bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards Sustainable Energy Storage Via Incorporation of Organic Molecules on Carbon Spheres
Authors: Boota Muhammad , Hatzell Kelsey B. , Kumbur Emin Caglan , Gogotsi Yury
Published: February 2020

Large scale energy storage at lower cost using environmentally benign materials is becoming important due to increasing fraction of electrical energy generation from intermittent renewable energy sources such as wind, solar, and hydro, to name a few. Recently, our group reported on a novel grid-scale energy storage concept named electrochemical flow capacitor (EFC), which takes advantage of both supercapacitors (excellent cycle life, ultrafast charging/discharging) and flow batteries (scalable architecture).1 EFC utilizes the flowable/suspension electrodes composed of electrolyte, electronically conducting active material and, eventually, conductive additives which facilitate the charge transport throughout the suspension network.2–4

Due to the capacitive charge storage mechanism, EFC shows a lower energy density in comparison to batteries. To address this issue, we incorporated small organic redox molecule (hydroquinone), which is inexpensive, non-toxic and offers a highly reversible two-electron two-proton redox reaction.5 Addition of hydroquinone (HQ) molecules adds faradic contribution, which enhances the capacitance and energy density of the flowable electrodes.6We incorporated HQ by mixing HQ with carbon spheres, where HQ was physisorbed on the surface as well as inside the pores of the spheres and by using it as a redox mediator with varying concentrations. The incorporation of HQ was characterized via various microscopic and electrochemical techniques. Carbon spheres with physisorbed HQ molecules exhibited enhanced capacitance of 342 F/g, which was twice as high as that of the carbon slurry (160 F/g). We also observed the increase in capacitance when HQ was used as redox mediator, however this composition showed a poor cycle life. The best performing electrode in the static mode was further examined under intermittent flow mode, and a two-fold higher capacitance was observed.

References:

1. V. Presser et al., Adv. Energy Mater., 2, 895–902 (2012)

2. M. Boota et al., J. Electrochem. Soc., 161, A1078–A1083 (2014)

3. C. Zhang et al., Carbon, 77, 155–164 (2014)

4. K. B. Hatzell et al., ACS Appl. Mater. Interfaces, 6, 8886–8893 (2014)

5. B. Huskinson et al., Nature, 505, 195–8 (2014)

6. M. Boota et al., (Submitted), (2014).
Redox Flow Lithium-Ion Batteries for Large-Scale Energy Storage
Authors: Huang Qizhao , Jia Chuankun , Pan Feng , Wang Qing
Published: February 2020

Based on the discovery of reversible redox targeting reactions of battery materials1, we have recently reported a conceptually new device — redox flow lithium battery (RFLB)2 for large-scale energy storage. In RFLB, the active materials are kept in separate containers without attaching to the current collectors. Upon operation, the exchange of electrons between the materials and current collectors is mediated by the flow of redox shuttle molecules dissolved in the electrolyte fluids via redox targeting reactions. With the cathodic and anodic lithium-ion battery materials LiFePO4
2 and TiO2
3 as an example, we have demonstrated that both materials could be chemically delithiated and lithiated reversibly in the presence of suitable redox mediators. Since the concentrations of Li+ in both materials are as high as 22 M, around 10 times tank energy density could be achieved compared with the conventional vanadium redox-flow battery. 

In our previous study, we have demonstrated RFLB half-cells. Here we report our latest progress in the development of RFLB full systems. This comprises the development of robust redox mediators for both anode and cathode, Li+-conducting membranes, as well as mechanistic studies on the Li+-coupled heterogeneous charge transfer — the essential process for the operation of RFLB. With the above efforts, we have successfully fabricated the first RFLB full cell with LiFePO4 and TiO2 as the cathodic and anodic Li-storage materials, respectively. The system functions with power generated in the cell via the redox reactions of shuttle molecules dissolved in the catholyte and anolyte, while energy stored in the two Li-storage materials, which are kept in two separate energy tanks. RFLB combines the great system flexibility (decoupled power and energy units) of redox flow battery with the high energy density (the same Li-storage materials while no conducting additives and binder required) of lithium-ion batteries, revealing significant potential to its application for large-scale stationary and automotive energy storage.4

References:

Q. Wang, et al., Redox Targeting of Insulating Electrode Materials: A New Approach to High Energy Density Batteries. Angew. Chem. Int. Ed., 45 (2006), 8197-8200.

Q. Huang, et al., Reversible Chemical Delithiation/ Lithiation of LiFePO4: Towards A Redox Flow Lithium-ion Battery.  Phys. Chem. Chem. Phys., 15 (2013), 1793-1797.

F. Pan, et al., Redox Targeting of Anatase TiO₂ for Redox Flow Lithium-ion Battery, Adv. Energy Mater., 4 (2014), 1400567.

