Regeneration of strong-base anion-exchange resins by sequential chemical displacement

DOEpatents

Brown, Gilbert M.; Gu, Baohua; Moyer, Bruce A.; Bonnesen, Peter V.

2002-01-01

A method for regenerating strong-base anion exchange resins utilizing a sequential chemical displacement technique with new regenerant formulation. The new first regenerant solution is composed of a mixture of ferric chloride, a water-miscible organic solvent, hydrochloric acid, and water in which tetrachloroferrate anion is formed and used to displace the target anions on the resin. The second regenerant is composed of a dilute hydrochloric acid and is used to decompose tetrachloroferrate and elute ferric ions, thereby regenerating the resin. Alternative chemical displacement methods include: (1) displacement of target anions with fluoroborate followed by nitrate or salicylate and (2) displacement of target anions with salicylate followed by dilute hydrochloric acid. The methodology offers an improved regeneration efficiency, recovery, and waste minimization over the conventional displacement technique using sodium chloride (or a brine) or alkali metal hydroxide.

Polyfluorinated boron cluster based salts: A new electrolyte for application in nonaqueous asymmetric AC/Li 4Ti 5O 12 supercapacitors

NASA Astrophysics Data System (ADS)

Ionica-Bousquet, C. M.; Muñoz-Rojas, D.; Casteel, W. J.; Pearlstein, R. M.; Kumar, G. Girish; Pez, G. P.; Palacín, M. R.

Solutions of novel fluorinated lithium dodecaborate (Li 2B 12F xH 12- x) salts have been evaluated as electrolytes in nonaqueous asymmetric supercapacitors with Li 4Ti 5O 12 as negative electrode, and activated carbon (AC) as positive electrode. The results obtained with these new electrolytes were compared with those obtained with cells built using standard 1 M LiPF 6 dissolved in ethylene carbonate and dimethyl carbonate (EC:DMC; 1:1, v/v) as electrolyte. The specific energy, rate capability, and cycling performances of nonaqueous asymmetric cells based on these new electrolyte salts were studied. Cells assembled using the new fluoroborate salts show excellent reversibility, coulombic efficiency, rate capability and improved cyclability when compared with the standard electrolyte. These features confirm the suitability of lithium-fluoro-borate based salts to be used in nonaqueous asymmetric supercapacitors.

[The occurrence of Fusarium varieties and their mycotoxins on silo corn. 1. A method for the determination of zearalenone in corn and corn silage by high performance liquid chromatography (HPLC) with fluorescence detection].

PubMed

Lepom, P

1988-09-01

A method for the determination of zearalenone in maize and maize silage was developed which distinguishes itself by the effective and fast cleaning of the extracts with the help of a silica gel minicolumn. The samples were extracted with chloroform/methanol (9 + 1) and cleaned on a silica gel minicolumn after acid-base partition. The zearalenone was quantitatively determined optionally by means of high-performance liquid chromatography (HPLC) with fluorescence detection (excitation wavelength 236 nm, emission filter 418 nm) or thin-layer chromatography (TLC), p-methoxybenzene diazonium fluoroborate and aluminium chloride were used as detection chemicals. The limits of detection are 0.01 mg/kg (HPLC) and 0.1 mg/kg resp. (TLC), the average recovery is 81%. The method was used for the determination of zearalenone in grain maize, CCM silage and silage from whole maize plants.

4,6-Diaryl/heteroarylpyrimidin-2(1H)-ones as a new class of xanthine oxidase inhibitors.

PubMed

Shukla, Shiwani; Kumar, Dinesh; Ojha, Ritu; Gupta, Manish K; Nepali, Kunal; Bedi, Preet M S

2014-07-01

A series of 4,6-diaryl/heteroarylpyrimidones was synthesized employing silica-supported fluoroboric acid under solvent-free conditions in a microwave reactor. The catalytic influence of HBF4-SiO2 was investigated in detail to optimize the reaction conditions. The synthesized compounds were evaluated for in vitro xanthine oxidase (XO) inhibitory activity for the first time. Structure-activity relationship analyses are also presented. Among the synthesized compounds, VA-5, -9, -10, -12, -22, -23, and -25 were the active inhibitors with IC50 values ranging from 6.45 to 13.46 µM. Compound VA-25 with a pyridinyl ring as ring A and a thiophenyl ring as ring B emerged as the most potent XO inhibitor (IC50 = 6.45 µM) in comparison to allopurinol (IC50 = 12.24 µM). Some of the important interactions of VA-25 with the amino acid residues of the active site of XO were figured out by molecular modeling studies. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Leaching Studies for Copper and Solder Alloy Recovery from Shredded Particles of Waste Printed Circuit Boards

