bluuebunny/crossref_metadata_2025_split huggingface dataset:
Splitting Water from Vapor Feeds: Towards Air-Based Solar-Hydrogen Generators
Authors: Modestino Miguel A. , Hashemi Mohammad H. , Gregory Daniel , Moser Christophe , Psaltis Demetri 
Published: February 2020

Electrochemical water-splitting devices can contribute to increase the share of renewable sources in today’s energy landscape. Simplifying the operation of state-of-the-art electrolysis systems could help drive their large scale deployment. One alternative for the simplification of electrolyzers is the implementation of systems that can operate directly with water vapor feeds. Operation under vapor conditions brings with it several advantages: a reduced water-splitting potential, the elimination of catalysis limitations from bubble formation, and a slow-down of the degradation processes of the materials involved in the water-splitting process. In this study, we introduce a microstructured device that can produce hydrogen from humid ambient air streams.1 The device is composed of interdigitated microelectrodes that are covered by a thin ionomer film (Nafion®) (< 1 µm). Water diffuses through this film and is oxidized at the anode interface to generate oxygen and protons. Protons then migrate through the film towards the cathode side and are reduced to produce hydrogen. This presentation will provide insights into the multiple transport and electrochemical processes taking place inside of the ionomer and that affect the overall device performance. The effects of parameters such as electrodes dimensions, interelectrode separation, electrocatalysts selection and ionomer processing were studied, and their effects in the operation of the device will be discussed. We demonstrate that large ionic resistances in the devices limit the current densities achievable, and that minimizing the pathways for proton transport can result in current densities higher than 10 mA/cm2at 1.8 V. Lastly, strategies towards the integration of these air-based electrolysis components into solar-hydrogen generators will be presented.
1. M. A. Modestino, M. Dumortier, M. Hashemi, S. Haussener, C. Moser and D. Psaltis, Lab on a Chip, 2015, 15, 2287-2296.

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Bipolar Electrodeposition: A Wireless Method for Deposition of Electrocatalysts Onto Semiconducting Particles
Authors: Gaieck William , Tkacz Kevin , Yaghoubi Houman , Ardo Shane 
Published: February 2020

Global climate change due to combustion of fossil fuels and a lack of grid-scale energy storage will continue to negatively affect our environment and impede our ability to diversify energy sources and increase energy independence. However, if we can harness the power of the Sun, much like plants, then we can achieve a sustainable, net carbon neutral future with inherent energy storage capacity in chemical bonds.
Solar photoelectrochemical water splitting produces H2, which can be used as a fuel. Proposed technologies to achieve this photochemistry typically use either a separate photovoltaic and electrolyzer, or an integrated wafer-based system. Unfortunately, these systems are costly, relying on relatively large quantities of precious metal electrocatalysts and intensive fabrication/processing methods. In contrast to these designs is the particle slurry reactor where the hydrogen evolution reaction and the oxygen evolution reaction are separated into different compartments, connected ionically and electronically via a solution redox shuttle, and stacked optically in series. This design is predicted to be cost-competitive with hydrogen produced from fossil fuels on an energy equivalent basis.
Herein, we report on the reductive and oxidative depositions of electrocatalysts (e.g. Pt, Au, CoOPi, NiMo, and NiFe(O)OH) on state-of-the-art semiconducting nanoparticles (e.g. TiO2, WO3, and BiVO4). The unique aspect of this work is that this deposition occurs in the bulk without physically contacting the particles with electrodes. Instead, bipolar electrochemistry is used to electrodeposit these catalysts, which is a wireless, non-contact technique. After deposition, the composite materials were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD) to determine the efficiency of the deposition process. Using a variety of electrochemistry techniques, electrodes of these materials will be fabricated and evaluated for the efficiency for either the hydrogen or oxygen evolution reaction. Deposition of electrocatalysts was controlled by changing the particle and electrolyte concentrations, the solution viscosity, and the applied bias. We show that these controls allow tuning of the morphology, geometry, and material deposition of the electrocatalysts. This work expands on the robustness of bipolar electrochemical techniques and suggests that a flowable bipolar electrochemical system may allow more control and flexibility of electrocatalyst deposition than other bulk deposition methods. This work was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Incubator Program under Award No. DE-EE0006963.
(Invited) Applications of Multivariate Methods in the Study of Ionomer Properties
Authors: Korzeniewski Carol , Zhang Pei , Liang Ying 
Published: February 2020

