bluuebunny/crossref_metadata_2025 huggingface dataset:
New Ion-Exchange Membranes Derived from Polyketone
Authors: Di Noto Vito , Nawn Graeme , Vezzù Keti , Bertasi Federico , Negro Enrico , Cavinato Gianni , Pace Giuseppe
Published: February 2020

The centre piece at the heart of numerous energy storage and conversion devices, such as fuel cells and redox flow batteries, is the ion-exchange membrane (IEM). This typically polymeric material is responsible for the migration of ionic species, separation of fuel stocks and for providing additional support to the electrode assemblies. As a result, IEMs are required to possess excellent stability (both thermal and chemical), long lifetimes, electrical insulation, and high ionic conductivity and specificity. Current state-of-the-art polymer electrolytes possessing the more desirable properties tend to come with a price tag that can render their use in energy storage/conversion technologies somewhat cost prohibitive [1]. This has created a strong driving force aimed towards new, cheaper but still high performing materials, for use in energy storage/exchange systems.

The copolymerization of carbon monoxide and ethylene (two readily available and cheap feedstocks) leads to the formation of polyketone, a high performance thermoplastic that has found many applications resulting in its global production of thousands of tonnes per annum. The alternating 1,4-dicarbonyl functionality of aliphatic polyketone enables access, via classic Paal-Knorr chemistry, to a variety of new functionalized polymers [2]. Here we present a new ion conducting polymeric material derived from polyketone, that possess N-functionalized pyrrole units in the backbone (FPK) [3]. Ion-conductivities on the order of 10.6 and 8.6 mScm-1 for the hydroxide and iodide forms of methylated FPKs have been achieved at 80 oC, with the hydroxide FPK demonstrating high resistance towards alkaline conditions for over 20 hours at 80 oC.

The flexibility in the choice of the N-substituent renders these new materials higher tailorable and potentially useful in a range of energy storage/conversion technologies as either proton or anion exchange membranes.

Acknowledgements

The authors wish to thank the Strategic Project of the University of Padova “Materials for Membrane-Electrode Assemblies to Electric Energy Conversion and Storage Devices (MAESTRA)” for funding. V.D.N. thanks the University Carlo III of Madrid for granting him the “Catedra de Excelentia” (Chair of Excellence).

References

[1] S. Eckroad in Handbook of Energy Storage for Transmission or Distribution Applictions, Electric Power Research Institute Report 1007189, California, USA (2002)

[2] A. Sen et al., Macromolecules, 22, (1989), 2012, A.A. Broekhuis et al., J. Apply. Polm. Sci., (2016), 42924, A.A. Broekhuis et al., J. Appl. Polym. Sci., 107, (2008), 107, 262, A.A. Broekhuis, Dyes and Pigments, 98, (2013), 51

[3] N. Ataollahi, K. Vezzù, G. Nawn, G. Pace, G. Cavinato, F. Girardi, P. Scardi, V. Di Noto, R. Di Maggio, Electrochimica Acta., 226 (2017) 148-157.
Synthesis and Properties of s-PBI/2OH-PBI Random Copolymer for High Temperature PEM Fuel Cells
Authors: Lee Ju Sung , Lee Min Jae , Lee So Young , Jang Jong Hyun , Kim Hyoung-Juhn
Published: February 2020

High temperature polymer electrolyte membrane fuel cell (HT PEMFC), which has the advantages of high tolerance to fuel impurities and simplified system according to no humidification, is currently being studied extensively. The phosphoric acid (PA) with proton conductivity at high temperature (150℃) is used as an electrolyte in HT PEMFC. Therefore, the affinity between membrane material and phosphoric acid and membrane durability are very important. At present, membrane material for HT PEMFC is mainly used the polymer based on polybenzimidazole (PBI). However, the PBI has the problems such as low molecular weight, low PA doping level, PA leakage during operation, and membrane durability. According to some studies, sulfonic acid groups and hydroxyl groups have high affinity for phosphoric acid. Therefore, PBI-based polymer electrolyte prepared from each monomer showed improved doping level, proton conductivity and performance. In this study, we tried to fabricate electrolyte membrane for HT PEMFC with improved properties and cell performance by simultaneously introducing these two functional groups.

For the synthesis of s-PBI/2OH-PBI random copolymer, monosodium salt of 2-sulphoterephthalic acid (STA), 2,5-dihydroxyterephthalic acid (2OH-TA) and 3,3'- diaminobenzidine were prepared with ratio of 1:0:1 (10:0), 0.5:0.5:1 (5:5), 0.4:0.6:1 (4:6). The condensation reaction was used for synthesis of copolymer. The polymer membranes were fabricated by direct casting method. The polymer membrane of the fabricated film type was placed in the humidity chamber at each hydrolysis condition. The degree of polymerization of s-PBI/2OH-PBI random copolymer was confirmed by measuring the torque of the polymer solution in real time. The characteristics of the prepared copolymer were analyzed by FT-IR and doping level. Finally, single cell performance according to monomer ratio and hydrolysis condition was evaluated by IV curve measurement.

The IV curves of s-PBI/2OH-PBI random copolymer were affected by monomer ratio and hydrolysis condition. First, the IV curves showed better performance as the monomer ratio of 2OH-TA increased in hydrolysis conditions of 50℃ and RH 50%. Despite the lowest doping level in the 4:6 monomer ratio, the highest cell performance in 4:6 was attributed to the improvement of the mechanical properties with the increase of polymerization degree. On the other hand, the IV curve at 4: 6 monomer ratio showed the best performance in RH 80% and 70% phosphoric acid bath condition. This confirmed that the polyphosphoric acid was only partially hydrolyzed in the RH 50% condition.