NASA Astrophysics Data System (ADS)

Kavousi, Maryam; Sattari, Anahita; Alamdari, Eskandar Keshavarz; Fatmehsari, Davoud Haghshenas

2018-03-01

Printed circuit boards (PCBs) comprise various metals such as Cu, Sn, and Pb, as well as platinum group metals. The recovery of metals from PCBs is important not only due to the waste treatment but also for recycling of valuable metals. In the present work, the leaching process of Cu, Sn, and Pb from PCBs was studied using fluoroboric acid and hydrogen peroxide as the leaching agent and oxidant, respectively. Pertinent factors including concentration of acid, temperature, liquid-solid ratio, and concentration of oxidizing agent were evaluated. The results showed 99 pct of copper and 90 pct solder alloy were dissolved at a temperature of 298 K (25 °C) for 180 minutes using 0.6 M HBF4 for the particle size range of 0.15 to 0.4 mm. Moreover, solid/liquid ratio had insignificant effect on the recovery of metals. Kinetics analysis revealed that the chemical control regime governs the process with activation energy 41.25 and 38.9 kJ/mol for copper and lead leaching reactions, respectively.

Leaching Studies for Copper and Solder Alloy Recovery from Shredded Particles of Waste Printed Circuit Boards

NASA Astrophysics Data System (ADS)

Kavousi, Maryam; Sattari, Anahita; Alamdari, Eskandar Keshavarz; Fatmehsari, Davoud Haghshenas

2018-06-01

Printed circuit boards (PCBs) comprise various metals such as Cu, Sn, and Pb, as well as platinum group metals. The recovery of metals from PCBs is important not only due to the waste treatment but also for recycling of valuable metals. In the present work, the leaching process of Cu, Sn, and Pb from PCBs was studied using fluoroboric acid and hydrogen peroxide as the leaching agent and oxidant, respectively. Pertinent factors including concentration of acid, temperature, liquid-solid ratio, and concentration of oxidizing agent were evaluated. The results showed 99 pct of copper and 90 pct solder alloy were dissolved at a temperature of 298 K (25 °C) for 180 minutes using 0.6 M HBF4 for the particle size range of 0.15 to 0.4 mm. Moreover, solid/liquid ratio had insignificant effect on the recovery of metals. Kinetics analysis revealed that the chemical control regime governs the process with activation energy 41.25 and 38.9 kJ/mol for copper and lead leaching reactions, respectively.

Taking Up the Cyanine Challenge with Quantum Tools

PubMed Central

2015-01-01

Conspectus Cyanine derivatives, named from the Greek word kyanos meaning dark-blue, were discovered more than 150 years ago and remain one of the most widely used classes of organic dyes with contemporary applications in photography (panchromatic emulsions), information storage (CD-R and DVD-R media) and biochemistry (DNA and protein labeling) fields. Cyanine chromogens consist of a charged π-conjugated segment containing an odd number of sp2 carbon atoms with the chain capped at the extremities by two electronegative centers, typically nitrogen or oxygen atoms. Cyanines are characterized by a vanishing bond length alternation indicating nearly equal carbon–carbon bond lengths, as well as a very intense and sharp absorption band presenting a shoulder. This hallmark band undergoes a strong red shift when the chain is extended. This so-called vinyl shift is extremely large (ca. 100 nm for each pair of carbon atoms added in the π-conjugated path), making cyanines ideal building blocks for the design of devices with near-infrared applications. Numerous cyanines also exhibit emission bands with large quantum yields. These exceptional optical properties explain why both canonical cyanines and the corresponding fluoroborates (e.g., boron-dipyrromethene, BODIPY) remain the focus of an ever-growing body of experimental work. In turn, this popularity has stimulated quantum mechanical investigations aiming, on the one hand, at probing the specific electronic nature of cyanine dyes and, on the other hand, at helping to design new dyes. However, the adiabatic approximation to time-dependent density functional theory, the most widespread ab initio model for electronically excited states, fails to accurately reproduce the absorption spectra of cyanine derivatives: it yields a systematic and large underestimation of the experimental wavelengths irrespective of the details of the computational protocol. In contrast, highly correlated wave function approaches provide accurate transition energies for model systems but are hardly applicable to real-life cyanines and BODIPY. This indicates that setting up a computationally tractable theoretical protocol that provides both robust and accurate optical spectra for cyanine-based dyes is a major challenge that has only been taken up lately. In this Account, we compile the most recent advances in the field by considering both compact streptocyanines and large fluoroborates. For the former, we summarize the key results obtained with a large panel of theoretical approaches, allowing us not only to understand the origin of the cyanine challenge but also to pinpoint the schemes presenting the most promising accuracy/effort ratio. For the latter, we show via selected examples how theoretical models can be used to reproduce simultaneously experimental band shapes and transition energies, thus paving the way to an efficient in silico design of new compounds. PMID:25710687