Multivariate data analysis methods are being applied in conjunction with vibrational spectroscopic measurements to gain insights into structure and physical properties of ionomer materials. Infrared and confocal Raman spectroscopy techniques are being adapted to investigate (i) fluorinated ionomer standards that span a range of equivalent weight and (ii) membrane samples with varying tensile properties. Partial least squares (PLS) modeling applied to mid-infrared spectral data sets measured using the attenuated total reflection (ATR) technique is robust in predicting ionomer equivalent weight from measurements on calibration samples. The experimental approach, statistical uncertainties and extension to confocal Raman experiments will be discussed.
In relation to membrane structural and tensile properties, vibrational spectra that follow transitions between dispersion, gel and solid membrane ionomer forms are being scrutinized. Least-squares modeling and principal component analysis (PCA) used in combination enhances the ability to resolve spectral features associated with molecular components of the sample that evolve during processing (Figure 1) and to quantitatively track changes in composition over time. Figure 1 shows results from confocal Raman tracking of aqueous Nafion ionomer dispersion through a gel phase. PCA and least-squares modeling were applied to data within the shaded region to extract the indicated spectral components. For membrane processed under different thermal treatments, PLS regression is being applied to examine the correlation between tensile strength and molecular scale structure probed by vibrational spectra.

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(Invited) Metal Hydride-Air Batteries for Large-Scale Energy Storage Systems
Authors: Bugga Ratnakumar V , Fultz Brent , Addison Dan 
Published: February 2020

The poor safety behavior of Li-ion batteries necessitates complex charge electronics, elaborate thermal management and suitable mechanical reinforcements. These would result in reduced system-level energy densities, compared to the cell-level values, and also higher battery costs. In contrast, the aqueous systems, especially the metal-air systems that can provide high specific energies and energy densities look more appealing due to their inherent safety. Under an ARPA-E sponsored program, we (JPL, Caltech and Liox) are developing low cost and safe rechargeable metal-hydride/air batteries with high energy densities (200 Wh/kg and 400 Wh/l at cell level) for electric vehicle applications. Our effort is focused on developing: i) new metal hydride alloys with higher hydrogen absorption capacities, ii) stable low-cost electro-catalysts for air cathodes, iii) new cell and stack designs and iv) simpler water management schemes.
We have been developing metal hydride alloys of vanadium-based quaternary BCC alloys (Ti-V-Ni-Cr) as anode materials, low-cost perovskite-based and Ni-Fe-Co layered double hydroxide catalysts for oxygen electrodes, and cell and system designs that minimize thermal and concentration gradients. In this paper, we will describe some of our recent results on this technology.
Vanadium Sulfate As New Electrode Material for Na Ion Batteries
Authors: Pralong Valerie , Gnanavel Muthaiyan , Caignaert Vincent , Raveau Bernard , Lebedev Oleg 
Published: February 2020

The design of new materials that provide high energy densities and long cycle life together with being economic and environmental benign is crucial for the energy storage. Therefore, the soft chemistry used to prepare the original frameworks, new structures is in perfect appropriateness with such a target. Our research is focused on the synthesis by soft chemistry of new “metastable” frameworks with large tunnels or layered structures at low temperature. We will discuss on our strategies to generate original framework showing ionic conductivity. The first approach is based on topotactic reactions starting from existing ionic conductors with a compact anionic framework [1]. In this case, we will show that the lithium/sodium insertion leads to new rock salt type structure. The second approach is related to polyanionic frameworks [2]. In order to favor reactivity, we are using protonic materials containing transition elements with adequate redox potential (Fe, Mn). We will show for example that lithium or sodium insertion into the jarosite hydroxysulfate phase NaFe3(SO4)2(OH)6 leads to an amorphous phase Na3Fe3(SO4)2(OH)6 which exhibits a reversible electrochemical sodium intercalation/deintercalation through a solid solution-like process, leading back to the jarosite NaFe3(SO4)2(OH)6, at 2.72V and a capacity of 100 mAh/g at C/20. This unique topotactic reaction between an amorphous and a well crystallized phase is interpreted on the basis of the formation of an inorganic polymer and will be discuss in the presentation.