Figure 1
Diffusion Layers with Localized Hydrophilic Domains: Influence of Electron Energy on Spatial Resolution
Authors: Forner-Cuenca Antoni , Manzi-Orezzoli Victoria , Gubler Lorenz , Schmidt Thomas J. , Boillat Pierre
Published: February 2020

The development of advanced water management strategies for polymer electrolyte fuel cells (PEFCs) could enable further improvements in power density, and therefore decrease the cost. A recently developed approach, consisting on electron radiation grafting using masks, has been utilized to fabricate gas diffusion layers with patterned wettability [1]. These novel materials feature hydrophilic, straightforward pathways for the transport of liquid water; and hydrophobic, low-resistance domains for the transport of reactant gases [2]. It has been recently demonstrated that PEFCs performance can be improved by employing the modified gas diffusion layers on the cathode side, due to the segregated distribution of liquid water that leads to reduced mass transport overpotentials [3].

However, further improvements in resolution are required to fabricate advanced porous materials with localized properties for various applications [4]. Pursuant to this goal, simulations can be used, in tandem with experiments, to elucidate the dominating parameters that influence the resolution (e.g. electron energy, mask-to-sample separation). Moreover, simulations can be utilized in a predictive fashion to calculate the electron beam parameters required to fabricate a given material. In this presentation, we will discuss the influence of electron beam energy on the spatial resolution of porous materials typically used in PEFCs. A combination of experiments and Monte-Carlo simulations was employed to advance the fundamental understanding of mask-assisted through-volume modifications of thick porous substrates. Interestingly, we found that an energy of, at least, 140 keV was required to modify throughout the complete thickness and that the use of energies lower than 300 keV results in a blurring in the adjacent regions. Additionally, we will discuss the influence of housing materials on the back-scattered radiation. Finally, and due to its practical relevance, we will discuss the possibility of selectively modifying one layer out of a bi-layered material (i.e. GDL-MPL arrangement).

[1] Forner-Cuenca, A. et al., Adv. Mater. 27, 6317–6322 (2015).

[2] Forner-Cuenca, A. et al., J. Electrochem. Soc. 163, F1038–F1048 (2016).

[3] Forner-Cuenca, A. et al., J. Electrochem. Soc. 163, F1389–F1398 (2016).

[4] Forner Cuenca, A. et al., Radiat. Phys. Chem. 135, 133–141 (2017).

Acknowledgments

AFC gratefully acknowledges the financial support of the Swiss National Science Foundation (P2EZP2_172183).
Dispersing Effect of Poly (vinyl pyrrolidone) Addition on Platinum/Tin Phosphate/Carbon Black Bifunctional Catalysts for Direct Methanol Fuel Cell
Authors: Huang Chun Yuan , Cheng Yu Ching , Yen Shiow Kang
Published: February 2020

Direct methanol fuel cells (DMFC) are electrochemical conversion device that can produce electricity at high fuel efficiencies, and Pt the excellent and major catalyst in them, is too expensive to be developed for applications widely. Before large-scale consumer use, three technological problems should be solved. 1. The activity of electrodes should be improved to increase efficiency, and then the amount (i.e. cost) of platinum catalyst in electrodes. 2. Poisoning effects of CO on Pt catalyst should be removed. 3. The conductivity of catalyst should be enhanced to reduce the energy waste in system.

Nano-sized platinum (Pt) particles were successfully reduced on tin phosphate (SnP) precipitated carbon black (C) to form Pt/SnP/C catalysts. In methanol oxidation reaction (MOR), these catalysts revealed the more electrochemical mass activity and less obvious CO poisoning effects than Pt/C to become potential for bi-functional catalysts. However, the serious agglomeration of Pt is observed. In this study, Poly (vinyl pyrrolidone) (PVP) was firstly added dispersed carbon black supports, assigned to C (PAD), to avoid the further agglomeration after SnP precipitation on them for increasing the specific surface area of SnP on which platinum was reduced, and hence enhancing the electrochemical performance as well as detoxifying function.

By using the characterization of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), and inductively coupled plasma-mass spectrometry (ICP-MS), the characterization of catalyst Pt/SnO2-SnP/C (PAD) was carried out.

The particle size of platinum is 4.431 nm by XRD analyses and 3.61~3.97 nm observed by TEM. In hydrogen oxidation reaction (HOR) tests, electrochemical surface area (ECSA) of Pt/SnP/C was 765 (cm2/mg), and that of Pt/SnP/C (PAD) increased to 1268 (cm2/mg). In methanol oxidation reaction (MOR), catalyst Pt/SnP/C (PAD) illustrates the higher mass activity 80.67 (A/gPt, at 0.4 V) and the lower on-set potential 0.2 V (vs. Ag/AgCl). No forward current peaks was observed, indicating the deletion of CO poison effect on Pt than Pt/SnP/C. In membrane electrode assembly (MEA) tests, Pt/SnP/C (PAD) also reveals the greater power density and open circuit voltage than Pt/C (Alfa). TEM observations show that SnP is the nucleation site of Pt which is more dispersed than Pt/SnP/C in catalyst, leading to the better electrochemical performance.
A New Class of Carbon Catalysts for Nitrogen Reduction during NH3 Electrosynthesis
Authors: Mukherjee Shreya , Gupta Shiva , Wu Gang
Published: February 2020

