bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tuning Electrocatalytic Activity of Ultrathin Pd Shells: CO2 to Fuels
Authors: Fermin David , Humphrey Jo , Celorrio Veronica 
Published: February 2020

It is well established that thin metal layers on a foreign support can exhibit very distinctive electrocatalytic activity with respect to bulk electrodes. In the case of d­-metals, changes in reactivity can be rationalised in terms of the so-called ligand or strain (also known as geometric) effects. Although is commoly argued that ligand effects are rather short range (sub-monolayer to few atomic layers), it is notoriusly difficult to experimentally differentiate the contributions from these two phenomena. In this contribution, we shall explore ligand and strain effects on the electrocatalytic properties of Au-Pd core-shell nanoparticles towards CO2 reduction to fuels. The electrochemical properties and product generation are probed by off-line 1H NMR, differential electrochemical mass spectrometry (DEMS), on-line Mass spectrometry (OLEMS) and in-situ FTIR.
Thin Pd shells were grown onto 20 nm Au nanoparticles employing a colloidal synthesis method at low temperatures, generating continuous shells with tuneable mean thickness between 1.3±0.1 (CS1) and 9.9±1.1 nm (CS10). Selected area electron diffraction patterns revealed that the effective Pd strain decreases from 3.5 to less than 1% in this thickness range, which is consistent with strain relaxtion mechanisms at Au {111} surfaces. DEMS was used to calculate the faradaic efficiency associated with the CO2 reduction vs hydrogen evolution at the core-shell nanostructures supported on a porous carbon layer. The data show that over 90% of the faradaic charge in the range between 0.0 to -0.5 V vs RHE is consumed in CO2 conversion at CS1 nanoparticles, as opposed to approximately 40% in the case of CS10. The analysis of the electrolyte solution employing 1H NMR revealed the formation of HCOO- only in the case of CS10 over a narrow potential range centred at -0.4 V, with faradaic efficiencies close to 30%. Furthermore, CH4 and C2H6 were also detected using OLEMS at potentials as negative as -0.7 V at the CS10 nanoparticles. No products in solution were detected In the case of CS1, indicating that CO is the main product generated over the entire potential range.
The contrast in reaction pathway and electrocatalytic performance are rationalised in terms of the CO affinity to the Pd nanoshells. To probe this, in-situ FTIR studies were performed revealing that the potential dependence of the adsorbed C-O stretching band (stark slope) is significantly weaker on CS1 in comparison to CS10. Furthermore, the effective CO coverage increases with increasing Pd thickness, reaching values reported for polycrystalline bulk Pd electrodes in the case of CS10. These results show that CO has a significantly weaker binding to strain Pd shells (CS1). Finally DFT calculations are used to estimate the contributions of the so-called ligand and strain effects on the local density of states of the Pd d-band. The calculations strongly suggest that the key parameters contributing to the change in mechanism is the effective lattice strain.
Electrochemical Properties and Reactions of Organoboron Compounds
Authors: Suzuki Junji , Tanigawa Masahiro , Kuriyama Yu , Ohtsuka Kazuhiro , Shida Naoki , Inagi Shinsuke , Fuchigami Toshio 
Published: February 2020

