Proton exchange membrane fuel cells performance enhancement using bipolar channel indentation

Mohammad Dehsara,Mohammad J. Kermani 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.1

The influence of bipolar channel indentation on the performance enhancement of proton exchange membrane (PEM) fuel cells is studiedusing three-dimensional computation of a whole single cell. It is assumed that the cell operates under a fixed dry condition of 80°C, 1atm, and inlets’ relative humidity of 10%. Hence the sole influence of channel-bed shapes on the cell performance was considered. Threestraight channels with different bed shapes were considered, namely, flat and indented (including semicircular and wavy) channel-beds. Itis observed that the channel-bed shapes directly influence the fluid mechanics of the flow field within the channels, such as the magnitudeand direction of the velocity vectors, pressure variations along the channels, and the consumption rates of oxygen and hydrogenwithin the catalyst layer. The results reveal that gas flow channel indentations in the anode and cathode sides enhance the net transport ofreacting species through the porous layers toward the catalyst layer. The improvement of the cell due to channel indentation is observedto be in the range 18-22%.

A sulfonated poly(arylene ether sulfone)/polyimide nanofiber composite proton exchange membrane for microbial electrolysis cell application under the coexistence of diverse competitive cations and protons

Park, Sung-Gwan,Chae, Kyu-Jung,Lee, Mooseok Elsevier 2017 Journal of membrane science Vol.540 No.-

<P><B>Abstract</B></P> <P>A sulfonated poly(arylene ether sulfone) (SPAES)/polyimide nanofiber (PIN) composite proton exchange membrane was developed for use in microbial electrolysis cells (MECs), where diverse cations that compete with proton coexist in high concentrations. It was fabricated by impregnating SPAES as a proton-conducting polymer into PIN as a supporter for mechanical reinforcement. The membrane showed excellent mechanical and dimensional stability (tensile strength > 40MPa) due to membrane reinforcement by nanofibers, despite having a high water uptake (35 ± 3%) and ion exchange capacity (2.3 ± 0.3meq/g). This novel membrane was highly selective for protons while excluding other competing cations; thus, it significantly mitigated the proton accumulation problem in the anode when applied to actual MECs. In addition to 1.5-fold greater proton transport, the SPAES/PIN membrane exhibited 3–10-fold less undesirable crossover of other cations depending on the species and 2–2.5-fold less gas permeability compared to Nafion-211 membrane. The application of this membrane improved hydrogen production efficiency of MEC by 32.4% compared to Nafion-211 and better hydrogen purity (90.3% for SPAES/PIN vs. 61.8% for Nafion-211). Therefore, this novel membrane has good potential for MEC applications, especially when protons and other competing cations are present together, due to its superior proton selectivity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A hydrocarbon-based SPAES/PIN composite proton exchange membrane was developed. </LI> <LI> Sulfonated poly(arylene ether sulfone) (SPAES) was used as a proton conductor. </LI> <LI> The SPAES/PIN composite membrane showed excellent mechanical and dimensional stability. </LI> <LI> The novel membrane was highly selective for protons while excluding other competing cations. </LI> <LI> The membrane showed significant improvement over Nafion-211 for microbial electrolysis cell performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

평행류와 Interdigitated 유로를 가진 교분자 전해질 연료전지(PEMFC)의 성능특성에 대한 수치해석

이필형,조선아,최성훈,황상순,Lee, Pil-Hyong,Cho, Son-Ah,Choi, Seong-Hun,Hwang, Sang-Soon 한국전기화학회 2006 한국전기화학회지 Vol.9 No.4