Developing catalyst to facilitate ammonia synthesis was so challenging that it gave Haber and Bosch the Noble prize in 1918. However, the reaction is very energy intensive involving high temperature, high pressure and use of conventional fossil fuels. Sustainable synthesis of ammonia by renewably reducing nitrogen at ambient conditions without using hydrogen as a reactant is an ever growing field of research now; However in presence of water, when a negative potential is applied to reduce nitrogen, hydrogen evolution is favored. Thus, like CO2 reduction, increasing the selectivity of NRR over HER is a major challenge. We focused on identifying and tuning surface of adsorption (electrocatalyst), environment (electrolyte) to minimize HER as much as possible. Here we present a new type of carbon catalysts with Fe doping, which are known to containing FeN4 sites. We observed that higher the metal doping, lower is difference in current density in N2 and Ar atmosphere (dominant HER). Surprisingly, the ammonia detected was higher for very low metal doping. This stimulated us to study the effect of metal doping content on NRR activity and ammonia production rates. Here we report an ammonia production rate of 3.1 x 10-6 mol cm-2hr-1 at -0.3 V vs RHE with new carbon catalysts (and a FE of 30 % using an alkaline electrolyte 0.1 M KOH under ambient conditions. We also tested our catalyst in acidic electrolyte where the FE reduced due to increased HER in a higher concentrated proton environment.
Transition Metal Complexes for Catalytic N2 Reduction and NH3 Oxidation: Strategies for Making and Breaking N≡N and N-H Bonds
Authors: Mock Michael Thomas , Bhattacharya Papri , Kendall Alexander J , Prokopchuk Demyan E , Bullock Morris , Wiedner Eric S.
Published: February 2020

The production of ammonia (NH3) from atmospheric dinitrogen is one of the most important and challenging chemical transformations. In addition to NH3 being invaluable for the production of fertilizers necessary to sustain global agriculture, NH3 is also an appealing nitrogen-based fuel due to its high energy density and ease of storage and distribution. However, producing NH3 from N2 using industrial Haber-Bosch catalysts is a highly energy-intensive process. Developing efficient electrocatalysts for NH3 production from N2, and protons and electrons, could augment this energy intensive process and enable distributed facilities for on-demand NH3 production. Moreover, catalysts for the reverse reaction, NH3 oxidation, will be essential to utilize the energy stored in N-H bonds. This presentation will describe iron and chromium complexes with tetradentate phosphine ligands to catalyze N2 reduction. M-NH3 complexes supported by bidentate phosphine ligands containing non-coordinating pendant amines for the catalytic oxidation of NH3 to N2 will also be discussed. The synthesis and initial electrochemical studies of these systems will be described.
Evaluation of Varying Electrocatalysts for the Intermediate Temperature Electrochemical Synthesis of Ammonia
Authors: Ramaiyan Kannan Pasupathikovil , Maurya Sandip , Benavidez Angelica D , Nayak Shanti Kiran , Kim Yu Seung , Garzon Fernando H , Mukundan Rangachary , Kreller Cortney R.
Published: February 2020

Ammonia synthesis by the Haber-Bosch (HB) process paved the way for rapid increase in crop production and sustained the needs of population growth. However, HB process is cost and energy intensive and releases about 260 million tons of CO2 every year. Considering the threat associated with CO2, finding an alternative, cheap and environmentally benign methodology for ammonia synthesis is highly desirable. Electrochemical synthesis through renewable electricity offers a viable alternative, although the synthesis rates reported are far from adequate. This is mainly due to the strong NºN bond (941 kJ mol-1) that poses a severe challenge for mild condition synthesis of ammonia. Several attempts toward electrosynthesizing ammonia at low and high temperatures included a variety of electrode materials ranging from glassy carbon electrode to precious metals and different proton and oxide ion conducting electrolytes [1]. Rates on the order of 10-9 mols-1cm-2 have been reported for both low and high temperature systems. This rate is still three orders of magnitude lower than the required rates for commercialization.

We have achieved ammonia synthesis rates of 1x10-8 mols-1cm-2 at 200 °C in a simple fuel cell configuration using a Sn2P2O7 – nafion composite membrane and Pt based catalyst [2]. Here we will present our results obtained with alternate electrocatalysts and discuss the role of applied potential and back pressure measurements on the synthesis rates of ammonia.

References

V. Kyriakou, I. Garagounis, e. Vasileiou, A. Vourros, and M. Stoukides, Catalysis Today, 2017, 286, 2-13.

K. P. Ramaiyan, S. Maurya, Y. S. Kim, F. H. Garzon, R. Mukundan, C. R. Kreller, Meeting Abstracts, ECS 231st meeting. Issue 31, 1464-1464.

Acknowledgements

This project is supported by ARPA-E under Award No. DE-AR0000687.
Electrochemical Behavior of 2-Halo-N-Phenylacetamides at a Carbon Cathode
Authors: Couto Petro Ana G. , Peters Dennis G
Published: February 2020

Haloacetamides and haloacetanilides have been utilized for the synthesis of many compounds such as, but not limited to, β-lactams,1
N,N-bis-(phenylcarbamoylmethyl) dimethylammonium,2 and oxazolidine-2,4-diones.3 Therefore, it is important to understand fully how these haloacetamides behave as well as the reaction pathways they undergo. Electrochemical studies of 2-chloro-N-phenylacetamide have been reported at carbon cathodes, and were successful in demonstrating the reductive cleavage of the carbon–halogen bond. A mechanism for the aforementioned reduction has been proposed.4 This project’s primary objective is to compare the electrochemical behavior of a series of 2-halo-N-phenylacetamides and to elucidate a more complete mechanistic picture for the reduction of this class of compounds.