V. Pralong, V. Gopal, V. Caignaert, et al., Chem. Mat. Com., 2012, 24, 12; V. Pralong, Progress in Solid State Chem., 2009, 37, 4, 262-277; V. Gopal, V. Pralong, et al., Electrochem. Com., 40, 100-102, 2014; V. Pralong et al., Inorg. Chem., 53, 522, 2014

M. A. Reddy, V. Pralong, V. Caignaert, et al., Electrochem. Com., 2009, 11 1807; V. Pralong, V. Caignaert, B. Raveau, J. Mater. Chem., 2011, 21, 12188; M. Gnanavel et al., Chem Mater., 26, 4521, 2014
Study of Electrodeposited Zinc Morphology in Rechargeable Alkaline Batteries
Authors: Wei Xia , Couzis Alexander , Banerjee Sanjoy 
Published: February 2020

Rechargeable zinc-nickel flow-assisted batteries are attractive in applications like frequency regulations, UPS inverters and hybrid electrical vehicles, etc[1] due to their advantages, such as, being cheap, capable of rapid charging and discharging and high energy density. However, the challenge that rechargeable zinc-anode batteries are facing is short lifespan time due to non-uniform morphology of zinc deposition during charging, hydrogen evolution that compromises energy efficiency and zinc corrosion during battery resting, which leads to further capacity loss[2].
We developed an indicator that monitors the transition of zinc morphology during battery charging[3]. Zincate concentration in the electrolyte, flow velocity and current density were varied over a wide range in the experiments. The results from SEM and 3D X-ray computer tomography (figure 1) show that the ratio between the effective current density and the limiting current density (current density ratio), which is directly related to the zincate concentration at the electrode surface, determines the zinc morphology.
Furthermore, we investigated the causes of transition of zinc morphology. Compact zinc deposits are found to have a fine-grained, bright finish and the highest anodic efficiency (figure 2)[4]. Electrochemical impedance spectroscopy (EIS) proves that compact zinc corresponds to the minimum in the half-cell resistance, indicating it is kinetically preferred for compact zinc to form. Preferred crystal orientations of compact zinc depositions make good agreement with the EIS results.
Anode substrate is a parameter that also influences the zinc morphology. We studied the effects of various novel metal substrates on zinc morphology over battery cycling. Results from electrochemical techniques, chemical characterization and cell cycling showed that Cu and Bi are promising anode substrates.
In order to alleviate the corrosion rate and increase the lifespan of zinc-anode batteries, we investigated the impacts of additives on zinc morphology and cell performance. Lab-scale cells have demonstrated more than 2000 cycles and large-scale cells (113Ah) have demonstrated more than 200 cycles (figure 4 and figure 5). The results indicate that the morphologies of zinc deposition with the presence of additives are finer and the battery performance is improved as well.
References:
[1] D.E. Turney, M. Shmukler, K. Galloway, M. Klein, Y. Ito, T. Sholklapper, J.W. Gallaway, M. Nyce, S. Banerjee, J. Power Sources 264 (2014) 49–58.
[2] Y. Ito, M. Nyce, R. Plivelich, M. Klein, D. Steingart, S. Banerjee, J. Power Sources 196 (2011) 2340–2345.
[3] Y. Ito, X. Wei, D. Desai, D. Steingart, S. Banerjee, J. Power Sources 211 (2012) 119–128.
[4] D. Desai, X. Wei, D.A. Steingart, S. Banerjee, J. Power Sources 256 (2014) 145–152.

