bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Impacts of Anions on Oxygen Reduction Reaction Kinetics on Platinum and Palladium Surfaces
Authors: Shao Minhua , Zhu Shangqian
Published: February 2020

Fundamental understandings on the impacts induced by anions and cations on oxygen reduction reaction (ORR) are of great interest in designing more efficient catalysts and identifying reasons for discrepancies in activities measured in different protocols. In this study, the specific adsorption of F-, Cl-, ClO4
-, CO3
2-, SO4
2-, Nafion ionomer, and citrate anions on Pt/C, Pd/C and transition metal, N co-doped carbon-based (Me-N-C) catalysts, and their effects on the ORR kinetics were systematically investigated. It was found that ClO4
- had a negligible impact on the ORR activity of Pt/C possibly due to its weak adsorption. Nafion ionomers, on the other hand showed a significant poisoning effect on the bulk Pt electrode. Its impact on Pt/C, however is negligible even with a very high I/C ratio (1.33) in acidic solutions. The three catalysts showed different behaviors in alkaline solutions. The non-covalent interaction between hydrated cations and surface OH groups was found on Pt/C and had an obvious impact on the ORR kinetics. This non-covalent interaction, however was not observed on Pd/C, which showed the same ORR activity in all three electrolytes (LiOH, NaOH and KOH). The ORR activity of Me-N-C increased following the order of KOH < NaOH < LiOH. This trend is totally opposite to that of Pt/C. Self-dissociation of citrate anion was found to occur on both Pt/C and Pd/C in the H adsorption/desorption and double layer regions. For the first time, surface enhanced infrared absorption spectroscopy (SEIRAS) with the attenuated total reflection (ATR) technique was used to investigate the self-dissociation of citrate on Pt and Pd thin film electrodes. The break of carboxylic groups and carbon backbone were proposed as possible dissociation pathways for citrate. The adsorbed species have a negligible effect on ORR activity on Pt/C as they are removed by oxidation before 0.75 V. In contrast, their oxidation on Pd/C surfaces is not completed until 0.91 V, which causes a lower ORR activity observed in rotating disk electrode measurements.
Hybrid Carbon Nanostructures As Efficient Electrocatalysts
Authors: Ozden Sehmus , Martinez Ulises , Mohite Aditya D.
Published: February 2020

One of the excellent clean-energy source is hydrogen that can be produced from solar-driven water-splitting devices. Developing novel suitable catalyst that can efficiently catalyze significant electrochemical processes such as hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is one of the biggest challenges in developing new energy conversion technologies for water-splitting devices. In addition of water-splitting catalyst, oxygen reduction reactions (ORR) is another important electrochemical reaction that needs novel efficient electrocatalyst for clean energy. Therefore, the development of inexpensive and efficient devices will not only address the energy sustainability, but also, address the climate-change challenges. There are several key issues related to the existing electrocatalysts such as their high-cost and low electrochemical stability, which is limiting their large-scale applications in relevant clean energy technologies. Therefore, the development of novel electrocatalysts with high catalytic activity, long durability and low-cost will significantly facilitate the awareness of sustainable energy. Here, we will discuss the development of highly-porous, hybrid structures of low-dimensional hybrid nanomaterials as efficient electrocatalysts including theoretical calculations that discloses the enhanced electrocatalytic properties of these hybrid structures creating intrinsic chemical and electronic coupling.
Transition-Metal Oxide Electrocatalysts with Well-Defined Surface and Sub-Surface Layers
Authors: Kuo Ding-Yuan , Paik Hanjong , Schlom Darrell G. , Suntivich Jin
Published: February 2020

The concept of a platinum-monolayer electrocatalyst, a heterostructure with a platinum-monolayer shell surrounding a sub-surface transition-metal core chosen to strain or electronically modify the overlayer shell to maximize the electrocatalytic activity, has profoundly influenced the design of the oxygen-reduction electrocatalysts in the past decades. We present a strategy to translate this concept to non-platinum electrocatalysts by using advanced deposition technologies enabled to control the surface and sub-surface chemistries in transition-metal oxides. Starting from RuO2(110) films epitaxially grown on TiO2(110) substrates, we manipulate the surface chemistry by controllably deposit Ru1-xTixO2 overlayers on RuO2, effectively creating a Ru1-xTixO2/RuO2(110) heterostructure. The high quality of the oxide films grown using molecular-beam epitaxy affords the ability to extract the oxygen electro-adsorption energetics, consequently allowing us to quantify the influence of the surface and sub-surface layers on the electro-adsorption and electrocatalytic activity. Putting together the adsorption energetics allows us to test the mechanism for the oxygen evolution reaction (OER) on RuO2(110) and Ru1-xTixO2/RuO2(110) electrocatalysts. We will discuss the implications of these insights in the context of how to find a combination of surface and sub-surface layering to design and create new OER electrocatalysts.
Electrocatalytic Property of Pt Atomic Layers on Pd Nanocrystals for Ethanol Oxidation
Authors: Lin Yan-Fen , Tian Na , Sun Shi-Gang
Published: February 2020