In the present investigation, we have conducted cyclic voltammetry and controlled-potential electrolysis studies of 2-iodo-N-phenylacetamide and 2-bromo-N-phenylacetamide at a carbon cathode to understand further the electrochemical behavior of 2-halo-N-phenylacetamides. Reduction of 2-bromo-N-phenylacetamide and 2-iodo-N-phenylacetamide in dimethylformamide (DMF) containing 0.05 M tetramethylammonium tetrafluoroborate (TMABF4) results in cyclic voltammetry peaks at –0.9 and –1.4 V (bromo) and –0.6 and –1.1 V (iodo) vs. a Cd(Hg) reference electrode. Analysis of the products resulting from controlled-potential electrolyses of both analytes by means of gas chromatography–mass spectrometry (GC–MS) indicates the presence of dehalogenated species as the primary products.

Casadei, M. A.; Di Rienzo, B.; Inesi, A.; Moracci, F. M., Electrochemical studies on haloamides. Part 3. Haloacetamides and halo-acetohydroxamates. J. Chem. Soc., Perkin Trans. 1
1992, 375–378.

Walker, M. J., Treating cough and tussive attacks. Google Patents: 2012.

Casadei, M. A.; Cesa, S.; Inesi, A., Electrochemical studies on haloamides. Part XII. Electrosynthesis of oxazolidine-2,4-diones. Tetrahedron
1995,
51, 5891–5900.

Pasciak, E. M.; Sengupta, A.; Mubarak, M. S.; Raghavachari, K.; Peters, D. G., Electrochemical reduction of 2-chloro-N-phenylacetamides at carbon and silver cathodes in dimethylformamide. Electrochim. Acta
2014,
127, 159–166.
Application of the Cation Pool Method for Fluorination and No-Carrier-Added Radio-Fluorination
Authors: Balandeh Mehrdad , Rios Alejandra , Allison Nathanael , Shirazi Daniela , Sadeghi Saman
Published: February 2020

In 1999 Yoshida and co-workers developed the cation pool method which stabilized carbamate cationic intermediates generated during a two electron oxidation followed by deprotonation that takes place in the anodic compartment of a two compartment cell under low temperatures.1 The method allows for rapid reactions with nucleophiles that may be unstable during electrolysis and can be added to the reaction mixture at the end of electrolysis to form the final product.

Here, we report on the extension of the cation pool method for the application of electrochemical fluorination and radio-fluorination of methyl (phenylthio)acetate. Electrochemical fluorination and no-carrier-added radio-fluorination were successfully achieved using the cation pool method . Figure 1 shows the schematic of no-carrier-added electrochemical radio-fluorination of methyl (phenylthio)acetate using cation pool method. The cation pool method has tremendous potential for radiofluorination experiments. The excess concentration of cations may provide an efficient reaction mechanism for late-stage fluorination under low fluoride concentrations encountered in radiochemistry. Furthermore, radiochemical yield, which is reduced by decay of the radioisotope, can benefit from a rapid late-stage fluorination reaction. The cation pool can be prepared prior to cyclotron production of 18F isotope, thereby, providing a rapid late-stage fluorination reaction, maximizing radiochemical yield by minimizing decay through a rapid reaction of the previously prepared cations with 18F-fluoride.

Synthesis parameters such as temperature, supporting electrolyte concentration and type, and precursor concentration were studied and optimized. The fluorination and radiofluorination yields of 12% and 6.7% were obtained, respectively, using the optimum conditions. The products were characterized using gas chromatography–mass spectrometry (GC-MS), nuclear magnetic resonance (NMR), radio-thin-layer chromatography (radio-TLC) and high-performance liquid chromatography (HPLC). This method can also be applied for a late-stage no-carrier-added radiofluorination to develop new positron emission tomography (PET) tracers.

Figure 1. Schematic of no-carrier-added electrochemical 18F-fluorination of methyl (phenylthio)acetate using cation pool method.

References

Yoshida, J. et al. Direct Oxidative Carbon−Carbon Bond Formation Using the “Cation Pool” Method. 1. Generation of Iminium Cation Pools and Their Reaction with Carbon Nucleophiles. J. Am. Chem. Soc.
121, 9546–9549 (1999).

Figure 1
Photo-Bioelectrochemistry of Cyanobacteria Lacking Respiratory Terminal Oxidases
Authors: Suganthan Baviththira , Sekar Narendran , Ramasamy Ramaraja P.
Published: February 2020

In cyanobacteria, the excess electrons produced through photosynthetic electron transport chain at light intensities, are re-oxidized by respiratory terminal oxidases (RTOs) present in the respiratory electron transport chain providing an overflow pathway for excess electrons to minimize photo damage [1]. We have previously demonstrated enhanced photo-bioelectrochemical activity by Synechococcus elongatus if the organism was genetically modified to express an outer membrane cytochrome namely OmcS [2]. We hypothesize that by knocking out the genes corresponding to the RTOs in the genetically engineered Synechococcus elongatus PCC7942 with outer membrane cytochrome (OmcS), the organism’s extracellular electron transfer ability towards the electrode could be further enhanced through the blockage of the overflow pathways. In this study, the genes responsible for the various RTOs in PCC7942 include bd-type quinol oxidase encoded by cydBA (cyd), aa3-type cytochrome oxidase encoded by coxBAC (cox) and cbb3-type cytochrome oxidase encoded by ccoNQ (cco) were knocked out and the resulting mutants were evaluated for their extracellular electron transfer ability through both chemical and electrochemical tests. PCR was carried out to confirm the successful construction of single mutants. Further, double and triple mutants of Synechococcus elongatus PCC7942 in different combinations of the RTO knockouts were also performed and the resulting electrochemical performance was measured using conventional electrochemical techniques.

