Single Fuel Cell Tests Research Articles

Enhanced Water Management in Fuel Cell Cathodes by the Application of Superhydrophobic Fluorinated Carbon Microporous Layers

Under high current density operation, the efficiency of polymer electrolyte fuel cells (PEFCs) can dramatically decrease. This is due to water accumulation at the cathode side, preventing oxygen diffusion to the electrocatalyst. As such, effective water management is of vital importance by use of a suitable gas diffusion layer (GDL) and/or microporous layer (MPL). MPLs generally consist of carbon black as the porous electron conducting phase, and polytetrafluoroethylene (PTFE) as a hydrophobic binder. Here, we instead use superhydrophobic fluorinated carbon powder in the MPL as a novel material to decrease the required PTFE content. It is confirmed that the water contact angle of the MPL can be increased from 131° to 151° by using fluorinated carbon. Moreover, the fluorinated carbon MPL shows lower oxygen transport resistance at high humidity. Furthermore, in single fuel cell tests at various temperatures and relative humidity values, the I–V performance is significantly and consistently better than for the conventional MPL. These results confirm that fluorinated carbon is a promising new material for water management in the MPLs of PEFCs.This paper is based on results obtained from project JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).1. Tailored Wettability in Fluorinated Carbon Nanoparticles Synthesized from Fluorotelomer Alcohols, E. Can, M. Nishihara, K. Sasaki, S. M. Lyth, Applied Surface Science, 157136 (2023)2. Superhydrophobic Fluorinated Carbon Powders for Prevention of Flooding in PEFCs, E. M. Can, A. Mufundirwa, T. Kitahara, M. Nishihara, K. Sasaki, S. M. Lyth, Journal of Power Sources, 548, 232098 (2022)3. Solvothermal Synthesis of Superhydrophobic Hollow Carbon Nanoparticles from Fluorinated Alcohol, S. M. Lyth, W. Ma, J. Liu, T. Daio, K. Sasaki, A. Takahara, and B. Ameduri, Nanoscale, 7, 16087 (2015)

High performance chitosan/nanocellulose-based composite membrane for alkaline direct ethanol fuel cells

Polysaccharide anion exchange membranes (AEMs) containing chitosan (CS), cellulose nanofibrils (CNFs) and CNFs quaternized with poly(diallyldimethylammonium chloride) (CNF(P)s) were developed for use in alkaline direct ethanol fuel cells (ADEFCs). The resulting composite membranes prepared by the solvent casting process based on an experimental design were comprehensively assessed for morphology, KOH uptake, swelling ratio, EtOH permeability, mechanical properties, ionic conductivity, and cell performance. The fabricated CS-based composite membranes with CNF(P) fillers were superior to the commercial Fumatech FAA-3-50 membrane in terms of Young's modulus and tensile strength (69 % and 85 % higher, respectively), ion exchange capacity (169 % higher), and ionic conductivity (228 % higher). Single fuel cell tests have shown excellent performance of the CS-based membranes with CNF and CNF(P) fillers, as they exhibited up to 86 % improvement in power density at 80 °C compared to the commercial membrane (65.1 mW/cm2 vs. 35.1 mW/cm2) and higher maximum power density at all test conditions.

Superhydrophobic fluorinated carbon powders for improved water management in hydrogen fuel cells

Under high current density operation, the efficiency of polymer electrolyte fuel cells (PEFCs) can dramatically decrease. This is due to water accumulation at the cathode side, preventing oxygen diffusion to the electrocatalyst. As such, effective water management is of vital importance by use of a suitable gas diffusion layer (GDL) and/or microporous layer (MPL). MPLs generally consist of carbon black as the porous electron conducting phase, and polytetrafluoroethylene (PTFE) as a hydrophobic binder. Here, we instead use superhydrophobic fluorinated carbon powder in the MPL as a novel material to decrease the required PTFE content. It is confirmed that the water contact angle of the MPL can be increased from 131° to 151° by using fluorinated carbon. Moreover, the fluorinated carbon MPL shows lower oxygen transport resistance at high humidity. Furthermore, in single fuel cell tests at various temperatures and relative humidity values, the I–V performance is significantly and consistently better than for the conventional MPL. These results confirm that fluorinated carbon is a promising new material for water management in the MPLs of PEFCs.