Selective separation of copper over solder alloy from waste printed circuit boards leach solution.

PubMed

Kavousi, Maryam; Sattari, Anahita; Alamdari, Eskandar Keshavarz; Firozi, Sadegh

2017-02-01

The printed circuit boards (PCBs) from electronic waste are important resource, since the PCBs contain precious metals such as gold, copper, tin, silver, platinum and so forth. In addition to the economic point of view, the presence of lead turns this scrap into dangerous to environment. This study was conducted as part of the development of a novel process for selective recovery of copper over tin and lead from printed circuit boards by HBF 4 leaching. In previous study, Copper with solder alloy was associated, simultaneously were leached in HBF 4 solution using hydrogen peroxide as an oxidant at room temperature. The objective of this study is the separation of copper from tin and lead from Fluoroborate media using CP-150 as an extractant. The influence of organic solvent's concentration, pH, temperature and A/O phase ratio was investigated. The possible extraction mechanism and the composition of the extracted species have been determined. The separation factors for these metals using this agent are reported, while efficient methods for separation of Cu (II) from other metal ions are proposed. The treatment of leach liquor for solvent extraction of copper with CP-150 revealed that 20% CP-150 in kerosene, a 30min period of contact time, and a pH of 3 were sufficient for the extraction of Cu(II) and 99.99% copper was recovered from the leached solution. Copyright © 2016. Published by Elsevier Ltd.

Tuning the Composition of Electrodeposited Bimetallic Tin-Lead Catalysts for Enhanced Activity and Durability in Carbon Dioxide Electroreduction to Formate.

PubMed

Moore, Colin E; Gyenge, Előd L

2017-09-11

Bimetallic Sn-Pb catalysts with five different Sn/Pb atomic ratios were electrodeposited on Teflonated carbon paper and non-Teflonated carbon cloth using both fluoroborate- and oxide-containing deposition media to produce catalysts for the electrochemical reduction of CO 2 (ERC) to formate (HCOO - ). The interaction between catalyst composition, morphology, substrate, and deposition media was investigated by using cyclic voltammetry and constant potential electrolysis at -2.0 V versus Ag/AgCl for 2 h in 0.5 m KHCO 3 . The catalysts were analyzed before and after electrolysis by using SEM and XRD to determine the mechanisms of Faradaic efficiency loss and degradation. Catalysts that are mainly Sn with 15-35 at % Pb generated Faradaic efficiencies up to 95 % with a stable performance. However, pure Sn catalysts showed high initial stage formate production rates but experienced an extensive (up to 30 %) decrease of the Faradaic efficiency. The XRD results demonstrated the presence of polycrystalline SnO 2 after electrolysis using Sn-Pb catalysts with 35 at % Pb and its absence in the case of pure Sn. It is proposed that the presence of Pb (15-35 at %) in mainly Sn catalysts stabilized SnO 2 , which is responsible for the enhanced Faradaic efficiency and catalytic durability in the ERC. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ammonium boranes for the selective complexation of cyanide or fluoride ions in water.