Platinum is actually the irreplaceable catalyst for proton-exchange-membrane fuel cells (PEMFCs) and direct-alcohol fuel cells (DAFCs). Due to the high price and rare reserve, further improving the activity while decreasing the loading of Pt catalyst in membrane-electrolyte-assembly (MEA) of fuel cells is crucial. Single atomic Pt layer even single Pt atom catalysts are the most promising and challenging strategy. In this study, catalysts of Pt atomic layers from sub-monolayer to multilayers on Pd tetrahexahedral nanocrystals (THH Pd@Ptn NCs) with high-index faceted and {111}-faceted Pd NCs were prepared through Pt galvanic displacement of UPD Cu. The results demonstrate that the catalytic activity for ethanol electrooxidation is very low on Pt monolayer (THH Pd@Pt1 NCs), while the highest activity is measured on Pt 2-layers (THH Pd@Pt2 NCs) amongst the THH Pd@Ptn NCs (n<1, =1-5) studied. The catalytic activity of THH Pd@Pt2 NCs is even higher than that of pure THH Pt NCs. Through in-situ CO-probe FTIR spectroscopic study, it has revealed that both the interaction of Pt layer with Pd nanoparticle (the strain and ligand effects) and the structure of surface atom arrangement play important roles in manipulating the activity of Pt catalyst. The study has thrown insight into design and preparation of high-active and ultra-low loading Pt catalysts for fuel cell applications.

Acknowledgement: This work was supported by Natural Science Foundation of China (21573183, 21621091).

References:

Li, P. Liu and R. R. Adzic, J. Phys. Chem. Lett., 2012, 3, 3480-3485.

Liu, D. Gokcen, U. Bertocci and T. P. Moffat, Science, 2012, 338, 1327-1330.

Yang, J. Kim, Y.J. Tak, A. Soon, H. Lee, Angew. Chem. Int. Ed. 2016, 55, 2058.
(Invited) Advancements in Ethanol Oxidation Reaction Mechanisms with Alkaline Direct Ethanol Fuel Cells
Authors: Chen Rongrong , Guo Junsong
Published: February 2020

Since the development of alkaline anion exchange membranes (AAEMs), Direct Ethanol Fuel Cell (DEFC) has gained significant research interest as an alternative to high-cost Direct Methanol Fuel Cell (DMFC) based on proton exchange membranes (PEMs). There are several advantages to utilization of ethanol fuel compared to methanol fuel, including: 1) existing infrastructures for ethanol production from various biomasses, liquid fuel storage, and transportation, 2) high specific energy density, and 3) decreased chemical toxicity. Furthermore, alkaline DEFCs have several advantages over PEM DMFCs, including: 1) improved kinetics of anodic ethanol oxidation reactions (EOR) and cathodic oxygen reduction reactions (ORR) in alkaline media; and 2) a wide range of catalyst materials in addition to Pt are stable in alkaline media and can be chosen as the catalysts for either EOR or ORR. Consequently, ADEFCs that do not require expensive Pt catalysts become feasible.

However, the poor kinetics of ethanol oxidation reaction (EOR) and the need to break C-C bonds to complete oxidation of ethanol to CO2 have been major challenges for the development of DEFCs. Precious metals such as Pt and Pd are commonly used as primary catalysts for EOR in ADEFCs. In order to increase catalyst performance, Pt and Pd are usually combined with other transition metals, such as Ru, Sn, Pb, Au, Ni, Ag, Cu or Bi, as alloys, deposits, or ad-atoms. In our previous work, the electrocatalytic activity of PdxRuy/C catalysts for the EOR was demonstrated to be much better than that of Pd/C in ADEFCs. The transition metal Ru in RuxPdy was thought to enhance ethanol oxidation with the assistance of hydroxyl groups on the catalyst surface formed at lower potentials. However the oxidation of ethanol in alkaline media is very complex and involves many types of intermediates, such as C1 species (most likely COad and CHx,ad), OHad, CH3COad and other forms of acetaldehyde in alkaline media. The roles of Ru in PdxRuy/C and durability of PdRu/C catalysts for ethanol oxidation have not been elucidated and require further investigation.

In our recent work, we conducted comprehensive studies of EOR on several Pt-based and Pd-based catalysts by not only using half-cell testing, such as cyclic voltammetry (CV) and chronoamperometry (CA), but also fuel cell testing under various test conditions. An accelerated test was established to evaluate the stability of anode catalysts. In situ FTIR experiments were carried out to determine EOR intermediate and final products on these various catalyst systems. These comprehensive studies provide novel insights regarding the roles of second transition metal (Ru, Pb or Cu) in Pd or Pt catalyst for EOR in alkaline media, unveil the causes of the performance degradation of fuel cells with traditional catalysts, and indicate that catalysts with good initial performances are not essential for being appropriate for ADEFC applications.
Synthesis of Nanostructured Bimetallic Catalysts for Electrochemical Applications
Authors: Chen Jingyi
Published: February 2020

Bimetallic nanostructures of specific compositions and enclosed by certain facets can significantly alter their physical and chemical properties and thus provide the opportunities to tailor them for particular electrochemical applications. Despite significant progress in recent years, it is still a grand challenge to control the spatial distribution of elements and surface structure of bimetallic nanoparticles. Thus, it remains very difficult to understand the properties of bimetallic nanoparticles, and even more challenging to overcome the formidable barriers to the rational design of bimetallic nanoparticles with the desired performance. This research focuses on the development of seed-mediated synthesis in solution aiming to precisely control the atomic arrangement in the bimetallic catalysts to establish the structure-composition-property relationship for electrocatalytic applications. In seed-mediated synthesis, the seeds can be preformed or in situ formed as a primary nanoscale substrate, followed by reducing secondary precursors to form bimetallic or multimetallic nanocatalysts. By controlling the shape of the seeds and reduction kinetics, well-defined bimetallic and multimetallic nanostructures can be obtained. In this work, CuPt and CuPtRu nanomaterials will be used as an example to demonstrate how changes of spatial atomic arrangement in the nanostructures influence their electrocatalytic properties for methanol oxidation. Fine tuning and mechanistic study of these synthetic strategies provide us fundamental understanding for precise control of bimetallic nanostructures to tackle problems in materials chemistry and open up the possibility for rational design and synthesis of future complex nanoarchitectures towards electrochemical applications.
Electrooxidation of Propylene to Acrolein
Authors: Seger Brian , Winiwarter Anna , Stephens Ifan , Chorkendorff Ib
Published: February 2020