Organoboron compounds are highly useful in various fields such as synthetic organic chemistry, pharmaceutical chemistry, and materials chemistry as well as analytical chemistry. However, there have been limited reports dealing with their electrochemical properties and reactions to date.1-3) Quite recently, we found marked negative shifts of the oxidation potentials of alkyl and aryboronic acids and their esters in the presence of fluoride ions compared with those in the absence of fluoride ions. 4-8) It was also clarified that negative shift was derived from the formation of negatively charged boron-ate complex with fluoride ions. In this talk, we focus on our new finding of the β-effect of organoboronic acid esters having a heteroatom or unsaturated bond at their α-position, which is more pronounced compared with that of the corresponding organosilicon compounds. 5,6,8) Anodic radical coupling of organotrifluoroborates7) and substitutions of organoboronic acid esters with oxygen nucleophiles have been achieved. 4-8) Thus, we have shown that boryl groups work as electroauxiliaries like silyl groups.
References:
1) J. Yoshida, T. Nokami, and S. Suga, in Organic Electrochemistry, 5th Ed., O. Hammerich and B. Speiser (Eds.), CRC Press, FL, (2015), Ch. 35
2) H. Scha¨fer and D. Koch, Angew. Chem. Int. Ed.
11, 48 (1972).
3) L. A. Shundrin, V. V. Bardin, H.-J. Frohn, Z. Anorg. Allg. Chem. 630, 1253 (2004).
4) J. Suzuki, N. Shida, S. Inagi, and T. Fuchigami, Electroanalysis, 28, 2797 (2016).
5) M. Tanigawa, Y. Kuriyama, S. Inagi, and T. Fuchigami, Elecrochim. Acta, 199, 314 (2016).
6) K. Ohtsuka, S. Inagi, and T. Fuchigami, ChemElectroChem, in press, DOI:10.1002/celc.201600519.
7) J. Suzuki, M. Tanigawa, S. Inagi, and T. Fuchigami, ChemElectroChem, in press, DOI: 10.1002/celc.201600451.
8) K. Ohtsuka, S. Inagi, and T. Fuchigami, J. Electrochem. Soc. in press, DOI: 10.1149/2.0561702jes.
Direct EPR Evidence of Cathodic ECL Coreactant Intermediates of Benzoyl Peroxide and Ammonium Persulfate
Authors: Bastola Pradip , Miao Wujian 
Published: February 2020

Electrogenerated chemiluminescence (ECL) coreactants are crucial towards their roles in forming radical intermediates for chemical oxidation or reduction of the ECL emitters, such as rubrene (RUB) or 9,10-diphenylanthracene (DPA), to form excited state species that emit light. During the cathodic potential scanning, ECL coreactants such as benzoyl peroxide (BPO) and ammonium persulfate were believed to generate benzyloxy free radical (C6H5CO2
• or BPO•) and sulfate anion radical (SO4
-•), respectively, resulting in the chemical oxidation of the ECL emitter and eventually the ECL production. The direct electron paramagnetic resonance (EPR) evidence of the above radical intermediates, generated via chemical reduction of the ECL coreactant benzoyl peroxide in MeCN and ammonium persulfate in water using hydrazine as the reducing agent and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin trapping agent, was obtained. Additionally, EPR spectra of C6H5CO2
• (without DMPO trapping) generated from solid state using UV irradiation were consistent with the spectra obtained from solution phase. The EPR spectra of SO4
-•(with DMPO trapping) were also obtained. Simulations of the experimentally acquired EPR spectra were conducted with EPR simulating software, such as PEST winsim.
Financial support from the NSF CAREER Award (CHE-0955878) is gratefully acknowledged.
Prospects for Validation of PEM Fuel Cell Models Using Current Distribution
Authors: Beruski Otávio , Perez Joelma 
Published: February 2020

Complex systems have a lot to gain from computational models, as they provide information out of reach of most individual experimental techniques. The possibility of providing full control over variables and parameters of a given system, as well as enabling the comparison of mathematical approaches, are a few of the many advantages of employing a well-developed computational model. Such is the case for fuel cells, notorious for its complex interactions between micro, meso and macro-scale components, and difficulty in obtaining reliable information from its dynamics. However, it is of high importance that the models be continuously improved and validated, not only against the already established empirical data, but also against new techniques that provide furtherinsights in the system. In this context, an ongoing work is being developed to provide robust data from current distribution, a rather unused technique when it comes to PEM fuel cell model validation, in order to further improve model development and provide a complementary dataset for validation. It is seen that, when using a simple 3D model of a 50 cm2 PEM fuel cell, with a well-established mathematical formulation, it is possible to reproduce most of the experimental polarization curve, within one deviation, despite the uncertainties on material properties (upper graph in Figure). On the other hand, the current distribution greatly differs between the experimental and computational results, even qualitatively (lower graph in Figure: applied current 3.0 A, current values normalized by sum over all collection points). In general, the same behavior is observed throughout the polarization curve and for different inlet flow rates. Although the lack of proper characterization of the electrode materials may be partially to blame, the consistent differences in the spatial distribution of the current points to broader issues: i) the polarization curve is rather insensitive to finer properties of the system, being a poor result for validation; and ii) the lack of accuracy of widely used mathematical formulations in describing the spatial dependency of variables of interest, in this case current, even in a relatively small device and conservative conditions. These preliminary results and the observed tendencies add to the growing consensus that greater efforts are needed in order to develop and validate useful fuel cell models. In particular, it is suggested that current distribution results, if available, provide more information and greater constraints for fuel cell development and validation, than when relying solely on polarization curves.