Effect of multilayer CrN/CrAlN coating on the corrosion and contact resistance behavior of 316L SS bipolar plate for high temperature proton exchange membrane fuel cell

• The CrN/CrAlN coating greatly improved the contact angle and corrosion resistance of 316L SS. • The CrN/CrAlN coating reduced the ICR and increased the surface conductivity of 316LSS. • Single fuel cell test assembled with CrN/CrAlN coating enhanced the performance of HT-PEMFC. Stainless steels have received wide attention as a substitute material for bipolar plates in high temperature proton exchange membrane fuel cell (HT-PEMFC). In the present work, the CrN, CrAlN and multilayer CrN/CrAlN coatings were deposited on 316L SS to increase the corrosion resistance and decrease the interfacial contact resistance. The deposited coatings exhibited face centered cubic phase structure and it was verified from the X-ray diffraction pattern. X-ray photo electron spectroscopy results showed the formation of both CrN and CrAlN layers on 316L SS. CrN/CrAlN coating is more helpful in water management due to low surface roughness and high contact angle in the HT-PEMFC environment. The corrosion resistance behavior of all the samples were studied in 85% H 3 PO 4 solution at 140 °C purged with H 2 (HT-PEMFC anode) and O 2 (HT-PEMFC cathode) gases. The results showed that all the coatings considerably improved the performance of 316L SS and superior corrosion resistance was observed for CrN/CrAlN multilayer coating, whose protective efficiency was 98.12% and 96.14% in the two simulated HT-PEMFC environments. The results of electrochemical impedance spectroscopic studies demonstrated higher impedance for CrN/CrAlN coating. Surface morphological studies performed after corrosion studies revealed that protection ability of CrN/CrAlN coating still remained acceptable. A very low interfacial contact resistance value of 6 mΩ cm 2 at 140 N/cm 2 was observed for CrN/CrAlN coating. Moreover, after corrosion studies, the interfacial contact resistance value of CrN/CrAlN coated 316L was much lower than that of CrN and CrAlN coatings due to the increased oxidation resistance. The maximum power density of about 0.93 W/cm 2 at 2 A/cm 2 and output voltage of 0.96 V was observed for CrN/CrAlN coating.

Concepts for preventing metal dissolution from stainless-steel bipolar plates in PEM fuel cells

The bipolar plate (BPP) is a component with vast cost-reduction potential in proton exchange membrane fuel cells (PEMFCs). Apart from mechanical and heat transfer requirements, the most desired BPP properties are high corrosion and low electrical contact resistance. In this study we confirm that due to ionic decoupling between BPPs and electrodes, the surface potentials of the BPPs remain stable even at varying operation loads. These mild potentials, in combination with low metal-ion leeching due to passive-transpassive-passive dissolution in stainless steels, suggest that low-cost carbon-coated stainless steel can readily be used as a BPP in PEMFCs. To prove this, single-fuel cell tests were carried out under realistic driving conditions, including electrochemical analysis, in-situ contact-resistance measurements, and post-mortem investigation of the membrane electrode assembly (MEA) by inductively coupled plasma trace-metal analysis, combined with electron microscopy and Auger spectroscopy of the BPPs. The results show that due to the ionic decoupling, conditions at the BPP surfaces are much less corrosive than previously thought. Furthermore, carbon-coated stainless-steel BPPs prove to be unaffected by global hydrogen starvation, which causes severe MEA degradation independent of the presence or absence of BPPs.

Hybrid Proton-Exchange Membrane Based on Perfluorosulfonated Polymers and Resorcinol-Formaldehyde Hydrogel.