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Flexible and Stretchable Supercapacitors from Carbon Materials
Authors: Zhou Yihao , Cao Changyong , Ubnoske Stephen , Henry Philemon A. , Parker Charles B. , Franklin Aaron , Glass Jeffrey T. 
Published: February 2020

Flexible and stretchable electronics have attracted increasing attention over the past decade. Compared with traditional electronics, which based on rigid silicon chips, flexible and stretchable electronics can conform to complex surfaces and sustain large deformations without sacrificing their performance. An important component of flexible or stretchable electronics is energy storage, such as supercapacitors or batteries. Existing stretchable supercapacitors are characterized by complicated fabrication processes, low stretchability and high cost, constraining their potential applications. Due to their electrical characteristics and large surface areas, carbon materials, such as activated carbon, carbon nanotubes, and graphene, have been investigated for supercapacitor applications. In this work, we report two new kinds of flexible and stretchable supercapacitors made from carbon nanotube and hybrid carbon materials using a facile and low-cost method.
Stretchable electrodes were developed using vertically aligned carbon nanotube (CNT) forests grown on a silicon substrate by PECVD. The CNT forests were transferred to a prestretched elastomer substrate using a dry-transfer method. The CNT electrodes can be biaxially stretched up to 300% while maintaining good electrochemical performance. The area specific capacitance is enhanced almost 10x to more than 20mF/cm2. CNT forests can form novel micro- and nano- patterns under uniaxial or biaxial prestrains, making it possible to use them as conductive hierarchical scaffolds for functionalization with pseudocapacitive materials, such as MnO2 for better performance.
Aerosol jet printing and self-organized origami were used to fabricate a stretchable RGO/CNT/PEDOT: PSS supercapacitor. The unique direct-printing method gives the supercapacitor outstanding mechanical properties. No delamination was observed at the interface between the printed film and the substrate during the large deformation process. The composite electrodes exhibited highly porous structures and high conductivity, which leads to good electrochemical performance: a large specific capacitance (150F/g), high rate capability (>95% at 5A/g compared to 0.1A/g), and high cyclability. Further, there was little performance degradation after hundreds of stretch-release cycles, indicating the excellent reliability of the stretchable devices.
Our designs and methods open a new way for fabricating future energy storage devices with high deformability, high performance and low cost.
Studies of Fundamental Charge Transfer Processes in Organic Radical-Containing Polymer Films Using Spectroelectrochemical Techniques
Authors: Hughes Barbara Katherine , Braunecker Wade A. , Johnson Justin C. , Ihly Rachelle , Gennett Thomas 
Published: February 2020

The electrochemical redox reaction of stable organic polymer materials with unpaired electrons is a relatively new and exciting area of battery research. Specifically, stable nitroxyl radical-containing polymers have displayed excellent characteristics as the cathode-active material and have presented themselves as a low-cost and environmentally friendly alternative to the current Li-ion battery technologies. However, with the advancement of organic-radical battery technology there is a lack of fundamental understanding of the dynamics of charge transfer processes, electronic and ionic, within organic radical-containing polymers. In order to elucidate these mechanisms further, we have conducted extensive spectroscopic and spectroelectrochemical investigations of macromolecular systems containing nitroxide radicals.
We have employed spectroelectrochemical experiments for our study of stable radical polymer systems whereby, kinetic information was determined, specifically rates of charge transfer and ion diffusion within our polymer systems. A key factor determining the success of such experiments is that the material of interest exhibits a strong absorption coefficient and allows for measurement in the concentration regime conducive for electrochemical studies (typically up to 10 mM). For this reason, of the available stable nitroxyl radical systems, we have chosen first to study the oxidation of a nitronyl nitroxide derivative. To simulate an electrode architecture, spectroelectrochemical studies were performed in the solid state, and the efficacy of charge transfer was investigated as a function of film thickness, counter-ion size, and radical polymer composition in “neat” polymer films. The addition of semiconducting carbon nanotubes at various loadings was also explored as changes to film conductivity has significant implications for rates of ion transport.
Influence of Nanostructured Carbon Supports on Nanocatalysts Towards Electrooxidation of Formic Acid for Direct Formic Acid Fuel Cells
Authors: Shanta Tamanna Ferdous , Miao Wujian 
Published: February 2020