Figure 1
Ion Transport in Single-Ion Conducting Polymer Electrolytes for Lithium Batteries
Authors: Upadhyay Sunil , Schaefer Jennifer L. 
Published: February 2020

Electrochemical energy storage devices are increasingly desired for consumer vehicle electrification and renewable power utilization. Safety and performance of batteries is strongly dictated by the performance of the electrolyte. Polymer electrolytes offer advantages over liquid and inorganic solid-state electrolytes, as they are non-leakable and non-volatile, yet flexible. Single-ion conducting electrolytes that eliminate ion concentration gradients offer further advantages: greater electrochemical stability allowing for higher voltage cells, lower interfacial impedance, and higher theoretical charge/discharge rates. Single-ion conducting polymer electrolytes may simply be created by titration of an ionomer with the active ion – Li+ in a Li-ion battery, for example. Unfortunately, the drastically low ionic conductivity of single-ion conducting polymer electrolytes without added solvent has precluded their commercial application thus far. Improved understanding of lithium ion transport mechanisms is critical for the development of high performance electrolytes. Our efforts in this area are focused on understanding ion states and ion transport in two distinct classes of single-ion conducting polymers. The first class of materials of interest are polyethers with highly dissociable tethered anions, where the research focus is to understand ion-pair dissociation and ion states that contribute to conduction. The second class of materials of interest are ionomers with solely non-polar polymer components, where we aim to understand ion transport through ionic domains.
Tunable-High Performance Sustainion™ Anion Exchange Membranes for Electrochemical Applications
Authors: Sajjad Syed D. , Gao Yan , Liu Zengcai , Yang Hongzhou , Masel Rich 
Published: February 2020

This paper will describe the development and applications of Dioxide Materials’ new brand of novel Sustanion™ polymer Anion Exchange Membranes (AEMs). The styrene backbone of these membranes is functionalized in various degrees by the imidazolium functional group and includes other additives to yield several compositions for tailoring the properties and performance of these membranes. The advantage of using the Sustanion™ membranes over any commercially available AEM technologies is demonstrated in terms of their significantly higher anionic conductivities in Figure 1. Furthermore, the membranes are stable and maintain these conductivities when exposed to 1M KOH at 60 oC for up to a period of at least 1500 hours.
We have corroborated these finding by testing these membranes in-situ CO2 and water electrolyzers. Our results speak for themselves. The CO2 electrolyzers have run under 3V at 200 mA/cm² with a voltage rise of only between 4 and 6 µV/hr for 3700 hours. Keep in mind, these currents are more than a factor of 4 higher than our closest competitor. For water electrolyzers, our Sustainion™ membranes have helped us embark on the Holy Grail of base metal catalysts using NiFe on stainless steel anodes and NiFeCo cathodes. We can maintain 1 A/cm² at 1.9V at 60oC in 1M KOH for 200 hours with less than 5 mV voltage variation. This is unprecedented since under the same conditions, we have failed to find a single instance in literature of values surpassing the above results by including even high loadings of precious metal catalysts. The cell is still running.
As such, we are expecting to offer these membranes for beta-testing by various academic and industry groups. Based on our current findings, we envision the Sustainion™ membranes making similar breakthroughs in applications of alkaline anion exchange based fuel cells, flow batteries and even electrodiyalsis among other untapped electrochemical applications.

Acknowledgement

Parts of this work were supported by ARPA-E under contracts DE-AR0000345 and DE-AR0000684 and by 3M. The opinions here are those of the authors and may not reflect the opinions of ARPA-E or 3M. Assistance from colleagues, collaborators and friends from 3M are gratefully acknowledged.