Q. Huang and Q. Wang, Next-Generation, High-Energy-Density Redox Flow Batteries. ChemPlusChem, (2014), in press. (doi: 10.1002/cplu.201402099)

Figure 1
Properties of Redox Couples for Use in Organic Redox Flow Batteries
Authors: Hoober-Burkhardt Lena , Yang Bo , Krishnamoorthy Sankarganesh , Prakash G. K. Surya , Narayanan S. R.
Published: February 2020

With penetration levels of renewable energy sources, such as wind and solar, nearing 33% in many places, large-scale energy storage is desperately needed. Organic redox flow batteries (ORBAT), based on water-soluble quinone and anthraquinone derivatives, are a promising solution, as they meet the demanding requirements for large-scale energy storage [1-3]. ORBAT is environmentally friendly, easily scalable, highly efficient, and have low cost. These systems have the potential to meet the DoE cost target of $100/kWh.  

Organic molecules, such as quinones,  are ideal for an aqueous redox flow battery system based not only on their fast kinetics and high capacity, but also because they can be tuned for solubility and electrode potential. Addition of substituent groups affects not only solubility and electrode potential but also the kinetics and mechanism of the redox  reactions. We will present the chemical and electrochemical properties of various molecules that were studied to  understand the effect of substituents.

We will also present our current understanding of any chemical transformations that these compounds undergo during the cycling process. We have followed these changes using electrochemical and spectroscopic techniques.

The results in Figure 1a suggest that as more charge was added, the oxidation current increased, indicating the transfer from oxidized to reduced species, which is as expected for anthraquinone 2,6-disulfonic acid.

However, the 4,5-dihydroxy-1,3-benzenedisulfonic acid molecule undergoes a chemical reaction, known as Michael addition, that changes the composition of the starting molecules, and thus changes the cycling characteristics of ORBAT. This transformation can be seen in the persistent reduced state of the positive side material in Figure 1b.

Understanding the kinetics of the reactions of the redox molecules in water is of utmost importance in ensuring chemical reversibility, high efficiency and high capacity necessary for a useful ORBAT system.

Acknowledgement

The work presented here was funded by ARPA-E Open FOA (DE-AR0000353) and the University of Southern California.

References:

1)Yang, B.; Hoober-Burkhardt, L.E.; Wang, F.; Prakash, G.K.S.; Narayanan, S.R. (2013) J. Electrochem. Soc.
2014, 161, A1371

2)Yang, B.; Hoober-Burkhardt, L.E.; Prakash, G.K.S.; Narayanan, S.R. 224th ECS Conference, San Francisco, CA (2013)

3) Yang, B.; Hoober-Burkhardt, L.E.; Prakash, G.K.S.; Narayanan, S.R. 225th ECS Conference, Orlando, Fl (2013)

Figure 1
(Invited) Electrochemical Detection of Collisions of Single Soft Nanoparticles-Emulsions and Viruses
Authors: Bard Allen J. , Kim Byung-Kwon , Boika Aliaksei , Dick Jeffrey E.
Published: February 2020

Research on nanoparticle (NP) collisions with an ultramicroelectrode (UME) has been extended to “soft” NPs, like emulsion droplets and viruses.  The electrochemical response and the frequency of collisions allow one to extract information about the NPs and even study electrode reactions in fL and aL droplet reactors.   It also allows working with solvents, like toluene, that are not frequently employed for electrochemical reactions and to obtain information about ion transfer across water/oil interfaces.   These studies also allow one to detect rather subtle changes in diffusion coefficient of viruses.
(Invited) Designer Electrochemical Biosensors: Developing Guidelines Driven By Bioanalytical Applications
Authors: White Ryan Jeffrey
Published: February 2020

Biosensors promise to impact many fields ranging from basic research of biological systems to the development of biomedical devices poised to revolutionize modern healthcare. The number of methods for developing biosensors continues to grow at an impressive rate representing the cutting-edge interface of chemistry and many other fields. This talk takes a step back to understand the fundamentals of sensor performance of a class of electrochemical-based sensors. We utilize a combination of electrochemistry, biochemistry, and biomolecular design and engineering to build better biosensors. By developing models for the electrochemical response and understanding the structure and function of nucleic acids (e.g., aptamers) and proteins (e.g., ion channels) we can tune the response of a sensor based on the bioanalytical application of the sensor. Coupling these designer sensors with micro- and nanoscale electrodes further enables us to tune sensor performance for applications ranging from single-cell analysis to implantable devices for real-time therapeutic monitoring.
Interpreting Impedance Spectra in Time-Constant Domain: Application to the Passive Film on Titanium
Authors: Ni Qing , Thorpe Steven J. , Kirk Donald W.
Published: February 2020

Electrochemical impedance spectroscopy (EIS) is a useful method for characterizing the interfacial characteristics of materials such as a passive layer underneath the surface of a titanium-based metal-oxide anode. Conventionally EIS data were interpreted by fitting them with electrically equivalent circuit.  However, this method requires the initial knowledge of the structure of the tested material. It is also impossible to model a system with continuous variation of layers. Normally, an electrode with finite dielectric layers can be represented by a series of RC circuits plus an interfacial impedance. To cope with the difficulty of systems with continuous variation, a distribution function may be assumed to describe the distribution of time constant along the thickness of the layers [1]. Still, this approach needs to assume a profile to which the system is restricted.