Direct formic acid fuel cells (DFAFCs) have been reported as a prominent source of alternative green energy and solution to imminent energy crisis for the last two decades. The challenge to commercialize DFAFCs is mainly the utilization of cost effective, high performance and durable anodic catalyst for electrooxidation of formic acid (HCOOH). Low metal loading, high surface area, good electrical conductivity, excellent stability in acidic and alkaline media, and easy availability make nanostructured carbon supports attractive for fuel cell applications. We report here the comparative studies of three different carbon based support materials and their influence on catalytic activities towards the electrochemical oxidation of HCOOH using mono (20 wt% Pd) and ternary (10 wt% Pd-Ni-Co) composite nano-catalysts with commercial 20 wt% Pd/C (activated carbon, ~500 m2g-1). The nano-catalysts were synthesized using Pd2+, Ni2+ and Co2+ precursors using Vulcan-XC72 (250 m2g-1, <50 nm), Ketjen Black (1400 m2g-1) and graphite nano-particles (GNP) (~10 nm) support materials and NaBH4 as reducing agent. The electrochemical oxidation of HCOOH was conducted at a glassy carbon disk electrode (GCE, 3 mm diameter) pre-casted with 9 µL of each catalyst ink covered with 3 µL Nafion® polymer (5 wt%) in 0.50 M HCOOH-0.10 M H2SO4. The catalytic oxidation behavior of HCOOH of all the catalysts was compared using cyclic voltammetry. Multi-potential step chronoamperometry (CA) was utilized for stability tests. The catalytic behavior of all the ternary nano-catalysts is believed to be ascribed to the direct oxidation pathway of HCOOH as indicated by the oxidation peak potential of ~ -0.2 V vs Hg/Hg2SO4 (satd. K2SO4) reference electrode. In contrast, the synthesized mono catalysts and commercial Pd/C showed both direct and indirect oxidation pathways. The use of Ni and Co also showed synergistic effect as the HCOOH oxidation peak potential was shifted negatively by ~200 mV with respect to that of the commercial catalyst containing even doubled amounts of Pd. Furthermore, CA data showed that GNP and Ketjen Black supported catalysts were almost as stable as the commercial Pd/C, although the electrooxidation current at the Vulcan-XC72 based catalysts decreased by ~50% within about 20 min. On the other hand, Vulcan-XC72 supported catalysts showed the highest HCOOH oxidation current and the rest were in close proximity to one another. Finally, morphology and elemental analyses employing scanning electron microscope and energy dispersive X-ray spectroscopy revealed the different catalytic activity on various support materials were concordant with the electrochemical data as the turbostratic substrates contributed better metal dispersion and uniform size distribution.
Financial support from the CAREER Award (CHE-0955878) is gratefully acknowledged.
(Invited) Aromaticity, Cage Structure, and Relative Abundancy of Endohedral Metallofullerenes
Authors: Luis Josep M , Garcia-Borràs Marc , Osuna Sílvia , Solà Miquel 
Published: February 2020

The synthesis of endohedral metallofullerenes (EMFs) from a carbon soot sample of an arc discharge leads to a variety of EMFs that are obtained in different relative abundances. Several different guiding principles as the relative size of the metallic cluster respect to fullerene cage, the number of electrons that are formally transferred from the metallic cluster to the fullerene cage and electrostatic repulsion between charged five-carbon rings have been used to explain the choice of the EMF most stable cages.1 However, no single factor was capable to predict the most stable isomer for all EMFs. Our group has proposed that maximum aromaticity is the driving force that determines the most suitable hosting carbon cage for a given metallic cluster.2 The most stable anionic fullerene isomer is the one whose total aromaticity is maximized. Our results show that maximum aromaticity criterion (MARC) successfully predicts the most suitable C2n cage isomer for the endohedral metallofullerenes with carbon cages from C66 to C104. Furthermore, we have used electronic-based aromaticity measures to show that relative abundances of Sc3N-based EMFs correlate with the aromaticity measures. Our results show that, for the Sc3N-based EMFs, the most abundant EMFs are the most aromatic. This result reinforces the idea that aromaticity plays a key role in determining the stability of EMFs.
1. Garcia-Borras, M.; Osuna, S.; Luis, J. M.; Swart, M.; Sola, M. Chem-ical Society Reviews 2014, 43, 5089.
2. M. GarciaBorràs, S. Osuna, M. Swart, J.M. Luis, and M. Solà, Angew. Chem. Int. Ed. 2013, 52, 9275.

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