Short chain alkanes and alkenes (C1-4) typically have little economic value and are difficult to transport since they are gases. Because of this, these hydrocarbons are of so low value that they are often flared during extraction of oil.1 This talk investigates electrochemically partially oxidizing these materials to high-value liquid products, thus increasing both the value and ease in transportation. If the oxidation is cathodic enough (< ~ +0.9 V vs. RHE) this can be combined with a standard oxygen reduction reaction cathode in a PEM fuel cell type approach to produce a device that does not consume electrical power, but actually has the potential to produce a small amount of power.2

Specifically this talk focuses on partial electrochemical oxidation of propylene to a variety of high value products such as acrolein, propylene oxide, propylene glycol, and acrylic acid and low value products such as CO2, and acetic acid. Using a Pd catalyst, we analyse the effects of pre-treatment, potential, pH and other factors in optimizing high value products while minimizing low value products. As shown below, one of the most promising findings is a high degree of acrolein selectivity at 0.9 V vs RHE in acidic solutions.

The figure below shows that we can achieve stable electrochemical oxidation of propylene for 1 hour and produce acrolein with a selectivity of near 80%.

Elvidge, C. D.; Ziskin, D.; Baugh, K. E.; Tuttle, B. T.; Ghosh, T.; Pack, D. W.; Erwin, E. H.; Zhizhin, M., A Fifteen Year Record of Global Natural Gas Flaring Derived from Satellite Data. Energies 2009, 2 (3), 595-622.

Yamanaka, I., Active control of catalysis and product selectivity by a fuel cell system. Research on Chemical Intermediates 2006, 32 (3-4), 373-38

Figure 1
Enhancement of Electrochemical Performance of Bilirubin Oxidase Modified Gas Diffusion Biocathode By Porphyrin Precursor
Authors: Arugula Mary , Pinchon Erica , Pant Kapil , Singhal Sameer
Published: February 2020

Recent studies have focused on tailoring the catalytic currents of multicopper oxidase (MCO) enzymes-based biocathodes to enhance oxygen reduction. Biocathodes modified with natural substrates specific for MCO enzymes demonstrated drastic improvement for oxygen reduction. Performance of 1- pyrenebutanoic acid, succinimidyl ester (PBSE) and 2,5- dimethyl-1-phenyl-1H-pyrrole-3-carbaldehyde (Di-Carb) oriented bilirubin oxidase (BOx) modified gas diffusion biocathode has been drastically improved by incorporating, a porphyrin precursor as electron transfer moiety. Porphyrin precursor modified electrodes demonstrated direct electron transfer reaction of BOx exhibiting larger O2 reduction current density in phosphate buffer solution (pH 7.0) without the need of a mediator. A remarkable improvement in the catalytic currents with 2.5 fold increase was achieved compared to non-modified oriented BOx electrodes. Moreover, a mediator-less and compartment-less Glucose/O2 biofuel cell based on direct electron transfer (DET) type bioelectrocatalysis via the BOx-cathode and the glucose dehydrogenase (GDH)-anode demonstrated peak power densities of 1mW/cm2 at pH 7.0 with 100mM glucose/10mM NAD fuel. The maximum current density of 1.6mA/cm2 and the maximum power density of 0.4mW/cm2 were achieved at 300mV with non modified BOx cathode, while 3.5mA/cm2 and 1.1mW/cm2 of current and power density was achieved with porphyrin precursor modified cathode. The performance improved 2.4 times which attributes to the porphyrin precursor acting as a natural substrate and activator for BOx activity enhancement.
In Situ Development of Efficient Electrogenic Bacterial Community in Urine Fed Microbial Fuel Cell Cascades
Authors: Obata Oluwatosin , Walter Xavier Alexis , Greenman John , Ieropoulos Ioannis
Published: February 2020

Microbial fuel cell technology harnesses the potential of some naturally occurring bacteria for electricity generation. To initiate the operation of microbial fuel cells, inoculation with different types of bacterial community, including those found in activated sludge, are employed. There are however, health hazards associated with the use of digested activated sludge and this of course depends on where the sample has been sourced from. Organisms such as Mycobacterium tuberculosis, Pseudomonas aeruginosa and enteric viruses have been reported in activated sludge, which can have practical difficulties when working with such samples. Therefore, the development of an efficient electroactive bacterial community, capable of producing optimum power output without the need for sludge inoculation, would eliminate any potential risks. In the current study, we developed an efficient electroactive bacterial community within a ceramic based MFC system, using only fresh urine as the inoculum. Efficient biofilm development was achieved by stepwise adjustment of the external resistance, following 48 hours of open circuit operation. This resulted in a uniform bacterial community with power output levels >50% higher than those inoculated (as per standard practice) with activated sludge. The results showed that power generation begins within 2 days of experimental set-up, compared to at least 5 days in sludge inoculated systems, thus significantly reducing start up time. Incidentally, the development of the bacterial community occurs irrespective of the freshness or age of the urine feed. Given the difficulty in moving suitable activated sludge across countries/borders and that practical application of MFCs technology is more likely to occur in remote rural locations, it is possible that suitable activated sludge might not be available for inoculation locally. Therefore, deployment of MFC systems capable of producing optimum power without the need for sludge-inoculation would be beneficial to their widespread global application. This is the first report of an in situ development of an electroactive bacterial community in urine-fed MFC systems that outperform those initially inoculated with activated sludge.