A reverse approach was proposed [2]. Within a layered material, a distribution function g(τ) of the resistance over the time-constant (τ=RC) may result from the discrete or continuous variation of the composition (Figure1). By simply fitting the EIS data into Equation 1, one may obtain the function g(τ), which is directly related to the layered structures of the electrode.

This method was previously applied to study a transient passive layer in the Ti-supported metal oxide anode, and showed a continuum over the time constant spectrum [2]. However, direct correlation between the bands and the physically observed layers was not well established. Thus the interpretation method by time-constant domain needs to be validated. In the present work, the growth of a titanium oxide film on top of Ti was studied. This reaction is well studied. The growth kinetics and characterization of the titanium oxide film is well established [3]. Therefore it is considered to be a suitable system to test and validate the use of time-constant spectra for the interpretation of EIS.

Commercially pure titanium was polarized in a pH=7 buffer containing phosphate. Preliminary data confirmed that the system showed the growth of a resistance band with a characteristic time constant (Figure 2). This band is different from the other peak representing the surface charge-transfer process. Its position was almost stationary at all voltages. Judging by its increase, it was considered to be related to the dielectric film developed on top of the Ti. Further work will focus on correlating the data with physical data, including thickness and composition information from the literature.

References

[1] B. Hirschorn, M. E. Orazem, B. Tribollet, et al, Electrochim. Act., 55, 6218 (2010).

[2] Q. Ni, D. W. Kirk and S. J. Thorpe, J. Electrochem. Soc., 162, H40 (2015).

[3] J. F. Vanhumbeeck and J. Proost, Corrosion Rev., 27, 117 (2009).

Figure 1
Quantifying Single Human Cancer Cell Redox State By Scanning Electrochemical Microscopy
Authors: Kuss Sabine , Trinh Dao , Mauzeroll Janine
Published: February 2020

Scanning electrochemical microscopy (SECM) is increasingly applied to study and image live cells. Quantitative analyses of biological systems, however, still remain challenging. In the presented study, single human adenocarcinoma cervical cancer cells are electrochemically investigated by means of SECM. The target cell’s electrochemical signal is observed over time under the influence of green tea catechins (GTC), which are suggested to offer chemopreventive and therapeutic effects on cancer.1 The electrochemical response of living target cells is measured experimentally and the cell’s heterogeneous rate constant is determined by using a numerical model, based on forced convection during high speed SECM imaging. The beneficial effect of GTC on cancer cells could be confirmed by SECM and the presented study shows an alternative approach towards unravelling the mechanisms involved during inhibition of carcinogenesis.

1Connors, SK, Chornokur, G, Kumar NB (2012) Nutrition and Cancer, 64:4.

Figure 1
Redox Triggered Vesicles a Promising Approach for Drug Delivery
Authors: Noyhouzer Tomer , L'Homme Chloé , Kuss Sabine , Kraatz Heinz-Bernhard , Canesi Sylvain , Mauzeroll Janine
Published: February 2020

Drug delivery systems are one of the biggest challenges and emerging fields in the world nowadays. There is a wide interest in developing an efficient method that will be able to transport a biologically active material to a desired location, and then releasing it using a simple process. From the different approaches that tried to overcome the different developing challenges only four nanoparticle-based drug delivery platforms were approved by the Food and Drug Administration (FDA).

 We present here a novel design of a smart drug delivery liposomes based on the use of redox active phospholipids. The redox triggering is very sensitive to small and local changes; therefore it can be applied without affecting other species in the environment as opposed to pH, temperature, ultrasound and photochemistry changes. The system was characterized using advanced methods such as SECM, TEM, DLS and immunoarray fluorescent imaging. Furthermore, when loading the vesicles with anti-cancer medicine and exposing them to live cell we show that the redox induced payload mechanism is fully functional making it a promising candidate for a fully functional drug delivery system

Figure 1
Electrochemical Sensors for Continuous Monitoring of Bacterial Infections
Authors: Goluch Edgar D. , Webster Thaddaeus A. , Sismaet Hunter J.
Published: February 2020

The Infectious Diseases Society of America recently named six pathogens as the greatest threat to modern day medicine as they currently account for over two thirds of all hospital acquired infections and have the ability to rapidly develop antibiotic resistance. While pharmaceutical companies work to develop new antimicrobial compounds to treat infections, one of the best ways to prevent the emergence of antibiotic resistance, and improve patient outcomes, is early detection followed by fast identification and treatment with targeted antibiotics.

To this end, we are developing electrochemical sensors that will be able to continuously monitor patient wounds for signs of infection. Our detection mechanism uses virulence factors that are excreted by pathogens into their local environment. One such approach measures production of pyocyanin by Pseudomonas aeruginosa, a quorum-sensing molecule that is unique to this species and linked to biofilm formation. As pyocyanin is redox-active, it can be detected electrochemically using standard techniques such as square wave voltammetry (SWV), where the sensitivity of the measurements is limited by the concentration of pyocyanin present in the sample.