References:

J. Lea Smith, N. Ross, M. Zori, D.S. Bendall, J.S. Dennis, S.A. Scott, A.G. Smith and C.J. Howe (2013). Thylakoid Terminal oxidases are essential for the Cyanobacterium Synechocystis sp. PCC 6803 to survive rapidly changing light intensities. Plant Physiology. 162. 484- 495.

N. Sekar, R. Jain, Y. Yan, and R.P. Ramasamy (2016). Enhanced Photo-Bio electrochemical energy conversion by genetically engineered Cyanobacteria. Biotechnology and Bioengineering. 113 (3). 675-679

Figure 1
Electron Transfer in Supramolecular Chemistry: Redox-Controlled Dimerization in Electroactive Ureidopyridinones
Authors: Smith Diane K. , Cedano Mario , Darzi Ghazwan M , Clare Laurie A. , Vuong Katrina , Torres Monica
Published: February 2020

An important class of supramolecular systems are those capable of forming dimers held together by multiple linear H-bonds. Of these, the 4 H-bond arrays based on the ureidopyrimidone or UPy unit have found particularly use, having the right combination of ease-of-synthesis and appropriate binding strengths to be useful for the formation of supramolecular polymers and gels. The selling points for these materials are there self-healing properties. By application of heat or mechanical stress the polymer chains will break reversibly at the H-bonds making the material more fluid and allowing a defect to fill in. Upon cooling or relief of the mechanical stress, the H-bonds re-form locking the repair in place. For many applications the use of heat or mechanical stress as the external signal to alter structure is perfect, however, for other applications, a more selective stimulus such as electron transfer would be advantageous. To do this, a reversible redox couple needs to be attached to the UPy in such a way that oxidation or reduction perturbs the H-bond strength. Over the last several years, we have synthesized and investigated the electrochemistry of several such systems, shown below. With UPyH, there is a phenylenediamine redox couple attached to the urea allowing perturbation of the H-donating ability of the urea NH. In the other examples, the redox couple, either a pyridinium [UPy(MeP+)] or a ferrocene [UPy(Fc)], is attached to the pyrimidone ring, allowing perturbation of the H-accepting ability of the pyrimidine N and O. In addition to their potential use in redox-responsive supramolecular materials, these compounds also provide good platforms for fundamental investigations on the role of H-bonding in proton-coupled electron transfer. Indeed, our studies show that with both UPyH and UPy(MeP+) electron transfer leads to proton transfer, resulting in interesting, albeit rather complicated electrochemistry. In both these cases, electron transfer would be expected to increase H-bond strength. In contrast, with UPy(Fc), oxidation should decrease H-bond strength. The result is no proton transfer and greatly simplified electrochemistry, which is more amenable to future supramolecular applications. A thorough analysis of the voltammetry indicates a 107 decrease in Kdim upon oxidation. This result coupled with the high stability of the oxidized form suggests UPy(Fc) is highly amenable to supramolecular applications. Currently we are working on the synthesis of linked UPy(Fc)’s suitable for the formation of supramolecular polymers. Progress on this work will be reported.

Figure 1
Metal- and Oxidant-Free Formal Vinylic C-H/Aromatic C-H Cross Coupling Based on the Stabilized Cation Pool Method
Authors: Yoshida Jun-ichi , Hayashi Ryutaro , Shimizu Akihiro
Published: February 2020

The cation pool method serves as a powerful tool for electroorganic synthesis.1 In the cation pool method organic cations are electrochemically generated and accumulated in solution at low temperatures. Reactions with subsequently added nucleophiles give the desired products. However, the cation pool method cannot be applied to highly unstable cations that decompose during the course of the electrolysis. To expand the scope of the cation pool method, we have developed the stabilized cation pool method, in which electrochemically generated organic cations are stabilized by suitable stabilizing agents and are accumulated in solution. The reactions of the stabilized organic cations with subsequently added nucleophiles give the desired products. We have already reported that the method is successfully applied to benzylic C−H/ aromatic C−H cross-coupling.2

In this paper we show that vinyl C−H/ aromatic C−H cross-coupling can be achieved. I-O-S+R2 generated by oxidation of I2 in the presence of O=SR2
3 adds to ArCH=CH2 to generate and accumulate the corresponding α-(iodomethyl)beznylaminosulfonium ions as stabilized benzyl cations. In the next step, the (α-iodomethyl)beznylaminosulfonium ions are reacted with subsequently added electron-rich aromatic compounds (Ar’H) as nucleophiles. The elimination of HI with a base gives ArAr’C=CH2 to achieve metal- and oxidant-free formal vinylic C-H/aromatic C-H cross coupling.

Yoshida, J.; Ashikari, Y.; Matsumoto, K.; Nokami, T. J. Synth. Org. Chem., Jpn.
2013, 1136.

Hayashi, R.; Shimizu, A.; Yoshida, J. J. Am. Chem. Soc.
2016, 138, 8400.

Ashikari, Y.; Shimizu, A.; Nokami, T.; Yoshida, J. J. Am. Chem. Soc.
2013, 135, 16070.
Electrodeposition and Photocharacterization of In2Se3 Thin Films Using PP-ALD for Use As a Potential Photoanode
Authors: Sisk Peter , Czerniawski Justin , Stickney John Lewellen
Published: February 2020

Indium (III) selenide is an n-type semiconductor that displays 4 main crystal structures. While the more prevalent α and β structures have a direct bandgap of 1.62 eV, the γ structure has been found to have a bandgap of 1.9 eV.1,2 In current work, In2Se3 films were deposited using a pulse potential atomic layer deposition (PP-ALD) technique derived from E-ALD that relies upon the principles of ALD and underpotential deposition (UPD) to create ordered atomic layers. In PP-ALD both precursors, In and Se, are present in one solution that is pumped through the flow cell introducing the ions to the substrate. A cathodic pulse is then used to reductively deposit limited amounts of In and Se on the substrate surface, followed by an anodic pulse used to oxidatively strip any bulk In away from the surface leaving atomic layers of In2Se3. At pH=1, the deposition process creates bubbles in the flow cell that lead to regions of limited deposition. However, at pH=2, less bubbles are formed during the deposition process, leading to more uniform samples. Further investigations into the optimal cathodic and anodic deposition potentials for the PP-ALD program at pH=2 need to be done. These In2Se3 films have been demonstrated to have good photocurrent and have potential as an n-type photoanode in photoelectrochemical cell applications.