Keywords:
In situ bacterial community development, Microbial fuel cell, Fresh urine, Electrogenic bacterial community.
Design and Characterization of a Conductive Cellulose Nanocomposite Anode for Enhancement of Microbial Fuel Cell Efficiency
Authors: Keleher Jason J. , Beckmann Thomas J. , Lambert Joseph Edward , Lanasky Katelyn Patricia , Yuede Nicole Elizabeth
Published: February 2020

Microbial fuel cells (MFCs) have gained a significant amount of interest in the pursuit of alternative energy sources. Current research has investigated the optimization of maximum power production via the development of novel carbon-based electrodes to reduce cost and increase efficiency. This research focused on the development of a biomimetic cellulose-based electrode containing a nanocomposite conductive polymer matrix which has shown to improve biofilm stability and electron transfer. More specifically the incorporation of β-cyclodextrin (β-CD) enhances microbial adsorption and biofilm formation via increased docking efficiency. Furthermore, the addition of a conducting polymer has enhanced electron transfer throughout the composite medium. Atomic force microscopy (AFM) and open circuit potential (OCP) measurements were correlated to microbial fuel cell performance to further validate the role of biofilm formation and the electron transfer process. Additionally, the mechanisms of individual cellular adhesion and its role in electron transfer were probed using epifluorescent optical tweezers coupled with OCP measurement.
(Invited) Computational Insights to the Charge Transfer Reaction at the Complex Li/SEI/Electrolyte Interface
Authors: Qi Yue , Li Yunsong
Published: February 2020

The performance of Li-ion batteries (LIB) is highly dependent on the electrochemical reactions occurring at the Solid Electrolyte Interphase (SEI). However, its nanometric scale thickness combined with its complex structure makes the SEI remains “the most important but the least understood in LIB”. Simulations can provide critical insights to the electrochemical reactions at the electrode/SEI/electrolyte interface. Density Function Theory (DFT) and Density Functional Tight Binding (DFTB) methods were used to model the charge transfer reaction at a Li/Li2CO3/liquid Ethylene carbonate (EC) electrolyte interface. In this study, we first developed a new set of DFTB parameters for Li-X (X=Li, H, C, O) interactions by fitting and calibrating with various DFT calculations. Then, the lithiation and delithiaiotn processes were simulated.

The simulation clearly showed four layers Li2CO3 can effectively protect the Li electrode surface within the simulation time. During de-lithiation, it was energetically favorable to form a void at the Li/Li2CO3 interface. The lithiation process was simulated as three steps: Li+ desolvation at the SEI/Electrolyte interface, Li+ diffusion through the Li2CO3 layer, and annihilation of e- and Li+ at the Li surface. The simulation clearly demonstrated the charge transfer reaction of Li+ + e- -> Li0 occurs at the Li/Li2CO3 interface or beneath the SEI layer. The energy profile of this reaction was simulated under different applied voltage. It was found that the experimentally defined zero voltage of Li+/Li0 corresponds to a negatively charged Li metal surface at a charge density of ~ 1e/nm2. When the electron density is larger than this (more negative potential), Li plating occurs; while when the electron density is lower than this (more positive potential), Li stripping occurs. The excess electrons on the Li surface will trigger more electrolyte decomposition and Li-dendrite formation when SEI fractures.
(Invited) Tailored ORR Electrocatalysts
Authors: Becknell Nigel , Lopes Pietro Papa , Lv Haifeng , Coleman Eric , Li Dongguo , Wang Rongyue , Strmcnik Dusan , Markovic Nenad M , Stamenkovic Vojislav
Published: February 2020

The progress in the ORR electrocatalysis over the last two decades has been achieved primarily through the fundamental understanding of processes that are taking place at well-defined surfaces. True nature of active sites is an important topic in the literature, however, despite decades of persistent studies aimed to reveal the fundamentals, insight at atomic level is still lacking. Properties such as surface crystallographic orientation, morphology, composition and defects are yet to be assigned to the correlation between the atomic structure and catalyst activity. For the first time, we report on the atomic structure that has been investigated in combination with durability. The ultimate precision that goes beyond a part per million of a single atomic layer has been achieved in determining electrocatalytic properties of the ORR catalysts. Obtained knowledge is of paramount importance in design of advanced highly functional nanoscale materials. Single crystalline and thin film based surfaces of Pt-alloys have been characterized by AES, LEED and UPS, which was followed by controlled transfer to electrochemical, in-situ FTIR and STM cells. These findings have been further used to optimize a unique RDE coupled ICP-MS system. Such effort has led towards the design and synthesis of real-world materials with superior properties that will be reported here.
Rational Design of Metal-Organic Frameworks/Gels As Efficient Catalysts for Oxygen Reduction Reaction
Authors: Wang Hao
Published: February 2020

The growing pollution and energy crisis emphasize the need for the development of clean energy, such as fuel cells and metal-air batteries, in order to reduce the dependence on fossil fuels. In such clean energy devices, oxygen reduction reaction (ORR) is a key process in determining practical performance. Unfortunately it suffers from sluggish kinetics, resulting in large overpotentials and high efficiency penalties. To address this issue, rational design of non-precious metal catalysts with ORR performance comparable or even superior to precious metal is much needed.