Figure 1
Pentablock Ionomer Based TEOS-TIP Hybrid Nanocomposites: Morphology, Physical Properties, and Ion Transport
Authors: Huang Fei , Zheng Wenjian , Cornelius Chris 
Published: February 2020

Nowadays, pure materials cannot embody all the physical, chemical, and mechanical properties required for a given application. Therefore, hybrid inorganic-organic composite materials were created to fill this critical void. The hybrid composites depend not only the properties of individual components, but also on the interfacial interactions between inorganic and organic phases. The significance of this work is to control the interaction-structure-property relationships of hybrid inorganic-organic nanocomposites in many applications such as fuel cells, lithium-ion batteries, biomimetic actuator, and water purification.
The PBC based hybrid organic-inorganic films were synthesized based on tetraethylorthosilicate (TEOS), titanium isopropoxide (TIP), and poly(t-butylstyrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene-b-t-butylstyrene) or pentablock copolymer (PBC) via sol-gel chemistry. A ternary phase diagram was estibalished to understand the homogeneity of TEOS-TIP sol-gel system dependent on initial sol composition and reaction conditions leading to controllable materials. All hybrid PBC-TEOS-TIP membranes exhibited higher water uptake than unmodified PBC membranes. Proton conductivity increased 80% from 58 mS/cm for unmodified PBC film to 85 mS/cm for hybrid nanocomposite film due to the role TEOS-TIP within it. This can be attributed to the partial charge transfer from the titanate’s inorganic domains to sulfonate groups that promote acid dissociation and proton attraction. The PBC’s microphase-separated morphology changed from well-ordered lamella-like structure to a random and homogenous distribution of ionic domains with increasing TIP concentration, which was observed from AFM and SAXS results. TGA analyses revealed a decrease in degradation temperature due to titanate's catalytic character, and DMA results demonstrated reduced polymer chain mobility caused by inorganic-organic interactions. Finally, these PBC-TEOS-TIP hybrid composites were used as proton-exchange membranes (PEM) for hygroden fuel cells.
Conductive Polymer for Reversible Overcharge Protection in Lithium-Ion Batteries
Authors: Wang Bin 
Published: February 2020

Great improvement in the safety of lithium ion battery is needed to meet the full requirements of electric vehicles(EV). Among these safety hazards, overcharge has long been recognized as a primary concern because it can lead to dangerous events such as thermal runaway,fire and explosion. The electroactive polymer approach utilizes the unique electronic properties of the polymers to form a reversible resistive shunt between the current collectors and protect the cell from overcharging. The process is self-activated by voltage, and it does not pose interference during normal cell charge and discharge.
In this work, we report the recent progress in cell overcharge protection for high-energy-density lithium ion batteries. By incorporating the reversible electroactive polymers into highly porous membrane separators, we demonstrate that the composites can provide reversible and stable overcharge protection for a variety of cell chemistries. The results for the protection of Li1.05Mn1.95O4 or LiNi0.8Co0.15Al0.05O2 electrode will be discussed. Both cells were protected at a steady state voltage of 4.5 V for well over 100 cycles.
Characterizing the Ionic Transport through Nanoporus AAO Membranes: Effect of Surface Charge Due to Biomolecule Functionalization
Authors: Gosai Agnivo , Shrotriya Pranav 
Published: February 2020