Czerniawski, J.; Stickney, J.; Electrodeposition of In2Se3 Using Potential Pulse Atomic Layer Deposition. J. Phys. Chem. C
2016. 120, 16162-16167.

Chang, K.; Lahn, S.; Chang, J. Growth of single-phase In2Se3 by using metal organic vapor deposition with dual-source precursors. Appl. Phys. Lett.
2006. 89, 182118.
Mechanistic Insights into Furfural Reduction on Transition Metals Electrodes from First-Principles Methods
Authors: Shan Nannan , Hanchett Marry K. , Liu Bin
Published: February 2020

Furfural is a significant platform compound derived from biomass. Electrocatalytic reduction of furfural on transition metals emerges as a sustainable approach compared to heterogeneous catalysis to obtain valuable chemicals and fuels, such as furfuryl alcohol (FA) and 2-methylfuran (MF). Although the product selectivity was shown to be strongly depended on the intrinsic properties of the transition metal electrodes, similar as CO2 reduction, the complex chemical nature of furfural presents challenges to investigate the reaction mechanisms, which are still under debate.

Density functional theory (DFT) calculations have been performed for electrocatalytic reduction of furfural to FA and MF on the close-packed (111) and stepped (211) surfaces of Cu, Ag, Pb, and Ni electrodes. The elementary reaction steps have been evaluated based on computational hydrogen electrode (CHE) model. A novel Brønsted–Evans–Polanyi (BEP) relationship has been established for C-O bond cleavage which is necessary for MF production. On Cu, Ag, Pb, and Ni, at both terrace and stepped sites, the first hydrogenation step of C=O, leading to mh6 or mh7 formation, influences the overall reaction activity and product selectivity. It has been found that the pathway via mh6 is more competitive than that via mh7 for FA formation on Cu, Ag, and Pb, whereas on Ni, both mh6 and mh7 routes are competitive due to strong interactions between the furan ring and the substrate. The C-O bond cleavages of furfural, the partially hydrogenated intermediates (mh6 and mh7) and FA were considered as the parallel pathways to produce MF besides FA formation pathways. It is well-known that solvation can facilitate the hydrogenation reactions involving proton-electron pairs. In this work, solvation was confirmed to decrease the C-O bond cleavage energy barriers, which could boost MF production and potentially tune the product selectivity on transition metal electrodes.
Extracting Kinetic Information from Bipolar Electrochemistry
Authors: Anand Robbyn K. , Rahn Kira L. , Knoche Krysti L. , Borchers Janis S. , Riusech Olga L.
Published: February 2020

Bipolar electrodes (BPEs) hold enormous promise for rapid screening of electrocatalysts owing to their ability to be operated wirelessly – without direct ohmic contact to a power source – and in parallel. A BPE is a conductor, immersed in an ionically conducting phase, that facilitates coupled oxidation and reduction reactions at opposing ends when exposed to an electric field. The current arising from these coupled processes can be monitored if one of the reactions leads to a visible change, such as chemiluminescence or anodic stripping of a metal film. Therefore, an array of BPEs operated with a single pair of driving electrodes can facilitate many electrochemical measurements simultaneously. Several reports have clearly demonstrated the utility of BPEs to obtain relative catalytic activity. However, to date, the extraction of specific activity and kinetic rate constants from these measurements remains challenging. We discuss here the experimental factors that contribute to this challenge and we present initial results demonstrating alternative approaches to extract this valuable information from BPE-based screens.
Identification and Characterization of Metal-Oxide Powders with Energy-Resolved Density of Electron Traps Measured By Reversed Double-Beam Photoacoustic Spectroscopy
Authors: Ohtani Bunsho , Nitta Akio , Takase Mai , Takashima Mai
Published: February 2020

Although organic compounds are practically identified by their elemental compositions and nuclear magnetic resonance (NMR) patterns, metal-oxide powders cannot be identified by bulk composition and crystalline structure. Such a difference between molecules and powders is attributable to existence of both surface and bulk for metal-oxide powders. What has been conventionally evaluated as structural properties of metal-oxide powders is crystal phase, primary particle diameter, secondary particle diameter and specific surface area, but those properties reflect only bulk composition or size. In other words, a lack of sufficient analytical method that enables measurement of a property reflecting surface structure has prevented characterization and thereby identification of metal-oxide powders. In this study, we focus on energy-resolved density of electron traps (ERDT) located mainly on the surface of metal-oxide powders, and evaluate ERDT in various particulate samples as a function of energy from valence-band top (VBT) by reversed double-beam photoacoustic spectroscopy (RDB-PAS), in which photoabsorption of trapped electrons directly excited from valence band to electron traps by scanned continuous light is measured by PAS [1].