Metal-organic frameworks (MOFs) are porous crystalline materials assembled from metal nodes and organic linkers. MOFs possess high surface areas, open metal sites, and tunable pore structures, and are therefore promising for ORR electrocatalysis, in pristine phases or as self-sacrificial templates (Fig. 1A). Besides MOFs, another class of metal-organic coordinated materials that are of great interest are metal-organic gels (MOGs). MOGs are viscoelastic solid-like materials assembled by metal-organic coordination in conjunction with other interactions. MOGs possess great inclusion properties, design flexibility and ease in synthesis, highlighting themselves as precursors for producing ORR electrocatalysts (Fig. 1A).

Herein, a series of MOFs/MOGs has been synthesized for ORR electrocatalysis. The catalytic ORR performance of the catalysts was evaluated through a rotating disk electrode technique, and the corresponding voltammograms are summarized in Fig. 1B. Several catalysts exhibit ORR activity comparable or greater than that of a commercial Pt/C benchmark, suggesting rational design approach of MOFs/MOGs offers a general solution for production of highly effective non-precious ORR electrocatalysts.

Figure 1
Catalytic Activity of Transition Metal Nitrides for Oxygen Reduction Reaction
Authors: Abroshan Hadi , Bothra Pallavi , Kulkarni Ambarish , Nørskov Jens , Siahrostami Samira
Published: February 2020

The oxygen reduction reaction (ORR) plays a crucial role in the development of cutting-edge technology for clean energy conversion as alternatives to conventional fossil fuel technology. Owing to high cost and scarce supply of current state-of-the-art Pt- and Ir-based catalysts, transition metal nitrides (TMNs) have attracted considerable attention in recent years as a new promising class of electrocatalysts for efficient ORR. Despite the extensive experimental reports, a lack of in-depth understanding of the intrinsic electrocatalytic activity of TMNs poses a serious challenge for systematic development of TMNs based catalysts. Here, we employ density functional theory (DFT) calculations to shed light on the long puzzling area of catalytic activity of TMNs in oxygen reduction reaction. This work demonstrates structure–activity relationships of the nitrides under electrochemical conditions, and offers guidelines on surface modification of TMNs for preparation of efficient catalysts for future generation of energy devices.
Optimising Catalyst Design for Hydrogen Fuel Cells through Structure to Performance Correlations
Authors: Gates Byron D. , Paul Michael T.Y. , Eastcott Jennie , Taylor Audrey K.
Published: February 2020

Electrocatalytic reactions are of particular importance for their application to energy conversion technologies, including energy storage, fuel generation, and consumption of these sources of energy. The efficiency of these processes relies on the balance of many factors including the transport of reagents and by-products at rates applicable for energy demands of the sought-after applications, while also creating a material design that is both economic to prepare and operate. A goal of our research is to seek correlations between the structure of electrocatalysts and their performance. This presentation will discuss a couple of strategies to prepare and evaluate electrocatalysts for hydrogen fuel cells. These strategies include the use of pore forming materials that we utilize for both adjusting the loading, dimensions, and composition of nanocatalylsts, but also enable fine tuning of the ability of these materials to manage transport of gases and fluids. The latter are tuned through adjusting the pore size, connectivity between the pores, and thickness of the desired materials. Tuning these and similar properties of the electrocatalysts and their support materials lends itself to a systematic approach to identifying optimal parameters desired within the catalyst materials, and to guiding the future work in preparing materials on a large scale for incorporation into fuel cell stacks. To evaluate the performance of these electrocatalysts, these materials are incorporated into the cathode catalyst layers of proton exchange membrane fuel cells using a combination of techniques. The techniques include methods that are scalable to larger scales and that are compatible with current manufacturing practices. These catalysts are compared to catalyst films prepared from industry standards for their physical, electrochemical and fuel cell performance characteristics. Some of these methods demonstrate an improved mass activity of the electrocatalyst under fuel cell operating conditions, while others are guiding the design and optimization of future electrocatalysts. These techniques demonstrate a series of approaches to preparing electrocatalysts by design, and to tuning their properties with implications in improving the performance of electrocatalysts for use in hydrogen and possibly other types of fuel cells.
Hidden Features: Characterizing Carbon Electrodes in Low Ionic Strength Electrolytes for Capacitive Desalination Applications
Authors: Hawks Steven A , Fisher Adam , Knipe Jennifer M , Campbell Patrick G. , Stadermann Michael
Published: February 2020

Capacitive desalination (CDI) is a promising technology for reducing the salinity of brackish water streams. CDI typically employs a nanoporous carbon supercapacitor architecture with the added ability to flow electrolyte through the cell for deionization. Unlike supercapacitors, though, CDI operates with low ionic-strength liquids (e.g., 20 mM NaCl). Characterization in these electrolytes unveils important features in the CV and EIS data that are not commonly observed in supercapacitor studies. Examples of such features are the emergence of a strong “charge-transfer” resistance at mid-to-high frequencies in the EIS spectrum, local minima in the CV curves that are related to a point of zero charge, and potential artifacts due to ion depletion. These features ultimately underlie the system capacitance, device resistance, and effective operational voltage window, which are all strongly related to desalination performance. Here we examine these features in flow-through electrode CDI devices (fteCDI) with activated hierarchical carbon aerogel monoliths (HCAMs) derived from carbonized and activated resorcinol-formaldehyde aerogel.