고분자 전해질 연료전지의 분리판의 유동채널 설계는 고전류밀도에서 발생하는 농도분극에 직접적인 영향을 줄 뿐 아니라 생성되는 물의 효과적인 전달을 위하여 매우 중요하다. 평행류 유로와 interdigitated 유로의 성능비교를 위하여 연료극과 공기극이 포함된 완전한 형태의 고분자 전해질 연료전지의 3차원 수치해석모델을 개발하였다. 수치해석모델을 사용하여 평행류 유동장과 interdigitated 유동장의 압력강하, 채널간의 물질전달, $H_2O$와 $O_2$의 농도 분포 그리고 i-V 성능을 비교하였다. 그 결과 물질전달에서 채널간의 대류에 의한 물질전할이 더욱 우수한 interdigitated 유동채널에서 성능이 더 높게 나타났으며 압력강하는 보다 크게 나타나 설계시 두가지 성능에 대한 상호보완이 필요함을 알 수 있었다. Optimum design of flow channel in the separation plate of Proton Exchange Membrane Fuel Cell is very prerequisite to reduce concentration over potential at high current region and remove the water generated in cathode effectively. In this paper, fully 3 dimensional computational model which solves anode and cathode flow fields simultaneously is developed in order to compare the performance of fuel cell with parallel and interdigitated flow channels. Oxygen and water concentration and pressure drop are calculated and i-V performance characteristics are compared between flows with two flow channels. Results show that performance of fuel cell with interdigitated flow channel is hi민or than that with parallel flow channel at high current region because hydrogen and oxygen in interdigitated flow channel are transported to catalyst layer effectively due to strong convective transport through gas diffusion layer but pressure drop is larger than that in parallel flow channel. Therefore Trade-off between power gain and pressure loss should be considered in design of fuel cell with interdigitated flow channel.

Dirac Coupled-channel Analyses of the High-lying Excited States at 22Ne(p,p0)22Ne

Sugie Shim,Moon-Won Kim 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.12

Dirac phenomenological coupled-channel analyses are performed by using an optical potential model for the high-lying excited vibrational states at 800-MeV unpolarized proton inelastic scatterings from 22Ne nucleus. Lorentz-covariant scalar and time-like vector potentials are used as direct optical potentials, and the first-order vibrational collective model is used for the transition optical potentials to describe the high-lying excited vibrational collective states. The complicated Dirac coupled-channel equations are solved phenomenologically by using a sequential iteration method by varying the optical potential and the deformation parameters. Relativistic Dirac coupled-channel calculations are able to describe the high-lying excited states of the vibrational bands in 22Ne clearly better than the nonrelativistic coupled-channel calculations. The channel-coupling effects of the multistep process for the excited states of the vibrational bands are investigated. The deformation parameters obtained from the Dirac phenomenological calculations for the high-lying vibrational excited states in 22Ne are found to agree well with those obtained from the nonrelativistic calculations using the same Woods-Saxon potential shape.

PEM 수전해의 성능 향상을 위한 flow channel 설계

김성근(Seong Keun Kim),문종운(Jong Woon Moon),정성용(Sung Yong Jung) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

PEMWE (proton exchange membrane water electrolyzer) uses a polymer electrolyte membrane as an electrolyte and requires high manufacturing costs because precious metals are used as catalysts. Accordingly, many studies are being conducted to increase the hydrogen production efficiency of PEMWE. A general PEMWE uses a titanium mesh as a PTL (porous transport layer) for a constant current supply. However, the mesh disturbs the water contaction to the electrolyte membrane because the produced gas during the chemical reaction is not smoothly discharged. Therefore, this study compared the performance with various flow channel designs to improve gas reduction and water supply. Three types of flow channels, including serial type, parallel type, and dual-channel type, were designed and compared their performances. Water was supplied at 15 mL/min, 90 °C, and performances were measured with current densities ranging from 0 A/cm² to 0.8 A/cm². At a current density of 0.8 A/cm², the basic type was 3.80 V, the serial type was 3.13 V, the parallel type was 3.39 V and the dual-channel type was 3.27 V. The serial type has the best performance because gas discharge is more active than other flow channels.