Representative ERDT patterns of titania powders are shown in Fig. 1. Conduction-band bottom (CBB) depending on the crystalline phase and total density of electron traps increasing with increase in the specific surface area indicate that CBB and total density of electron traps can reflect bulk composition and bulk size, respectively. On the other hand, ERDT patterns of TIO-1 and TIO-13 seem to be clearly different. This result indicates that ERDT can reflect surface structural property. By calculating degree of coincidence z, multiplied by each degree of coincidence for ERDT pattern matching, total density of electron traps and CBB position, some given pairs of two samples which are made by the same manufacturing method show higher z values than those of other pairs. Therefore, it is suggested that an ERDT/CBB pattern can be a fingerprint for metal-oxide powders. Evaluation of VBT by observing ERDT of mixture sample is also discussed.

Fig. 1 Representative ERDT/CBB patterns as energy function from VBT for titania powders.

[1] A. Nitta, M. Takase, M. Takashima, N. Murakami, B. Ohtani, Chem. Commun., 52, 12096-12099 (2016).

Figure 1
(Keynote) Past, Present and Future of Electrochemistry
Authors: Lopes Pietro Papa , Strmcnik Dusan , Stamenkovic Vojislav , Markovic Nenad M
Published: February 2020

Developing and deploying renewable energy technologies will require the application of knowledge, concepts, and tools from a variety of fields including chemistry, materials science, physics and, in particular, electrochemistry. Electrochemistry is, in the broadest sense, the study of relationships between the transformation of electrical energy in chemical bonds and, in the reverse process, the energy stored in chemical bonds back to electrons that can power electrochemical energy storage and conversion systems Central to this presentation will be to introduce - at atomic and molecular levels - electrochemical interfaces in aqueous and organic environments and to argue that we are witnessing the renaissance of electrochemistry. Key correlations will be discussed, including structure-function relationships, functional links between covalent and non-covalent interactions, the role of pH values, and key descriptors that control functional links between activity, stability, sensitivity and conductivity of the interface. Fundamental understanding of critical electrochemical processes at interfaces will provide ample opportunities (and challenges) to further improve the current landscape of sustainable energy production and utilization. We will conclude by asking us what we don’t know but we would like to know about electrochemical interfaces.
(Invited) MEA Studies of Transition Metal Nitride Core-Pt Shell Materials for Fuel Cell Applications
Authors: Cai Yun , Sasaki Kotaro , Kongkanand Anusorn , Adzic Radoslav R.
Published: February 2020

Since the first report of Pt monolayer core-shell catalysts by Adzic’s group(1), attractive owing to both their high Pt utilization and ECSAs, numerous efforts have been devoted to the development of these electrocatalysts for fuel cell applications(2-6). Although many varieties of core-shell catalysts have demonstrated improved activity and durability under RDE conditions, reports on the MEA-level tests are still limited(4). Moreover, since a majority of the reported core materials include significant precious metals (e.g. Pd, Au, etc.), the overall cost of the catalysts remains an ongoing concern. Further, the stability of non-precious metal components (Ni, Co, etc.) in the core still presents severe challenges precluding widespread adoption. To address these concerns, various efforts has been devoted to develop durable electrocatalysts with low or non-PGM cores. Nitridation of the core materials is one promising approach to realizing low cost, durable catalysts. Transition metal nitride cores have exhibited enhanced durability for the oxygen reduction reaction at the RDE level(6, 7). Here we report the development of metal nitrides as catalyst cores or support materials and their performance in fuel cell MEAs. Initial results show durability improvements coupled with higher retentions of Pt mass activities and electrochemical surface areas. These results indicate that Pt monolayer catalysts with metal nitride cores or supports are potential candidates for next-generation fuel cell electrocatalysts.

Reference

R. Adzic, J. Zhang, K. Sasaki, M. Vukmirovic, M. Shao, J. Wang, A. Nilekar, M. Mavrikakis, J. Valerio and F. Uribe, Top. Catal., 46, 249 (2007).

H. Yang, Angew. Chem., Int. Ed., 50, (2011).

C. Koenigsmann, A. C. Santulli, K. Gong, M. B. Vukmirovic, W.-p. Zhou, E. Sutter, S. S. Wong and R. R. Adzic, J. Am. Chem. Soc., 133, (2011).

K. Sasaki, H. Naohara, Y. Choi, Y. Cai, W.-F. Chen, P. Liu and R. R. Adzic, Nat Commun, 3, (2012).

K. A. Kuttiyiel, K. Sasaki, Y. Choi, D. Su, P. Liu and R. R. Adzic, Nano Lett., 12, (2012).

X. Tian, J. Luo, H. Nan, H. Zou, R. Chen, T. Shu, X. Li, Y. Li, H. Song, S. Liao and R. R. Adzic, J. Am. Chem. Soc., 138, (2016).

K. A. Kuttiyiel, Y. Choi, S.-M. Hwang, G.-G. Park, T.-H. Yang, D. Su, K. Sasaki, P. Liu and R. R. Adzic, Nano Energy, 13, (2015).
(Invited) Metal Oxide Nanocoating As Electrocatalyst Support, and More
Authors: Xing Yangchuan
Published: February 2020

With a standard electrochemical oxidation potential at 0.207 V, carbon is prone to being oxidized in PEM fuel cells. This has been observed over the years and addressed by using system controls in fuel cell vehicles. While adding a control system can resolve the problem, it also adds more weight and cost to fuel cell vehicles. Electrochemical corrosion of carbon can be a serious problem in many other kinetically accelerated processes, for example, rechargeable batteries and pseudocapacitors. Certain metal oxides have been studied as possible replacements for carbon. In this talk, I will present our studies on preparing high surface area metal oxides in the form of nanocoatings. In particular, a newly developed technique to make titania and niobia nanocoatings on different carbons, including carbon black and carbon nanotubes, will be presented. To make the oxides electrically conductive, carbon activation and elemental doping were shown to be effective. Furthermore, electronic interactions of metal catalyst nanoparticles and metal oxides will be discussed in terms of promotion of electrocatalytic activity.
(Invited) Tracking Ionic Transport and Electrochemical Reactions in Low-Dimensional Nanomaterialsfor Energy Storage
Authors: Zhu Yimei
Published: February 2020