Organic resorcinol–formaldehyde (RF) hydrogels were introduced into a hybrid cation-exchange membrane in order to enhance its following properties: water uptake, thermal stability, and ionic conductivity. This study was aimed to investigate the modifications induced by the RF organic clusters that form a uniform distributed network within the perflourosulfonated acid (PFSA) matrix. RF concentration was controlled by resorcinol and formaldehyde impregnation time using water or ethanol solvents. The specific morphological and structural properties were characterized by atomic force microscopy, UV–Vis, and Fourier transform infrared spectroscopy. Thermo-gravimetric analysis was employed to study the thermal stability and degradation processes of the composite membranes. Proton conductivity, as a function of relative humidity (RH) at 80 °C, was measured using in-plane four-point characterization technique. Compared to the pristine membrane, the PFSA–RF hybrid membranes showed improved thermal stability at up to 46 °C and higher ionic conductivity for low RF content, especially at low relative humidity, when using ethanol-based solvents. Single fuel cell testing on RF-based membrane–electrode assembly revealed impeccable fuel crossover and power performance at 80 °C and 40% relative humidity, delivering a 76% increase in power density compared to a reference assembled with a pristine membrane and the same catalyst loadings.

Poly(vinyl alcohol)-Based Anion Exchange Membranes for Alkaline Direct Ethanol Fuel Cells

Crosslinked anion exchange membranes (AEMs) made from poly(vinyl alcohol) (PVA) as a backbone polymer and different approaches to functional group introduction were prepared by means of solution casting with thermal and chemical crosslinking. Membrane characterization was performed by SEM, FTIR, and thermogravimetric analyses. The performance of AEMs was evaluated by water uptake, swelling degree, ion exchange capacity, OH- conductivity, and single cell tests. A combination of quaternized ammonium poly(vinyl alcohol) (QPVA) and poly(diallyldimethylammonium chloride) (PDDMAC) showed the highest conductivity, water uptake, and swelling among other functional group sources. The AEM with a combined mass ratio of QPVA and PDDMAC of 1:0.5 (QPV/PDD0.5) has the highest hydroxide conductivity of 54.46 mS cm-1. The single fuel cell tests with QPV/PDD0.5 membrane yield the maximum power density and current density of 8.6 mW cm-2 and 47.6 mA cm-2 at 57 °C. This study demonstrates that PVA-based AEMs have the potential for alkaline direct ethanol fuel cells (ADEFCs) application.

PEM Fuel Cell Performance of Cobalt Phthalocyanine Supported on CVD Graphene and Different Carbon Materials

Cobalt (II) phthalocyanine (CoPc) is investigated as an alternative catalyst to Pt to decrease the cost of polymer electrolyte membrane (PEM) fuel cell. Carbon nanotube (CNT), VulcanXC72 (V), graphene (G) and their hybridization (CNT/G, V/G, CNT/V) are used as catalyst support. Carbon supported CoPc is prepared by impregnation method using THF. Different support materials and back pressure effect are investigated for better catalytic activity and stability. Single fuel cell tests were carried out. Higher heat treatment temperatures and higher operational backpressure improves fuel cell performance. Hybridization of graphene with Vulcan gives lower performance. Hybridization of carbon nanotube and Vulcan XC72 as a catalyst support gives the best fuel cell performance. Operational parameters provided maximum power density of CNT-Vulcan 303 mW/cm2 with 0.3 mgCo/cm2 loading, 5-psi backpressure, 100% RH and 60 °C operational temperature. Figure 1

A novel hydrophilic‐modified gas diffusion layer for proton exchange membrane fuel cells operating in low humidification

A novel hydrophilic-modified gas diffusion layer (GDL) through inserting the polyacrylonitrile (PAN) into the microporous layer is fabricated to elevate the performance of the proton exchange membrane fuel cells (PEMFCs) under low humidfication. The single fuel cell test confirms that the membrane electrode assembly with 3 wt% addition of PAN in the cathode GDL exhibits a maximum power density of 0.616 W cm−2, which is 30% higher than that of conventional hydrophobic GDL (0.480 W cm−2) under low humidity. This significant enhancement in performance is attributed to the powerful wettability and the pore structure modification of the PAN. Besides, the introduction of PAN shows little influence on the performance of PEMFCs under full humidity. Our findings reported here shed new light on developing a robust GDL that can be used in both low and high humidification.