PubMed

Hudnall, Todd W; Gabbaï, François P

2007-10-03

With the recognition of aqueous fluoride and cyanide ions as an objective, we have investigated the anion binding properties of two isomeric ammonium boranes, namely [p-(Mes2B)C6H4(NMe3)]+ ([1]+) and [o-(Mes2B)C6H4(NMe3)]+ ([2]+). These cationic boranes, which could be obtained by reaction of the known 4- and 2-dimesitylboryl-N,N-dimethylaniline with MeOTf, have been investigated both experimentally and computationally. They both react with fluoride and cyanide ions in organic solvents to afford the corresponding fluoroborate/ or cyanoborate/ammonium zwitterions 1F, 1CN, 2F, and 2CN. In aqueous solution, however, these cationic boranes behave as remarkably selective receptors. Indeed, [1]+ only complexes cyanide ions while [2]+ only complexes fluoride ions. In H2O/DMSO 60:40 vol (HEPES 6 mM, pH 7), the cyanide binding constant of [1]+ and the fluoride binding constant of [2]+ are respectively equal to 3.9 (+/-0.1) x 108 and 910 (+/-50) M-1. Structural and computational studies indicate that both steric and electronic effects contribute to the unusual selectivity displayed by these cationic boranes. Owing to favorable Coulombic effects, the para-derivative [1]+ has a very high affinity for cyanide; yet these effects are not sufficiently intense to allow complexation of the more efficiently hydrated and less basic fluoride anion. In the case of the ortho-derivative [2]+, the proximity of the ammonium moiety leads to an increase in the Lewis acidity of the boron center thus making fluoride binding possible. However, steric effects prevent cyanide coordination to the boron center of [2]+. Finally, cation [1]+ and [2]+ bind their dedicated anions reversibly and show a negligible response in the presence of other common anions including Cl-, Br-, I-, NO3-, OAc-, H2PO4-, and HSO4-.

Mechanism of dissolution of a lithium salt in an electrolytic solvent in a lithium ion secondary battery: a direct ab initio molecular dynamics (AIMD) study.

PubMed

Tachikawa, Hiroto

2014-06-06

The mechanism of dissolution of the Li(+) ion in an electrolytic solvent is investigated by the direct ab initio molecular dynamics (AIMD) method. Lithium fluoroborate (Li(+)BF4(-)) and ethylene carbonate (EC) are examined as the origin of the Li(+) ion and the solvent molecule, respectively. This salt is widely utilized as the electrolyte in the lithium ion secondary battery. The binding of EC to the Li(+) moiety of the Li(+)BF4(-) salt is exothermic, and the binding energies at the CAM-B3LYP/6-311++G(d,p) level for n=1, 2, 3, and 4, where n is the number of EC molecules binding to the Li(+) ion, (EC)n(Li(+)BF4(-)), are calculated to be 91.5, 89.8, 87.2, and 84.0 kcal mol(-1) (per EC molecule), respectively. The intermolecular distances between Li(+) and the F atom of BF4(-) are elongated: 1.773 Å (n=0), 1.820 Å (n=1), 1.974 Å (n=2), 1.942 Å (n=3), and 4.156 Å (n=4). The atomic bond populations between Li(+) and the F atom for n=0, 1, 2, 3, and 4 are 0.202, 0.186, 0.150, 0.038, and 0.0, respectively. These results indicate that the interaction of Li(+) with BF4(-) becomes weaker as the number of EC molecules is increased. The direct AIMD calculation for n=4 shows that EC reacts spontaneously with (EC)3(Li(+)BF4(-)) and the Li(+) ion is stripped from the salt. The following substitution reaction takes place: EC+(EC)3(Li(+)BF4(-))→(EC)4Li(+)-(BF4(-)). The reaction mechanism is discussed on the basis of the theoretical results. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantifying the Performances of DFT for Predicting Vibrationally Resolved Optical Spectra: Asymmetric Fluoroborate Dyes as Working Examples.