Since demonstrating the initial concept, we have focused on improving the sensing system and developing new applications for it within healthcare settings. Here, we will present our recent findings for how it may be possible to improve the sensitivity of the system by coating the electrodes with compounds that cause cells to up-regulate the production of pyocyanin. We have also investigated whether pyocyanin production rates are affected by antibiotic treatment. We will show that a simple electrochemical sensor can be used to provide quantitative information about the efficacy of antibiotic treatment regimes for P. aeruginosa infections. We measured the concentration of pyocyanin surrounding biofilms of P. aeruginosa cells while exposing them to a range of antibiotic concentrations. Figure 1 shows SWVs of Escherichia coli and P. aeruginosa biofilms grown in trypticase soy broth (TSB) for A) 0 hr, B) 12 hr, then exposed to flowing 100 mg/L colistin sulfate TSB after approximately C) 22 hr, D) 35 hr, E) 40 hr, and F) 45 hr. The baseline current for the blank TSB was subtracted from the data shown. SWV performed from -0.5 to 0.2 volts at a frequency of 15 Hz and an amplitude voltage of 50 mV. The E. coli cells do not produce pyocyanin and, therefore, no peak is seen in the current around -0.25 volts. The results show that pyocyanin concentration decreases as cells in the biofilm are killed, and therefore can be used to monitor the effectiveness of treatment.

This work was supported by the U.S. National Science Foundation under Grant #1125535.

Figure 1
(Europe Section Alessandro Volta Medal) Electrochemical SERS on Nanostructured Surfaces and its Application to DNA Detection and Discrimination
Authors: Bartlett Philip N.
Published: February 2020

Electroplating through self-assembled templates formed from close packed arrays of uniform colloidal particles allows the controlled deposition of thin films of metals that contain regular hexagonal  arrays of uniform pores. The size of these pores can be systematically varied by varying the size of the colloidal particles and the thickness of the film by controlling the charge passed in the deposition. Removal of the template leaves a supported thin film containing an array of interconnected spherical segment voids.  These sphere segment void (SSV) nanostructured films are ideally suited electrode surfaces for SERS because the structures are robust and reproducible and because the plasmonics of the surface are controlled by the geometry. We have investigated the origins of

the surface enhancement on SSV surfaces by varying the film thickness and template sphere diameter and by looking at the angular dependence. The intensity of the SER spectra varies with all of these factors indicating that the precise geometry of the structured surface and the excitation of surface plasmons is important [1]. These surfaces can be used for practical applications in SERS, for example in in situ electrochemical studies [2].

Combining the extreme surface sensitivity of SERS with control of the electrode potential we have been able to use these SSV electrodes as a platform for very sensitive detection and discrimination of DNA sequences [3].  This new method uses a probe DNA strand bound to the gold SSV electrode surface and then uses the SERS to detect the presence of double stranded DNA formed when the target DNA binds to the probe strand at the surface.  By sweeping the applied potential cathodic the dsDNA strands can be made to separate and the potential at which this separation occurs can be used to discriminate perfectly matched dsDNA from mismatched cases thus allowing discrimination of single nucleotide polymorphisms (SNPs) and short tandem repeats (STRs) [4]. 

References

[1] P. N. Bartlett, J. J. Baumberg, S. Coyle and M. Abdelsalem, Faraday Discuss. 2004, 125, 117.

[2] M. Abdelsalam, P. N. Bartlett, A. E. Russell, J. J. Baumberg, E. J. Calvo, N. G. Tognalli and A. Fainstein, Langmuir 2008, 24, 7018.

[3] S. Mahajan, J. Richardson, T. Brown, and P. N. Bartlett, J. Am. Chem. Soc. 2008, 130, 15589.

[4] D. K. Corrigan, N. Gale, T. Brown and P. N. Bartlett, “Analysis of short tandem repeats (STRs) using SERS monitoring and electrochemical melting”, Angew. Chemie, Int. Edn., 2010, 24, 5917.

Figure 1
Order and Epitaxy during Electrochemical Layer By Layer Growth of Semiconductor Thin Films
Authors: Carlà Francesco , Felici Roberto , Magrini Andrea
Published: February 2020

Electrochemical Atomic Layer Epitaxy (ECALE), also known as Electrochemical Atomic Layer Deposition (E-ALD) [1], is a method based on Under Potential Deposition (UPD) which allows the layer by layer growth of compounds on single crystal substrates.In the ECALE method [1] a compound can be deposited on a substrate by an alternate UPD of the elements that form the compound. UPD is a surface- limited phenomenon, so the electrodeposition in UPD conditions is generally limited to one atomic layer. ECALE has been demonstrated to be a very effective method for the production of thin films of semiconductor compounds with high grade of crystallinity [2-3]. UPD processes on single crystals are substrate dependent, thus different structures of the deposited layer should be expected on substrates with different orientation. Substrate orientation dependency was shown in a previous investigation on the deposition of CdS films on Ag(111), Ag(110) and Ag(100) [2]. Aim of the present work was the in-situ characterization of the growth process of CdS thin films on Ag(111). In-situ structural characterization of thin films is generally a rather complex task as it requires high brilliance x-ray sources given the small thickness of the film, the high background of the electrochemical environment and the attenuation due to the presence of the solvent. Nevertheless synchrotron light sources can provide such an high photon flux to perform this kind of experiment. Surface X-ray diffraction was used to identify the crystallographic structure and to investigate the epitaxial order on the surface. In-situ characterization of the growth process was performed on ID03 beamline at ESRF (Grenoble) using an electrochemical flow cell specifically designed for this purpose. Even if it's well established that the sequential deposition of UPD layers of Cd and S on Ag(111) results in an ordered multilayer structure with lattice parameters comparable to the one of the wurtzite CdS structure [3], several aspects of the growth process were not yet fully understood. In-situ experiments allowed to record structural changes of the in-plane order and details of the out-of-plane relaxation of the film that could not be observed before. One of the most interesting fact observed during the growth process was the dependency of the epitaxial order on the potential used for the UPD deposition of Cd. In figure X-ray reflectivity curve measured during CdS growth on Ag(111).