Lithium-ion batteries are one of the most popular rechargeable energy storage devices for portable electronics and electrical vehicles. To design safe, high-energy electrodes with long-cycle life, we need a better understanding of how electrode materials function in real-time at nanoscale. In this presentation, I will show a method we developed for performing in-situ electron microscopy and spectroscopy to track lithium transport and electrochemical reactions. Three examples will be given. One is on lithium conversion reaction in individual iron fluoride nanoparticles and the other is on lithium intercalation reaction in spinel titanate nanoplatelets. The third one is on lithium diffusion in doped hollandite nanorods which exhibit intriguing 1D tunnel structure that can be manipulated for charge transfer. The microscopy investigations were integrated with bulk x-ray and electrochemical measurements as well as theoretical calculations at atomic scale based on DFT and meso scale based on phase-field theory. The kinetics of ionic transport and the role of defects in the lithiation process will be discussed.

The author would like to thank F. Wang, L. Wu, W. Zhang, F. Xu, Q. Meng, M. Hybertsen, AC. Marschilok and ES. Takeuchi for their collaborations. The work was supported by the U.S. DOE/BES under contract DE-SC0012704.
Bioelectrode Engineering - Control of Catalytic Film Thickness for Enzymatic Fuel Cells
Authors: Li Huaiguang , Buesen Darren , Williams Rhodri , Henig Joerg , Stapf Stefanie , Winkler Martin , Happe Thomas , Plumeré Nicolas
Published: February 2020

Redox hydrogel films are commonly applied for bioelectrode fabrication and we recently demonstrated that such matrices can be engineered to efficiently protect the hydrogenases from O2 damage to enable their integration into H2/O2 biofuel cells [1,2]. The formation of these films is highly reproducible for thicknesses between 30 to 300 µm. However, the most relevant thickness range for technological applications is in the low micrometer thicknesses which are more challenging to produce due to film thickness heterogeneities. Here, we propose the in-situ gelation of monodispersed viologen-modified macromolecules to achieve homogeneous films with thicknesses down to 100 nm. The relative standard deviations of the mean film thickness, was found to be only 4.8%. Electroanalytical investigations reveal defect-free, efficient electron transfer pathways over the complete film. We illustrate the advantage of this method and the importance of the film homogeneity for bioelectrocatalytic applications by investigating the behavior of bioanodes built from ferredoxin-NADP+-oxidoreductase or NiFe-hydrogenase for NADPH and H2 oxidation, respectively. The ability of forming thin films reveal that peak catalytic performances are reached at 10-fold lower catalyst loading compared to conventional approaches owing to the extreme homogeneity in film morphologies. This method will be generally transposable to other related applications, involving catalyst deposition by drop-casting with strict demands for film homogeneity.

[1] N. Plumeré, O. Rüdiger, A. Alsheikh Oughli, R. Williams, J. Vivekananthan, S. Pöller, W. Schuhmann, W. Lubitz, Nature Chemistry, 2014, 6, 822–827.

[2] V. Fourmond, S. Stapf, H. Li, D. Buesen, J. Birrell, O. Rüdiger, W. Lubitz, W. Schuhmann, N. Plumeré, C. Léger, J. Am.
Chem. Soc., 2015, 137, 5494-5505.

Financial support by the Cluster of Excellence RESOLV (EXC 1069) and by the ERC Starting grant REDOX SHIELDS is gratefully acknowledged.
Field Demonstration of Potentiostatically Enriched Microbial Fuel Cell Wastewater Treatment System
Authors: Mohamed Abdelrhman , Zmuda Hannah M. , Coats Erik R. , Beyenal Haluk
Published: February 2020

The ability of microbial communities to exchange electrons with inert electrodes has fueled decades of scientific curiosity and laboratory investigations. Numerous studies have focused on developing applications of bioelectrochemical systems for energy generation, chemical synthesis, and sensor design. In particular, microbial fuel cells (MFCs) have been proposed as a promising technology for energy recovery from organic sources, including domestic and industrial wastewater. Many studies demonstrated the utility of microbial fuel cells in the treatment of wastewater in various reactor sizes from milliliter to cubic meter scale. In order to develop MFCs to be a viable technology for commercial applications, researchers aimed to optimize MFC operation, including optimizing MFC design, electrode materials and geometry, microbial community enrichment, startup and power harvesting strategies.

Most studies have reported startup strategies that includes connecting MFCs to a load, including resistors, capacitors, and power management systems. In this study, we demonstrate an active MFC startup strategy by controlling the potential of both the anode and cathode during the initial microbial community enrichment. The anode and cathode potentials are controlled using a custom dual potentiostat relative to a common Ag/AgCl reference electrode, with a common auxiliary electrode as a current sink/source.

Active MFC startup strategy is demonstrated in a large scale reactor (1200 liter) treating domestic wastewater. Sixteen MFCs (16 anodes and 16 cathodes) are enriched, each using an independent dual potentiostat. Each anode and cathode is a 30 cm x 30 cm carbon fabric electrode, and the counter electrode is a 30 cm x 30 cm x 1 cm graphite felt electrode. Dual potentiostats are connected to a computer using a data acquisition system to record anodic and cathodic current during enrichment. After reaching steady state current, each MFC is connected to a power management system that stores the harvested energy in a supercapacitor. The supercapacitors are discharged intermittently to power small air pumps used to aerate the cathodes.