A Binary Liquid Mixture of Bioethanol-Water and Biodiesel-Water as Fuel for NSDC-LNSDCNSDC-L Direct Ethanol-Solid Oxide Fuel Cell

This research studies the possibility on using a binary liquid mixture of bioethanol-water and biodiesel-water as fuel for a NSDC-LNSDCNSDC-L single fuel cell. The ratio of bioethanol-water was 70:30, as well as the ratio of biodiesel-water. The fuel vapor flowed into the fuel cell system under the temperatures of 673, 773 and 873 K with a flow rate of 1–1.5 ml•min-1. The highest power densities were found at 673 K which are 2.984 and 1.838 mW•cm-2 for bioethanol-water and biodiesel-water, respectively. It is a promising result for a single fuel cell test with a very low rate of liquid fuel flow. Meanwhile, open circuit voltage (OCV) of the single fuel cell with bioethanol-water fuel is 1.439 V which is close to the theoretical OCV. However, OCV of the single fuel cell with biodiesel-water as fuel is 0.710 V which is lower than the theoretical OCV. Cell polarization seems still being the problem causing voltage loss during single fuel cell test.

Non Precious Metal Catalysts: A Fuel Cell and ORR Study of Thermally Synthesized Nickel and Platinum Mixed Nickel Nanotubes for PEMFC

A highly active Platinum Group Metal (PGM) and non-PGM electrocatalysts with thermally extruded nanotubes have been prepared for Proton Exchange Membrane (PEM) fuel cell by sintering Nickel zeolitic imidazole framework (Ni-ZIF). Preeminent electro-catalytic activities have been observed through single fuel cell tests and rotating disk electrode (RDE). This study involves the comparison of Oxygen Reduction Reaction (ORR) activities and fuel cell (FC) test station performance of two catalyst Nickel and Platinum mixed Nickel nanotubes (Ni NT, Ni/Pt NT) respectively. The acidic cells with corresponding Ni and Ni/Pt catalysts delivers peak power densities of 325 mWcm-2 and 455 mWcm-2 at 75 °C inside fuel cell. Our results indicate that, the synthesized Nickel nanotubes has profound effect on catalytic performance of both PGM and non-PGM electro catalysts.

Polymer grafted GO/sulfonated copolyimide proton exchange nanocomposite membrane: as a polymer electrolyte membranes fuel cell

Attaining a high performance proton exchange membrane as a suitable replacement for Nafion is one of the research priorities of fuel cell research. In this regard, we synthesized a copolyimide consisting of sulfonic acid substituents filled with different content of GO grafted sulfonated poly (urea-co-urethane) via in situ condensation polymerization. All nanocomposites showed a significant increase in thermal, mechanical properties, ion exchange capacity (IEC), water uptake (WU) and proton conductivity by incorporation of the modified GO nanosheets and the best results were found for membrane containing 1 wt% modified GO loading. The nanocomposite membrane with 1 wt% modified GO nanosheets exhibits 0.73 meq g−1 IEC and 7.3 mS cm−1 proton conductivity at room temperature. A single fuel cell test of this membrane demonstrates a maximum power density of 26.30 mW cm−2 at 0.26 V.

Assessment of the electrochemical characteristics of a Polymer Electrolyte Membrane in a reference single fuel cell testing hardware

The design of a new testing hardware for Polymer Electrolyte Membrane (PEM) single cell is presented in this paper. It has been developed with the purpose to minimise the influence from the testing hardware itself on results of performance and durability tests. This has been achieved by exposing the tested Membrane Electrode Assembly (MEA) to as far as possible uniform distribution of temperature, pressure and reactant gases composition across the active area. The new hardware aims thus at providing a reference testing platform enabling the generation of accurate experimental results and better comparison among different laboratories. The performance of this new hardware has been compared with single-serpentine channel hardware, commonly used for PEM single cell testing. Evaluation of polarisation curve and electrochemical impedance spectroscopy experimental results show that it provides better quality results which are much less affected by accumulated liquid water, thus providing better information on MEA performance.