Work at LLNL was performed under the auspices of the US DOE by LLNL under Contract DE-AC52-07NA27344.
A Versatile Redox Responsive Nanoferrogels Based Sensor for Metabolics Analytics
Authors: Mugo Samuel , Lu Weihao , Funk Nicole
Published: February 2020

Developed is an inexpensive label free redox responsive nanoferrogel molecular receptor integrated in a chemoresisistive sensor for rapid detection of Reactive Oxygen Species (ROS) such as H2O2 and H2O2 deriving metabolites, species are of interest in myriad applications including clinical, environmental, food, and plant physiology.

Inexpensively fashioned by contact printing of redox responsive poly(N-isopropylacrylamide hydrogels herewith called ‘nanoferrogel’ on a conductive nanocellulose paper aerogel, the sensor is designed for specimen surface attachment as wearables, non-invasive transdermal sensors, and can be configured as microneedle sensor for in vivo analysis. Operating via ROS oxidation of the nanoferrogel trapped in the conductive aerogel film, the oxidized nanoferrogel volume change results in an overall change in conductivity, linearly proportional to ROS/ROS deriving metabolite concentration.

In the presentation, the responsivity of the nanoferrogel to different ROS species such as H2O2, oxylipin, antioxidants will be demonstrated. The nanoferrogel based H2O2 sensor figures of merit, featuring, rapid (≤ 1min) H2O2 response, high selectivity, low limits of detection (≤ 0.01 µM),and broad linear dynamic range of (≤ 0.03 µM to ≥ 1.5M) will be highlighted. The nanoferrogel is perfectly recyclable, by electrochemical regeneration, affording ≥ 15 multiple usable cycles.

Also showcased will be the adaptability of nanoferrogel for different sensor design configurations (e.g. micro/nanoelectrode systems), with some preliminary data attesting to the sensors utility for fundamental studies and detection of efflux of endogenous and exogenous H2O2 in single cells and other redox biomolecules, (e.g. glucose, choline).

Preliminarily the sensor can be used for detection of bacterial (model used in our study Escherichia coli) autoinducers and metabolites, of importance in bacterial communication-quorum sensing. This would be a useful platform for understanding bacterial biofilm formation. Further, the nanoferrogel sensor fashioned for utility as a wearable device for detection of redox potential and inherent sweat metabolites will be demonstrated.
Competitive Sensing Mode for Electrochemical Detection of Proteins
Authors: Gosai Agnivo , Shrotriya Pranav
Published: February 2020

Electrochemical impedance based biosensors show promise for point-of-care and other applications due to low cost, ease of miniaturization, and label-free operation. Unlabeled DNA and protein targets can be detected by monitoring changes in the impedance of the sensing surface, when a target molecule binds to an immobilized probe. The sensor response is proportional to the number of target molecules bound to the receptor modified surface. In complex matrices such as biological fluids, the sensor response is proportional to both the specific binding of analyte molecules to the receptors (desired signal) as well as non-specific binding of interfering molecules (noise) on the surface. Consequently, reliable detection of the analyte in complex matrices is limited by two parameters: 1) the specific binding affinity between the analyte and receptor molecules; and 2) the sensor sensitivity for analyte-receptor complexes over nonspecifically binding molecules.

We report a novel sensing approach for target detection in solution that can overcome the limitations in specificity due to a lack of sensitive discrimination between specific binding of target analyte and non-specific binding of interfering molecules. The sensing strategy involves functionalizing an array of sensing surfaces with receptor molecules with a reversible bond such that receptor molecules can be released from the surfaces on exposure to the target in solution. Thrombin and its specifically binding aptamer are used as ligand/receptor pair in the sensing experiments. Thrombin aptamers were first immobilized on the sensing surface using a reversible bond and the functionalized surface is exposed to free alpha thrombin in solution. Electrochemical impedance spectroscopy (EIS) is used to monitor the changes in aptamer surface coverage and thus determine the rate of receptor release in presence of thrombin molecules. As a negative control, functionalized surface were also exposed to gamma thrombin as it is structurally similar to alpha thrombin. Experimental results indicate that aptamer release rate is strongly dependent on specifically binding thrombin concentration while it is independent of the non-specifically binding gamma thrombin. In comparison to conventional sensing approaches, this competition sensing shows improvement in dynamic range followed by better sensitivity and specificity.
Palladium Deposited on Multi-Walled Carbon Nanotubes Composite Modified Glass Carbon Electrode As Electrochemical Acetaminophen Sensing Platform
Authors: Wu Yuting , Lei Wu , Hao Qingli , Li Caiwei
Published: February 2020

A novel acetaminophen (AP) sensing upon modification with palladium/multi-walled carbon nanotubes composite (Pd/MWCNTs) has successfully developed. The Pd nano-particles were deposited on the MWCNTs by one-step reduction and the modified electrode was fabricated by a simple drop-casting approach. The structure and morphology of Pd/MWCNTs composite were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The composite possesses an appreciable specific surface area, demonstrated unsurpassed electrochemical performance in the oxidation of AP. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were performed to investigate the electrochemical behavior of AP on the surface of modified electrode. The oxidation peak current of the as prepared sensor showed an acceptable linear response from 0.5µM up to 100 µM with a detect limit of 0.13 µM(S/N=3). Additionally, The proposed sensor displayed a good recovery in real sample detection. The excellent electrochemical behavior toward oxidation of AP designates that Pd/MWCNTs composite potentially provides a promising platform for facile fabrication acetaminophen sensor and further application.