PubMed

Bednarska, Joanna; Zaleśny, Robert; Bartkowiak, Wojciech; Ośmiałowski, Borys; Medved', Miroslav; Jacquemin, Denis

2017-09-12

This article aims at a quantitative assessment of the performances of a panel of exchange-correlation functionals, including semilocal (BLYP and PBE), global hybrids (B3LYP, PBE0, M06, BHandHLYP, M06-2X, and M06-HF), and range-separated hybrids (CAM-B3LYP, LC-ωPBE, LC-BLYP, ωB97X, and ωB97X-D), in predicting the vibrationally resolved absorption spectra of BF 2 -carrying compounds. To this end, for 19 difluoroborates as examples, we use, as a metric, the vibrational reorganization energy (λ vib ) that can be determined based on the computationally efficient linear coupling model (a.k.a. vertical gradient method). The reference values of λ vib were determined by employing the CC2 method combined with the cc-pVTZ basis set for a representative subset of molecules. To validate the performances of CC2, comparisons with experimental data have been carried out as well. This study shows that the vibrational reorganization energy, involving Huang-Rhys factors and normal-mode frequencies, can indeed be used to quantify the reliability of functionals in the calculations of the vibrational fine structure of absorption bands, i.e., an accurate prediction of the vibrational reorganization energy leads to absorption band shapes better fitting the selected reference. The CAM-B3LYP, M06-2X, ωB97X-D, ωB97X, and BHandHLYP functionals all deliver vibrational reorganization energies with absolute relative errors smaller than 20% compared to CC2, whereas 10% accuracy can be achieved with the first three functionals. Indeed, the set of examined exchange-correlation functionals can be divided into three groups: (i) BLYP, B3LYP, PBE, PBE0, and M06 yield inaccurate band shapes (λ vib,TDDFT < λ vib,CC2 ), (ii) BHandHLYP, CAM-B3LYP, M06-2X, ωB97X, and ωB97X-D provide accurate band shapes (λ vib,TDDFT ≈ λ vib,CC2 ), and (iii) LC-ωPBE, LC-BLYP, and M06-HF deliver rather poor band topologies (λ vib,TDDFT > λ vib,CC2 ). This study also demonstrates that λ vib can be reliably estimated using the CC2 model and the relatively small cc-pVDZ basis set. Therefore, the linear coupling model combined with the CC2/cc-pVDZ level of theory can be used as a very efficient approach to determine λ vib values that can be used to select the most adequate functional for more accurate vibronic calculations, e.g., including more refined models and environmental effects.

Interfacial characteristics of propylene carbonate and validation of simulation models for electrochemical applications

NASA Astrophysics Data System (ADS)

You, Xinli

Supercapacitors have occupy an indispensable role in today's energy storage systems due to their high power density and long life. The introduction of car- bon nanotube (CNT) forests as electrode offers the possibility of nano-scale design and high capacitance. We have performed molecular dynamics simulations on a CNT forest-based electrochemical double-layer capacitor (EDLC) and a widely used electrolyte solution (tetra-ethylammonium tetra-fluoroborate in propylene carbonate, TEABF4 /PC). We compare corresponding primitive model and atomically detailed model of TEABF4 /P, emphasizing the significance of ion clustering in electrolytes. The molecular dynamic simulation results suggests that the arrangement of closest neigh- bors leads to the formation of cation-anion chains or rings. Fuoss's discussion of ion-pairing model provides the approximation for a primitive model of 1-1 electrolyte is not broadly satisfactory for both primitive and atomically detailed cases. A more general Poisson statistical assumption is shown to be satisfactory when coordina- tion numbers are low, as is likely to be the case when ion-pairing initiates. We examined the Poisson-based model over a range of concentrations for both models of TEABF4 /P, and the atomically detailed model results identified solvent-separated nearest-neighbor ion-pairs. Large surface areas plays an essential role in nanomaterial properties, which calls for an accurate description of interfaces through modeling. We studied propylene carbonate, a widely used solvent in EDLC systems. PC wets graphite with a contact angle of 31°. The MD simulation model reproduced this contact angle after reduction 40% of the strength of graphite-C atom Lennard-Jones interactions with the solvent. The critical temperature of PC was accurately evaluated by extrapolating the PC liquid-vapor surface tensions. PC molecules tend to lie flat on the PC liquid-vapor surface, and project the propyl carbon toward the vapor phase. Liquid PC simulations also provide basic data for construction of accurate information to assist in device- level modeling of EDLCs. The most serious uncertainty with previous simulations of CNT based EDLCs was definition of the actual composition of the pores. Therefore, direct simulations of filling of CNT forest based electrochemical double-layer capacitors with TEABF4 /P solution was performed. Those calculation characterize the charging and discharg- ing process, including rates of charging responses, the possibility of bubble forma- tion, and kinetic properties with confinement. The mobilities of ions and solvent was investigated through mean square displacement (MSD) and velocity autocorrela- tion functions (VACF). The memory kernel was extracted from VACF by discretized linear-equation solving and a specialized Fourier transform method, results implies the existence of dielectric friction. With the interest in chemical features of EDLCs, a multi-scale theory was de- veloped to embed high resolution ab initio molecular dynamics (AIMD) methods into studies of EDLCs. This theory was based on McMillan-Mayer theory, potential dis- tribution approach, and quasi-chemical theory. The quasi-chemical theory allow us to break-up the free energies into packing, outer-shell and chemical contributions, where the last part can be done by AIMD directly. For the primitive model of TEABF4 /P, Gaussian statistical models are effective for these outer-shell contributions. And the Gaussian approximation is more efficient than the Bennett method in achieving an accurate mean activity coefficient.