[1] Gregory and J. L. Stickney, J. Electroanal. Chem. 300, 1991, 543

[2] F. Carla', et al., J. Phys. Chem. C, 12, 6132 (2014)

[3] M.L. Foresti, et al. Electrochimica Acta, 51, 25, 5532 (2006)

Figure 1
Analysis of Electrochemical Reactions on Irregular Pores Structures Relevant to Batteries and Fuel Cells Electrodes
Authors: Okoye Njideka Helen , Liu Yung-way , Arce Pedro E
Published: February 2020

Porous electrodes are important in the applications of fuel cells and batteries by increasing reaction surface area. Systematic understanding of the effect of different pore structures of electro-catalyzed reactions will improve electrode efficiency and, in general, optimize the design of   electrochemical processes occurring in fuel cell and batteries. Electrode systems are analyzed by using models to obtain useful system’s information. This information helps in predicting system level behaviors and assessing experimental results relevant to the design and operation of these pore-based systems. The present work uses analytical models to analyze zero order and first order electrochemical reactions occurring in irregular pore structures applicable for fuel cells and batteries. The electrochemical processes at the electrode pores are modeled by employing the microscopic species mass conservation equation with diffusion in the pore domain and electrochemical reactions present at the boundaries. The microscopic equation is scaled up to the macroscopic pore level by employing an area averaging-based approach to obtain a system level information applicable to practical systems. The area averaged solutions are verified by comparing them with exact solutions based on separation of variables for the ideal cases. Results obtained from the macroscopic equation identified potential deviations in the predicted concentration profiles as the deviation from ideal domains increases. The results predict an important role of the pore geometry on effecting the overall system efficiency as well as the convergence of the averaged solution to the exact solution. This study suggests useful guidelines for modelling and experimentation of complex systems.
Synchronization Patterns of Oscillatory Nickel Dissolution in Microfluidic Flow Cell with Branched Channel
Authors: Liu Yifan , Coleman Jasmine , Kiss Istvan Z
Published: February 2020

Branched microfluidic channels are interconnected to allow for the solution to flow in different streams at different times, which is very attractive for creating complex structures that can be used in analysis, separation, and reaction kinetics. In electrochemical systems, branched flow channels can be used in control networks of chemical reactions and obtain time-resolved measurements of species. In this contribution, we simulate the oscillatory chemical reaction of nickel electrodissolution to explore the interactions through potential drop affecting the temporal variation of current. Mathematical equations were developed for the variation of the dynamical evolution of the electrode potentials and the surface coverage of electroactive species. The synchronization patterns were analyzed through change of coupling strength (k) and placement of electrodes. For each configuration, with increase of coupling strength, a transition from no synchrony through partial synchrony to full synchrony was observed. Close placement of the downstream electrodes to the branching point induces global coupling; under these conditions partial synchronization does not show specific spatial orientation. On the contrary, placement of the downstream electrodes far from branching point induces localized coupling between the upstream electrode and the electrodes in the branched channels. In this case, partial synchronization occurs between the upstream electrode and one of the electrodes in the branched channels. A phase diagram was successfully drawn to predict the synchrony patterns in different geometries. The result has significance in the design of branched microfluidic channel for analytical devices as it shows the extent and type of coupling through potential drop in the electrolyte.
Local Generation of Reactive Oxygen Species at New Polymer-Modified Electrodes
Authors: Wittstock Gunther , Dongmo Saustin , Witt Julia , Dosche Carsten
Published: February 2020

Recently the ability of quinone compound to generate reactive oxygen species has been investigated [1]. The importance of quinone compounds in living organism was widely reported and its therapeutic effect through generation of free radicals has been studied [1-4]. In fact, the efficacy of a monolayer of quinone compound and their polymer film on electrodes to catalyze the reduction of oxygen has been evaluated [1, 2]. It has been mentioned that plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone) possess also cytotoxic properties and has been exploited to produce polymer films which can be used as a controllable source of reactive oxygen species [1]. The two core functionalities of plumbagin allow to produce a redox film and at the same time to preserve the ability of the redox moiety to generate the reactive oxygen species [1]. Nevertheless, in all case the question on the nature of the formed reactive oxygen species generated is still open. In our procedure we obtained stable films of adjustable thickness by first chemically grafting a monolayer of plumbagin to an activated glassy carbon electrode followed by electropolymerization of further layers of plumbagin. These films grew to defined thickness while electropolymerization of plumbagin directly on a glassy carbon electrode led to self-inhibiting insulating films.