Nanoporous anodic aluminum oxide (NAAO) membranes have been utilized as sensing platforms for a variety of chemical/biological targets in recent years. NAAO membrane based sensors are attractive due to the low cost, simple instrumentation and fast response time. Traditionally, biomolecule functionalized NAAO membranes have been used as working electrodes in electrochemical sensors. Afterwards due to binding with the target molecule, the electrical characteristic of the working electrode (for e.g. impedance) is changed which is calibrated with different concentrations of the target species.
Previous research has primarily focused on recognition of target molecule by characterizing the impedance change of the working electrode. In the present work, we have conducted experiments to understand how the ionic transport (of the electrolyte) across the NAAO membrane is affected due to the functionalization of biomolecules. We have used electrochemical impedance spectroscopy (EIS) to analyze the effect of different biomolecules on the membranes.
As a test example, we have chosen the thrombin binding aptamer as the sensing molecule and human alpha thrombin as the target molecule in the experiments. The NAAO membranes were sputter coated with gold and the effect of sputtering on the pore size was analyzed through scanning electron microscope (SEM). Afterwards the membrane was functionalized with thiolated thrombin binding aptamer (TBA). Then the membrane was placed in a custom made electrochemical cell and a four-electrode system was utilized to measure the impedance change across the membrane. The electrolyte was maintained at a physiological pH value. When the system was treated with thrombin protein, upon binding with the TBA, it produced a change in the impedance, which was characterized by EIS. We have repeated the experiments for different pore diameters, different sputtering time and concentrations of thrombin. A negative control experiment was also carried out to check the effect of other proteins on the system.
Finally, we have modeled the system using a modified Randles circuit to look at the contribution of protein-aptamer binding on the following parameters: resistance due to the pores, capacitance of the membrane and the electrolytic resistance. We have found that there is a positive correlation between these parameters and successful binding of the biomolecules which in turn can be utilized to calibrate the ionic transport across the membrane as well as utilize the system as a sensor for target proteins.
Simultaneous Optical and Electrochemical Imaging of Shewanella Oneidensis
Authors: Calhoun Margaret C , Crisostomo David , Cliffel David E 
Published: February 2020

Shewanella oneidensis is an electroactive bacterium that has the ability to harvest electrons from insoluble metals in its environment for biological processes via dissimilatory metal reduction (DMR). There are 4 mechanisms by which S. oneidensis accomplishes these reductions: direct contact of the outer cell membrane to the metals, protein “nanowires” that extend from the cell surface, metal chelators that solubilize the metals, and small molecule electron shuttles. While evidence suggests S. oneidensis predominately utilizes soluble electron shuttles for DMR, it has yet to be directly proven. If the exact mechanism or mechanisms could be elucidated, S. oneidensis could be employed in a fuel cell that rids polluted water of metal contaminants in the process of generating electricity.
For this research, scanning electrochemical microscopy (SECM) was used to investigate the DMR processes of S. oneidensis. By coupling SECM to an inverted microscope, we optically imaged the bacteria during two-dimensional electrochemical measurements. Combined with advances in carbon ultra-micro electrode fabrication, this optical-SECM was used for high resolution scans of S. oneidensis biofilms, as well as planktonic bacteria.
Sol-Gel Synthesis and Photoluminescent Investigation of SrZnV2O7:Eu3+ Nanophosphors
Authors: Khatkar Satyender Pal 
Published: February 2020

Sol-gel Synthesis and Photoluminescent Investigation of SrZnV2O7:Eu3+ Nanophosphors

S.P. Khatkar1*, V.B. Taxak1, Mandeep Dalal1

1Department of Chemistry, Maharshi Dayanand University, Rohtak -124001, India
*Corresponding Author: Tel: +919813805666

E-mail: s_khatkar@rediffmail.com
Recently, opto-electronic study of rare earth doped inorganic host materials emerged out as one of the most proficient field in nanotechnology. White LEDs exhibit excellent advantages such as more economical power consumption, longer life, being mercury-free and less pollution as compared to the conventional halogen and incandescent lamp. However, white LEDs using GaN based chip system have poor color rendering index and low chromatic stability under different driving currents. Therefore, near UV-LEDs coated with RGB phosphor offer effective and attractive solution for the problem of white light emission with lower color temperature. In present work, europium doped SrZnV2O7 nanophosphor was successfully synthesized via sol-gel approach in nano range with particle size in 70-90 nm range confirmed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The crystallinity of pure phased nanophosphor in monoclinic lattice with the P121/n1 (14) space group was confirmed through X-ray diffraction analysis. The nanophosphor yields strong red emission at 616 nm attributed to 5D0→ 7F2 transition of Eu3+ ion when excited at 395 nm with optimum concentration for maximum luminescence was 4 mol%. The photoluminescent excitation and emission spectra of synthesized samples suggest their potential application in phosphor converted white LEDs with NUV excitation.