Figure 1
Porphyrin-Based Nanomaterials: Enhanced Electrochemiluminescence and the Application of Bioassay
Authors: Shan Dan , Zhang Guang-Yao , Cai Wen-Rong , Xin Wen-Li
Published: February 2020

Electrochemiluminescence (ECL) has become a powerful analytical tool and has been widely applied in many fields. However, ECL still has shortcomings like poor ability to repeatedly electrochemically cycle an individual luminophore, a broad emission spectroscopy, and signal loss due to ECL reagents leaving the detection zone. Therefore, further improvement of ECL signal is still of significance. Nanomaterials can be incorporated into ECL sensor to improve efficiency, but also represent a new class of ECL emitters.

Porphyrins are 18p aromatic azaannulenes consisting of regularly arranged four methine carbons. Electrochemical and photochemical properties of porphyrins have attracted much attention for decades because of their unique aromatic structure and their beneficial characteristics such as high molar absorptivity, as well as the vital roles in biological processes such as photosynthesis, oxygen transport, and biocatalysis. Porphyrins have a flexible and adjustable molecular structure in chemical modification. The introduction of molecular-recognition motifs (e.g., hydrogen bonding, metal-ligand bonds andp-pstacking) into the porphyrin building blocks will make them form new structures, such as fibers, cubes, sheets, simple micelles and wheels. In our work, we have developed several enhanced ECL sensors based on porphyrin-nanocomposite.

For example, we synthesized zirconium-based porphyrinic metal−organic framework (MOF) for the detection of a phosphoprotein. The active center ZnTCPP in MOF-525-Zn as electron media reacts with O2 in the 3D nanocage to produce 1O2, resulting in enhanced ECL signal.

Figure 1
Wearable Tattoo-Based Iontophoretic Biosensing System for Noninvasive Metabolite Monitoring Application
Authors: Kim Jayoung , Wang Joseph
Published: February 2020

In this work, we demonstrate a wearable tattoo based iontophoretic biosensing system for non-invasive metabolite monitoring application. The epidermal sensor device includes an iontophoretic biosensing temporary tattoo system with flexible wireless electronics. The wearable prototype allows noninvasive biofluid sampling via iontophoresis and amperometric detection of metabolite using enzyme and Prussian blue transducer. On-body results with human subjects show distinct differences in the current response reflecting blood metabolite concentration. The data was transmitted wirelessly in real time via Bluetooth communication. The new wireless epidermal iontophoretic-biosensing system offers considerable promise for noninvasive metabolite monitoring in practical settings and can be readily expanded toward the monitoring of additional analytes.
Comparison of Pathogens Capture By Different Bio-Receptors Immobilized Biomolecular Filter in a Large Volume of Liquid
Authors: Du Songtao , Chen I-Hsuan , Liu Yuzhe , Xi Jianguo , Lu Xu , Horikawa Shin , Huang Tung-Shi , Suh Sang-Jin , Chin Bryan A.
Published: February 2020

Foodborne illness is a common public health problem because food can be contaminated by pathogens at any point from farm to dinner table. This paper shows a comparison of capturing a small quantity of a specific bacterial pathogen in a large volume of liquid using a biomolecular filter immobilized with different bioreceptors. The filter consists of support frames, which are made of a soft magnetic material, and solenoid coils for magnetization/demagnetization of the frames. The biomolecular filter is a planar, multi-layered arrangement of strip-shaped magnetoelastic (ME) biosensors with bioreceptor immobilization. These ME biosensors are magnetically held and arrayed on the filter frames. The pathogen of interest in a large volume of liquid is captured by the bioreceptor immobilized on the ME biosensors, when a large volume of liquid passes through. At the same time, non-specific debris can be passed through the biomolecular filter, in order to avoiding a common clogging issue from conventional bead filters. In this work, E2 phage and antibody, are immobilized each on ME biosensors to capture Salmonella Typhimurium in a large volume of water. The capture efficiencies and effects of multiplication of filter layers with E2 phage and the antibody on Salmonella capture efficiency will be discussed.
Bacteriophage-Assisted Magnetic Separation and Electrochemical Detection of Pathogenic Bacteria from Food Matrix
Authors: Ghuman Alyssa , Zhou Yan , Ramasamy Ramaraja P.
Published: February 2020

Foodborne illnesses caused by pathogenic microorganisms are a major threat to worldwide public health. Listeria monocytogenes is among the most common pathogens contributing to domestically acquired foodborne illnesses (1). Most foodborne cases of listeriosis present as life-threatening illnesses in the forms of neonatal listeriosis, blood stream infection, and meningoencephalitis. There is a high priority amongst public health officials to identify Listeria outbreak sources and reduce mortality rates of this disease (2). Since the current methods for bacteria enrichment are time consuming and require sophisticated instruments, they are impossible to reproduce in a non-laboratory setting. There is a growing need to develop field-deployable technologies that are able to rapidly and accurately detect harmful pathogens in complex food matrices such as milk, juice, vegetables, meat, and poultry (3, 4).