Charge transport in graphene oxide

Chang, Dong Wook,Baek, Jong-Beom Elsevier 2017 Nano today Vol.17 No.-

<P><B>Abstract</B></P> <P>The transport of ionic species in nano-fluidic channels has recently attracted tremendous interest in various research areas. This is because extraordinary nanoscale transport phenomena have been achieved in these materials, including ultrafast and highly selective ion movement. A variety of organic and inorganic materials have been employed to construct nano-channels or nano-pores with controlled sizes and dimensions. In particular, because of its unique two-dimensional planar architecture, as well as the possession of numerous oxygenated functionalities, GO has emerged as a promising building block for high-performance nano-fluidic ion channels. The simple exfoliation-reconstruction approach can readily assemble individual GO sheets into a free-standing, layered, film-like structure. In addition to its utilization as a versatile solid support for nano-fluidic ion transport, GO can play different but positive roles as a filler in composite electrolytes, as a mixed proton/electron conductor, and as a selective ion permeation membrane. Herein, we summarize the recent advances in the transport of ionic species within GO-based electrolytes. Moreover, the perspectives and current challenges of this promising field are discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanoscale transport phenomena have been summarized. </LI> <LI> Graphene oxide (GO) has emerged as high-performance nano-fluidic ion channels. </LI> <LI> An exfoliation-reconstruction process is utilized as a versatile method for GO electrolytes. </LI> <LI> GO can play positive roles as a mixed proton/electron conductor. </LI> <LI> In this review, the recent advances and perspectives in GO-based electrolytes are discussed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Current Sensing Atomic Force Microscopy를 이용한 수화현상에 의한 Ionic Channel Network 변화 연구

권오성,이태동,이용욱,김주곤 한국물리학회 2015 새물리 Vol.65 No.4

Proton exchange membranes (PEMs) are being used as gas separators, insulating electrodes, and proton conductors. Thus, understanding the morphological structure of a PEM is one of the important issues for the characterization of a proton exchange membrane fuel cell (PEMFC). Specifically, the variation in the ionic channel network under hydration of a PEM is a crucial issue. In this study, we characterized the variation in the ionic channel network of Nafion 112 under a hydrated condition by using a current-sensing atomic force microscope (CSAFM). We built a mini-sized PEMFC by using the Pt-coated tip of a CSAFM and a PEM coated with Pt/C on one side. The mini-sized PEMFC could detect the local proton conductivity of the ionic clusters in the PEM. We measured the local proton conductivity of ionic clusters by using a mini-sized PEM under different relative humidities. The results were characterized by using the ballistic transport model and revealed several crucial trends, such as increasing proton conductivity and proton mean free path with increasing relative humidity. 이온교환막은 고분자 이온교환막 연료전지의 핵심부품으로써 음극과 양극으로 제공되는 수소와 산소를 분리하며, 음극과 양극을 전기적으로 절연시키며, 또한 연료전지가 양성자 전도도를 가지도록 하는 역할을 수행한다. 이러한 이유로 이온교환막의 구조를 이해하는 것은 연료전지를 분석하는데 있어서 중요한 주제 중의 하나이며 특히, 수화 현상에 의한 이온교환막 내부의 Ionic channel network의 변화를 분석하는 것은 가장 중요한 주제이다. 본 연구에서는 백금이 코팅된 current sensing atomic force microscope의 팁과 한쪽 면에만 전극이 부착 된 Nafion 112 맴브레인을 이용하여 미니 연료전지를 모사하였다. 미니 연료전지를 이용하여 ionic cluster들의 상대습도에 따른 미세한 양성자 전도도 측정하였으며 결과는 ballistic transport model을 이용하여 분석하였다. 그 결과 양성자 전도도는 및 양성자의 mean free path 또한 비선형적으로 증가함을 보였다.

(-)-Epigallocatechin-3-gallate inhibits voltage-gated proton currents in BV2 microglial cells

Jin, S.,Park, M.,Song, J.H. North-Holland ; Elsevier Science Ltd 2013 european journal of pharmacology Vol.698 No.1

(-)-Epigallocatechin-3-gallate (EGCG), the principal constituent of green tea, protects neurons from toxic insults by suppressing the microglial secretion of neurotoxic inflammatory mediators. Voltage-gated proton channels are expressed in microglia, and are required for NADPH oxidase-dependent reactive oxygen species generation. Brain damage after ischemic stroke is dependent on proton channel activity. Accordingly, we examined whether EGCG could inhibit proton channel function in the murine microglial BV2 cells. EGCG potently inhibited proton currents with an IC<SUB>50</SUB> of 3.7μM. Other tea catechins, (-)-epigallocatechin, (-)-epicatechin and (-)-epicatechin-3-gallate, were far less potent than EGCG. EGCG did not change the kinetics of proton currents such as the activation and the deactivation time constants, the reversal potential and the activation voltage, suggesting that the gating process of proton channels were not altered by EGCG. EGCG is known to disturb lipid rafts by sequestering cholesterol. However, neither extraction of cholesterol with methyl-β-cyclodextrin or cholesterol supplementation could reverse the EGCG inhibition of proton currents. In addition, the EGCG effect was preserved in the presence of the cytoskeletal stabilizers paclitaxel and phalloidin, phosphatase inhibitors, the antioxidant Trolox, superoxide dismutase or catalase. The proton channel inhibition can be a substantial mechanism for EGCG to suppress microglial activation and subsequent neurotoxic events.