The obtained films showed catalytic activity of oxygen reduction. The interest was placed on the generations of hydrogen peroxide and specially superoxide radical with the final aim of design a microscopic generator for future scanning electrochemical microscopic study. The generation of hydrogen peroxide and possible generation of superoxide radical were monitored with lateral resolution by fluorescence microscopy coupled with the high speed camera and by chronoamperometric detection using biosensor based on cytochrome c.

References

[1] L. A. A. Newton, E. Cowham, D. G. Sharp, R. Leslie and J. Davis, New J. Chem.
34, 2010, 395–397.

[2] M.M. Ardakani, P.E. Karami, H.R. Zare and M. Hamzehloo, Microchim. Acta.
159, 2010, 165-173.

[3] H.Shimada, Y.Yamaoka, R. Morita, T.Mizuno, K.Gotoh, T. Higuchi, T. Shiraishi and Y.Imamura, Toxicology in Vitro
26, 2012, 252-257.

[4] V.Sivakumar, R.Prakash, M.R. Murali, H.Devaraj and S.N.Devaraj, Drug and Chemical Toxicology
28, 2005, 499-507
Composites of Polypyrrole with Micelles Nanospheres
Authors: Gryczan Piotr , Maksymiuk Krzysztof , Kisiel Anna , Michalska Agata
Published: February 2020

Alternating polymers were used to obtain self assembling micelles – nanospheres. In the polymer structure every second unit is maleic anhydride (poly(maleic anhydride alt-1-octadecene)), as upon spontaneous hydrolysis anhydride groups are transformed into carboxyl groups resulting in stability of thus obtained particles (micelles) in aqueous environment [1]. Crosslinking can be achieved in course of reaction with bis(hexamethylene)triamine.

Thus obtained nanospheres have size close to ~150 nm and negative surface charge, due to the presence of carboxyl groups on the surface. The above mentioned structures were incorporated into polypyrrole films, obtained electrochemically, where micelles with ionized carboxyl groups served as negative counter ions. The polymer was characterized by stable voltammetric responses and  very well separated potential ranges corresponding to anion– and cation–exchanging properties (in contrast to classical polypyrrole / polystyrenesulfonate films, where overlapping of these ranges was observed). Potentiometric sensitivity of these films can be switched between anionic and cationic characteristics by appropriate conditioning / polarization. Polypyrrole / nanospheres composites exhibit also significant pH sensitivity both in voltammetric and potentiometric mode, resulting from the presence of carboxyl groups.

Controllable sensitivity to various groups of ions and possibility of ions accumulation is promising for analytical applications of these composites, because of the fact that nanospheres can be loaded with compounds of choice, e.g. ionophores or catalytic centers [2].

 

T. Pellegrino, L. Manna, S. Kudera, T. Liedl, D. Koktysh, A. L. Rogach,  S. Keller, J. Rädler,

G. Natile, W. J. Parak, Hydrophobic nanocrystals coated with an amphiphilic polymer shell: a general route to water soluble nanocrystals. Nano Lett.
2004, 4. 703-707.

A. Kisiel, K. Kłucińska, Z. Głębicka, M. Gniadek, K. Maksymiuk, A. Michalska, Alternating polymer micelle nanospheres for optical sensing. Analyst, 2014, 139. 2515-2524.
The Impact of the Alkali Cation on the Oscillatory Electro-Oxidation of Ethylene Glycol on Platinum
Authors: Sitta Elton , Nagao Raphael , Kiss Istvan Z , Varela Hamilton
Published: February 2020

The presence of hydrated alkaline cations in the supporting electrolyte has showed to play a significant role in electrocatalysis. Differently from the specific adsorption of anions, which blocks active sites and/or drive the reaction through different pathways, alkaline cations interact with adsorbed oxygenated species by non-covalent interactions. In this direction, our contribution relies on the understanding of the impact of alkaline cations in the electro-oxidation of ethylene glycol in conventional and oscillatory electrochemical conditions. We were able to extract mechanistic information of the blocking intermediates generated on the surface by the calculation of poisoning reaction rate constant (kp) in oscillatory regime, and additionally, compared with the overall current densities in the voltammetric profiles. Paradoxically, as long as the cation hydration energy decreases (Li+ > Na+ > K+), larger kp values were obtained concomitantly with higher electro-catalytic activities. Although the cation also has a blocking effect by the prevention of the reaction between adsorbed carbonaceous and oxygenated species, numerical simulations suggest that kp is mainly related to the formation of reaction intermediates by C-C bond breaking, while the inhibition of the faradaic current comes from alkaline cations with smaller radius.
Low-Cost, Fused Filament Fabrication-Prepared, 3D-Printed Microfluidic Devices with Modularly Integrated Electrodes for Electroanalytical Measurements
Authors: Bishop Gregory William , Satterwhite Jennifer E , Bhakta Snehasis , Rusling James F
Published: February 2020

