabricating such hierarchical nanostructures with textural properties that can be easily tailored are still complicated and not fully developed. In this work, a low cost, green, facile, controllable and scalable approach for the fabrication of 3D hierarchical graphene-based electrodes is proposed. The 3D hierarchical structures with adjustable pores and nanowrinkles are prepared from graphene oxide or chemically functionalized graphene sheets via a wet chemical method using polymeric micro-gels as the template. The resulting 3D graphene electrodes have been used as a model 3D electrode system to establish correlations between the 3D properties (surface chemistry, defect density and textural properties) and the LIB performance (rate capability, energy capacity and durability).
Fabrication of Multiwalled Carbon Nanotube-Wrapped Ultrathin SnS2 Nanoplates and Their Superior Li-Ion Intercalation Performance
Authors: Guan Dongsheng 
Published: February 2020

Two-dimensional ultrathin SnS2 nanoplates enwrapped into a multiwalled carbon nanotube (MWCNT) network are synthesized by a facile and one-step hydrothermal method with SnCl2∙H2O and thiourea as reactants and sodium dodecylbenzenesulfonate as surfactant. The highly dispersed carbon nanotubes in ethanol solution are found to reduce the thickness of SnS2 nanoplates during their growth and embed them into an interconnected network finally. In lithium-ion battery studies, the electrode fabricated from the SnS2 nanoplate/MWCNT hybrid material delivers excellent lithium-ion intercalation properties, with larger specific capacity, higher rate capability and better cycling stability than that of electrode made of bare SnS2 nanoplates. The improved electrochemical performance is ascribed to a fact that this porous, hybrid architecture effectively accommodates the volume change of SnS2 during charge–discharge to maintain structural stability, facilitates the easy access of electrolyte to the huge surface of nanoscale active materials, and also provides a continuous conductive network to significantly enhance the charge transfer kinetics at electrode.

Figure 1