Antipsychotics, chlorpromazine and haloperidol inhibit voltage-gated proton currents in BV2 microglial cells

Shin, H.,Song, J.H. North-Holland ; Elsevier Science Ltd 2014 european journal of pharmacology Vol.738 No.-

Microglial dysfunction and neuroinflammation are thought to contribute to the pathogenesis of schizophrenia. Some antipsychotic drugs have anti-inflammatory activity and can reduce the secretion of pro-inflammatory cytokines and reactive oxygen species from activated microglial cells. Voltage-gated proton channels on the microglial cells participate in the generation of reactive oxygen species and neuronal toxicity by supporting NADPH oxidase activity. In the present study, we examined the effects of two typical antipsychotics, chlorpromazine and haloperidol, on proton currents in microglial BV2 cells using the whole-cell patch clamp method. Chlorpromazine and haloperidol potently inhibited proton currents with IC<SUB>50</SUB> values of 2.2μM and 8.4μM, respectively. Chlorpromazine and haloperidol are weak bases that can increase the intracellular pH, whereby they reduce the proton gradient and affect channel gating. Although the drugs caused a marginal positive shift of the activation voltage, they did not change the reversal potential. This suggested that proton current inhibition was not due to an alteration of the intracellular pH. Chlorpromazine and haloperidol are strong blockers of dopamine receptors. While dopamine itself did not affect proton currents, it also did not alter proton current inhibition by the two antipsychotics, indicating dopamine receptors are not likely to mediate the proton current inhibition. Given that proton channels are important for the production of reactive oxygen species and possibly pro-inflammatory cytokines, the anti-inflammatory and antipsychotic activities of chlorpromazine and haloperidol may be partly derived from their ability to inhibit microglial proton currents.

Water channel morphology of non-perfluorinated hydrocarbon proton exchange membrane under a low humidifying condition

Park, Chi Hoon,Kim, Tae-Ho,Nam, Sang Yong,Hong, Young Taik Elsevier 2019 International journal of hydrogen energy Vol.44 No.4

<P><B>Abstract</B></P> <P>Water channel formation of non-perfluorinated proton exchange membranes (PEMs) under a low humidifying condition is a very important issue, due to weaker phase separation between hydrophilic and hydrophobic moieties than in the case of perfluorinated PEMs such as Nafion. In this study, we performed Molecular dynamics (MD) simulations of hydrated sulfonated polyimide (SPI) models, one of the representative non-perfluorinated PEMs, under different temperature and humidifying conditions by removing water molecules continuously, reflecting experimental conditions of actual low humidifying fuel cell. The water channel morphology of sulfonated polyimide (SPI) models had no apparent temperature dependence. The hydrated SPI models show weak water channel formation even in a fully hydrated condition (λ = 16.4), consistent with our previous study, and they do not display significant temperature dependence on the water molecule distribution. As the λ value decreases from 16.4 to 2 (i.e., low humidifying conditions), the water molecules in the hydrated SPI models are evenly reduced. In particular, when the λ value of the hydrated SPI model decreases from 8.5 to 6, the size of the water clusters is significantly narrowed and the clusters become segregated, and this is also confirmed by an X-ray scattering analysis. As a result, the proton conducting performance of hydrated SPI models shows similar behavior with the change in water channel morphologies, which will be very important to design a novel non-perfluorinated hydrocarbon PEM with high performance for practical fuel cell systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Non-perfluorinated PEMs under low humidifying conditions were simulated by MD. </LI> <LI> The water channel morphology of SPI models had no apparent temperature dependence. </LI> <LI> The water clusters became narrowed and segregated at low λ value. </LI> <LI> Proton transport showed similar behavior with the change in water clusters. </LI> </UL> </P>