Decreasing costs, improving availability, and the introduction of new materials for 3D printing technologies have resulted in more extensive applications of 3D printing in chemical and biochemical research. Recently, 3D printing has been used to make microfluidic devices for chemical mixing, gradient generation, and sensing applications, including electrochemical sensing via flow-injection amperometry. While several reports of 3D-printed microfluidic devices have appeared, most of these rely on polyjet, multijet, or stereolithography methods that require expensive printers, costly materials, and/or special finishing and post-processing treatments. Here we show that low-cost, easy-to-prepare microfluidic devices, similar to those that have been reported using more expensive 3D printing methods, can be fabricated using a desktop 3D-printer based on inexpensive fused filament fabrication (FFF). We demonstrate that microfluidic devices with threaded openings can be prepared to enable insertion of 3-electrode fittings in the channel for electroanalytical measurements and applications such as sensing based on flow-injection amperometry. These devices feature channels designed to have width and height dimensions ≤800 μm and are semitransparent to allow visualization of the solution-filled channels. The FFF-printed devices described in this work provide a low-cost, simple alternative to the previously reported modular, 3D-printed systems for flow-injection analysis based on polyjet printing.
Manipulation of Nanoscale Pattern Formation in Photoelectrochemically Deposited Chalcogenide Films Using Multiple Beam Illumination
Authors: Carim Azhar , Batara Nicholas , Premkumar Anjali , Atwater Harry A , Lewis Nathan S.
Published: February 2020

Photoelectrochemical deposition of semiconducting chalcogenide films resulted in the spontaneous generation of ordered nanostructures wherein the pattern developed is a function of the illumination utilized during growth. Film adopted an ordered, highly anisotropic lamella-type pattern when deposited under conformal illumination with polarized light. Feature size and pitch were controlled the illumination wavelength, direction of anisotropy by the polarization vector and the growth direction by the incident light vector. In order to progress toward generation of intricate, 3-dimensional architectures for specific applications, the manipulation of the pattern formation by utilizing simultaneous illumination from multiple discrete beams during deposition has been investigated. Illumination with two parallel polarized, narrowband sources with two discrete mean wavelengths resulted in patterns with periods that were intermediate of those that would be expected for either source alone and a function of the relative source intensities. The use of two linearly polarized sources with polarization vectors separated by an acute angle produced structures oriented in a direction between the two polarization vectors: this direction was a function of the relative intensities and mean wavelengths of the sources. Illumination with orthogonally polarized sources provided for the generation of mesh-type structures wherein the periodicity and height of pattern in the two orthogonal, in-plane directions could be controlled independently by varying the intensities and wavelengths of the sources.  Modeling of the growth was achieved with a Monte Carlo process wherein the probability of mass-addition was weighted based on simulations of the light-matter interactions in the films.

This photoelectrochemical deposition process is unique from other methods of generating ordered mesostructures with electrochemical means as no photomask, no photoactive substrate, no physically patterned substrate, nor any chemical templating agents (ligands, surfactants) were utilized. Additionally, tuning the deposition potential and electrolyte along with the illumination has enabled control of the material composition. The same general morphology was observed for a range of varying materials. Thus, this process displays significant, increasing potential to possibly enable the generation of complex morphologies for functional materials without some of the limitations imposed by traditional fabrication techniques.
Benchmarking of Heterogeneous CO2 Reduction Reaction Electrocatalysts
Authors: Ferrer Ivonne M. , McCrory Charles C L , Peters Jonas C , Jaramillo Thomas F
Published: February 2020

The identification of earth abundant, efficient electrocatalysts for the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and carbon dioxide reduction reaction (CO2RR) is crucial for the development of solar-fuels devices.  Historically, procedures and conditions used for the evaluation of various electrocatalysts differ from laboratory to laboratory, resulting in performance metrics that are not easily compared. We have developed a benchmarking protocol that allows for the consistent assessment of activity, stability, electrochemically-active surface area and Faradaic efficiencies of electrocatalysts.  Using this benchmarking protocol, we have evaluated the performance of over 50 HER and OER electrocatalyts. The standardized evaluation of OER and HER electrocatalysts has allowed us to identify important trends for the advancement of solar-fuels research. More recently, we have developed electrochemical methods for the standardized analysis of electrocatalysts for CO2RR. This has included the development of analytical methods for standardized identification and quantification of CO2 reduction products. Given the complexity of CO2 reduction reactions and the variety of products that can be formed depending upon the catalyst, product analysis plays a key role on the Benchmarking of CO2 reduction catalysts. Herein, we present benchamrking of CO2RR catalysts and the analytical methods developed for the identification and quantification of liquid and gaseous products.
Calculating the Proton Transport and Dielectric Properties of Phosphates and Related Materials
Authors: Tuckerman Mark E.
Published: February 2020