This work describes a microfluidic cell sorting device that uses magnetophoresis to detect, separate, and concentrate tagged Listeria monocytogenes from food samples. Bacteriophage-functionalized magnetic particles will be used to isolate the bacteria in a food sample for pre-enrichment, which will allow for more rapid and selective cell sorting followed by impedimetric detection of Listeria in an electrochemical cell. We will report on the effects of flow rate and viscosity of the sample feed on the separation efficiency, as well as the throughput of enriched target bacteria from different food matrices. These enriched samples will be used in various biosensor applications for detection and identification of pathogenic bacteria in food samples.

References

E. Scallan, R. M. Hoekstra, F. J. Angulo, R. V. Tauxe, M. A. Widdowson, S. L. Roy, J. L. Jones and P. M. Griffin, Emerg Infect Dis, 17, 7 (2011).

B. Swaminathan and P. Gerner-Smidt, Microbes Infect, 9, 1236 (2007).

X. Weng and S. Neethirajan, Trends in Food Science & Technology, 65, 10 (2017).

Y. Jiang, S. Zou and X. Cao, Anal. Methods, 8, 6668 (2016).
Viscoelastic Properties of Nanoconfined Water Film and the Role of Alkali Salts
Authors: Khan Shah Haidar , Hoffmann Peter Manfred
Published: February 2020

Nanoconfined water plays an important role in many areas of research such as oil recovery or molecular biology. However, the mechanics and dynamics of nanoconfined water are not well understood. Using an ultra-sensitive homebuilt atomic force microscope, we have shown that pure water film (ρ = 18 MΩ-cm) exhibits squeeze rate dependent viscoelastic properties, and a solid-like behavior at a squeeze rate ≥ 0.8 nm/s, as manifested by an increased Maxwell’s relaxation time (Phys. Rev. Lett. 2010). The introduction of NaCl to the film enhances this tendency by showing the solid-like behavior even at a lower squeeze rate of 0.2 nm/s, as well as extending the range of ordering of water molecules along a mica surface (Langmuir 2016). Here, we will discuss these results as well as the changes introduced by another alkali salt (CsCl) to form a collective picture of the role played by alkali salts in shaping the dynamic mechanical response of nanoconfined water film.
Voltammetry of Valrubicin Quanticles
Authors: Miller Steven T , Trieu Vuong N
Published: February 2020

Valrubicin (N-trifluoroacetyladriamycin-14-valerate) is a chemotherapy drug employed in the treatment of bladder cancer. It is currently available as Valstar®, a Cremophor-EL based formulation for intravesicular administration. At LipoMedics, we have developed a unique nanomedicinization process for water insoluble drugs using a combination of solvents and polymers we named quanticles. Here we report on the synthesis of valrubicin quanticles using phospholipid as polymer. Characterization includes particle size, drug incorporation, zeta potential and electrochemical analysis.

A series of stable phospholipid bound valrubicin quanticles were created using various combinations of PC6 (1,2-dihexanoyl-sn-glycero-3-phosphocholine), PC10 (1,2-didecanoyl-sn-glycero-3-phosphocholine), lysoPC10 (1-decanoyl-2-hydroxy-sn-glycero-3-phosphocholine) and cholesteryl oleate. Two methods of fabricating these quanticles were employed: high pressure homogenization and thin film evaporation. While characteristics like particle size and drug incorporation are similar, the methods result in formulations differing not only in their zeta potential but also in their voltammograms which indicate the formulations are either high capacitance material or low capacitance material.

As previously demonstrated with quanticles of paclitaxel, these quanticles can be distinguished by their zeta potentials and their voltammograms. Therefore, it appears to be the method of formulation that generates an ionic liquid capacitance material with distinctive high or low capacitive voltammic activity. In contrast to the previous work with paclitaxel, valrubicin adds its voltammic signature to the readings of the high capacitive material. A similar signature has not been detected in formulations of low capacitance material.
Electrochemical Detection of the Molecules of Life
Authors: Thomson Seamus David , Koehne Jessica E.
Published: February 2020

Electrochemical sensor devices are of interest in planetary exploration missions where detection of life is a goal. All forms of life on Earth contain cellular machinery that can transform and regulate chemical energy through metabolic pathways. These processes are oxidation-reduction reactions that are performed by four key classes of molecules: flavins, nicotinamides, porphyrins, and quinones (Crawford, 2001). Electrochemical redox may prove a valuable technique for identifying and differentiating these biomolecules and become a useful tool in future life-detecting missions. In this study, we used cyclic voltammetry (CV) and differential pulse voltammetry (DPV) to measure these molecules in a 3D printed flow cell. Electrodes were fabricated from metal wires and interfaced with the flow cell through compression fittings. Glassy carbon (GC) and boron-doped diamond (BDD) electrodes were chosen as working electrodes and used to detect flavin adenine dinucleotide (FAD), riboflavin, plumbagin, anthraquinone, protoporphyrin IX and nicotinamide adenine dinucleotide (NAD). All procedures were performed in a synthetic sea water solution with a Ag/AgCl reference electrode and a platinum wire counter electrode. Limits of detection down to 10 nM were achieved by the GCE. The wide potential window of BDD proved successful in the detection all four classes of redox-active molecules in complex mixtures. Introduction of electrodes into the 3D-printed flow-cell resulted in reliable CV and DPV data, and present this electrode-integrated system as a robust device suitable for future life-detection missions.

Crawford, R. (2001). In Search of the Molecules of Life. Icarus, 154(2), 531–539. https://doi.org/10.1006/icar.2001.6714