New Class of Flow Batteries for Terrestrial and Aerospace Energy Storage Applications

NASA Technical Reports Server (NTRS)

Bugga, Ratnakumar V.; West, William C.; Kindler, Andrew; Smart, Marshall C.

2013-01-01

Future sustainable energy generation technologies such as photovoltaic and wind farms require advanced energy storage systems on a massive scale to make the alternate (green) energy options practical. The daunting requirements of such large-scale energy systems such as long operating and cycle life, safety, and low cost are not adequately met by state-of-the-art energy storage technologies such as vanadium flow cells, lead-acid, and zinc-bromine batteries. Much attention is being paid to redox batteries specifically to the vanadium redox battery (VRB) due to their simplicity, low cost, and good life characteristics compared to other related battery technologies. NASA is currently seeking high-specific- energy and long-cycle-life rechargeable batteries in the 10-to-100-kW range to support future human exploration missions, such as planetary habitats, human rovers, etc. The flow batteries described above are excellent candidates for these applications, as well as other applications that propose to use regenerative fuel cells. A new flow cell technology is proposed based on coupling two novel electrodes in the form of solvated electron systems (SES) between an alkali (or alkaline earth) metal and poly aromatic hydrocarbons (PAH), separated by an ionically conducting separator. The cell reaction involves the formation of such SES with a PAH of high voltage in the cathode, while the alkali (or alkaline earth metal) is reduced from such an MPAH complex in the anode half-cell. During recharge, the reactions are reversed in both electrodes. In other words, the alkali (alkaline earth) metal ion simply shuttles from one M-PAH complex (SES) to another, which are separated by a metal-ion conducting solid or polymer electrolyte separator. As an example, the concept was demonstrated with Li-naphthalene//Li DDQ (DDQ is 2,3-Dichloro-5,6-dicyano- 1,4-benzoquinone) separated by lithium super ion conductor, either ceramic or polymer (solid polymer or gel polymer) electrolytes. The reactants are Li-naphthalene dissolved in tetrahydrofuran (THF) with a lithium salt of 1M LiBF4 (lithium tetra fluoroborate) in the anode compartment, and DDQ again dissolved in THF and also containing 1M LiBF4 salt in the cathode half-cell. The solid electrolyte separator used in the first set of experiments is a ceramic solid electrolyte, available from a commercial source. The open circuit voltage of the cells is close to 3.0 V, as expected from the individual half-cell voltages of Li-naphthalene and Li-DDQ. Upon discharge, the cell shows steady discharge voltage of 2.7 V, which confirms that the electrochemical processes do involve lithium ion shuttling from the anodic compartment to the cathode half-cell. The reversibility or rechargeability is demonstrated by charging the partially discharged cells (i.e., with lithium present in the DDQ half). Once again, a steady voltage close to 3.0 V was observed during charge, indicating that the system is quite reversible. In the subsequent concept-demonstration studies, the ceramic electrolyte has been replaced with a gel polymer electrolyte, e.g., PVDF-HFP (poly vinylene difluoride hexafluoropropene) gel, which has several advantages such as high ionic conductivity (almost comparable to liquid electrolyte and about 2 orders of magnitude better than the ceramic equivalent), lower cost, and possibly higher chemical stability at the anode. In addition, it can be bonded to the electrode by thermal fusion to form membrane electrode assemblies (MEAs), as is done in fuel cells.