Phosphate based systems are cosidered to be promising electrolyte materials for use in fuel cells.  It is know, for example, that liquid phosphoric acid has the highest known intrinsic proton conductivity of any substance.   However, little is known about the microscopic mechanisms of proton conduction is phosphate based systems or about their dielectric properties.  In this talk, I will discuss efforts we have made to elucidate these properties in pure phosphoric acid, phosphoric acid with imidazole (as a model for the types of stabilizers often used in phosphoric acid fuel cells) and in related phosphonic anc phosphinic acid systems for comparison.  The approaches used mostly rely on first-principles molecular dynamics calculations, which are able to treat the bond-breaking and forming events associated with proton transport, however, I will also discuss the performance of several force fields applied to these systems, which also allow us to test finite-size effects (system sizes are, by necessity, small in first-principles molecular dynamics calculations) and effecdts of simulation length (simulation lengths are also, by necessity, short in first-principles molecular dynamics)..   As will be discusssed in the talk, by examining diffusion, kinetics, microscopic mechanisms, and dipole distributions, we have garnered considerable new insights into these ccomplex systems.
Mathematical Modeling of Multi-Physics Electrochemical Devices
Authors: Farrell Troy W.
Published: February 2020

Electrochemical devices such as batteries and electrochemical solar cells are often described as multi-physics devices. This is a catch-all term meant to convey the fact that these devices are inherently multi-scale, multi-component and multi-phase in nature and that their operation involves complicated interfacial charge transfer and bulk solid and solution phase charge transport. Consequently, the development of accurate and meaningful mathematical models and numerical simulations for such devices is a complex task. Such modelling however, can play a vital role in the optimization of these devices via the identification of the key parameters that control their operational behaviour for a range of conditions and material configurations.

In this presentation we will consider examples from some of the authors previous(1-10) and current work on the mathematical modelling of multi-physics electrochemical devices such as battery electrodes, solar cells and nano-diodes to highlight the challenges, approaches and outcomes of such modelling.  

REFERENCES

T. W. Farrell, C. P. Please, D. L. S. McElwain and D. A. J. Swinkels, J. Electrochem. Soc., 147, 4034 (2000).

T. W. Farrell and C. P. Please, J. Electrochem. Soc., 152, A1930 (2005).

M.A. Penny, T.W. Farrell and G.D. Will, Sol. Energy Mat. & Sol. Cells, 92, 24-37, 2008.

Troy Farrell and Steven Psaltis, in Physics of Nanostructured Solar Cells, eds. V. Badescu and M. Paulescu, pp. 327-353, Nova Science Publishers, Inc., New York, ISBN: 978-1-60876-110-4, 2010.

S. Dargaville and T.W. Farrell, J. Electrochem. Soc., 157, A830 (2010).

S. T. P. Psaltis and T. W. Farrell, J. Electrochem Soc., 158, A33 (2010).

S. Dargaville and T.W. Farrell, Electrochimica Acta,
94

(1), pp. 143-158 (2013).

S. Dargaville and T.W. Farrell, Electrochimica Acta,
111
, pp. 474-490 (2013).

S. Dargaville and T.W. Farrell, Journal of Computational and Applied Mathematics, 273, pp 255-244 (2014).

S. Psaltis, T. Farrell, K. Burrage, P. McCabe, T. Moroney, I. Turner and S. Mazumder, “Mathematical Modelling of Gas Production and Compositional Shift of a CSG Field: Local Mo del Development”, submitted to Energy (2014).
Simulations of Phase Transformation Dynamics in LiFePO4 Particles in Battery Electrode
Authors: Yu Hui-Chia , Orvananos Bernardo , Akyildiz Oncu , Thornton Katsuyo
Published: February 2020

Lithium iron phosphate (LFP) has been a successful material for Li-ion battery cathodes due to its enhanced safety and rate capability. For cathodes consisting of LFP nanoparticles, the current-voltage response in macroscopic electrochemical measurements exhibits a feature indicative of solid-solid phase transformation during the charge-discharge processes. However, the Li concentration evolution within individual nanoparticles remains to be elucidated.

In this work, we used phase field modeling to investigate the effects of a variety of material parameters and their anisotropies on the morphological evolution of the lithiated and delithiated phases in cathode particles. An elliptical particle of 45 and 35 nm in diameters along the longest and shortest axes was used in the simulations. This particle was assumed to be immersed in electrolyte and to be placed in contact with a current collector. To simulate the lithium concentration evolution during the electrochemical process, six coupled governing equations were solved self-consistently. These equations describe lithium transport in (1) the particle and (2) the electrolyte, electrostatic potential in (3) the particle and (4) the electrolyte, (5) the electrochemical reaction rate at the particle surface, and (6) mechanical equilibrium in the particle.

The highly anisotropic material properties of LFP reported in the literature were adopted as the simulation parameters, including lithium diffusivities, interfacial energies, surface insertion rate, electronic conductivity, misfit strain, and elastic moduli. To examine the individual and combined effects from these parameters, the simulation parameters were altered from the reported values in our parametric studies. By exploring the material parameter space, we found that the anisotropy of electronic conductivity is the dominant factor in determining phase evolution in a bare LFP particle (without conductive coating). In contrast, for a carbon-coated particle, the anisotropy in electronic conductivity loses its significance and the lithiation process becomes more isotropic. 

This work was supported as part of the NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012583.

Figure 1