Comparison of experimental data obtained using the reference and the single-serpentine proton exchange membrane single fuel cell testing hardware.

The paper presents testing data of single Polymer Electrolyte Membrane (PEM) fuel cell for comparing the characteristics of two different testing hardware, namely the recently developed single cell reference testing hardware and the commonly used by the research community single-serpentine testing hardware. Data are presented in form of polarisation curves, temperature, pressure and voltage distributions, as well as electrochemical impedance spectroscopy measurements for a range of current densities. The electrochemical impedance spectroscopy data are also validated using the Kramers-Kronig transformation and presented as Nyquist and Bode plots. The raw data of all mentioned results are also provided in online repository. The presented experimental data are discussed and evaluated in Assessment of the electrochemical characteristic of a Polymer Electrolyte Membrane in a “reference” single fuel cell testing hardware[1].

Controlling Near-Surface Ni Composition in Octahedral PtNi(Mo) Nanoparticles by Mo Doping for a Highly Active Oxygen Reduction Reaction Catalyst.

We report and study the translation of exceptionally high catalytic oxygen electroreduction activities of molybdenum-doped octahedrally shaped PtNi(Mo) nanoparticles from conventional thin-film rotating disk electrode screenings (3.43 ± 0.35 A mgPt-1 at 0.9 VRHE) to membrane electrode assembly (MEA)-based single fuel cell tests with sustained Pt mass activities of 0.45 A mgPt-1 at 0.9 Vcell, one of the highest ever reported performances for advanced shaped Pt alloys in real devices. Scanning transmission electron microscopy with energy dispersive X-ray analysis (STEM-EDX) reveals that Mo preferentially occupies the Pt-rich edges and vertices of the element-anisotropic octahedral PtNi particles. Furthermore, by combining in situ wide-angle X-ray spectroscopy, X-ray fluorescence, and STEM-EDX elemental mapping with electrochemical measurements, we finally succeeded to realize high Ni retention in activated PtNiMo nanoparticles even after prolonged potential-cycling stability tests. Stability losses at the anodic potential limits were mainly attributed to the loss of the octahedral particle shape. Extending the anodic potential limits of the tests to the Pt oxidation region induced detectable Ni losses and structural changes. Our study shows on an atomic level how Mo adatoms on the surface impact the Ni surface composition, which, in turn, gives rise to the exceptionally high experimental catalytic ORR reactivity and calls for strategies on how to preserve this particular surface composition to arrive at performance stabilities comparable with state-of-the-art spherical dealloyed Pt core-shell catalysts.

Various hydrophilic carbon dots doped high temperature proton exchange composite membranes based on polyvinylpyrrolidone and polyethersulfone

Novel organic-inorganic composite membranes were prepared conveniently by compositing of carbon dots (CDs) possessing different hydrophilicity into the low cost blended polymers of polyvinylpyrrolidone (PVP) and polyethersulfone (PES). The hydrophilicity of the CDs arises from its surface hydrophilic groups, which could be adjusted by controlling the reaction temperature and duration time. A series of homogeneous composite membranes doping with different hydrophilic CDs of up to about 10 wt% were obtained. Comprehensive characterizations were made in order to know the influence of different hydrophilic CDs on the properties of the prepared membranes. It is found that the doped CDs could cause the change in microphase separation and benefit proton conduction of the composite membranes. The more doped CDs, the higher the conductivity. A highest conductivity of 0.086 S cm−1 was reached by a composite membrane doped with both hydrophilic and hydrophobic CDs. Moreover, the incorporated CDs brought on the changes in properties of the composite membranes including free volume, hydrophilicity, acid doping level and swelling. A single fuel cell test was made based on the CDs blended membrane and indicating its potential to be used as the membrane electrolyte in high temperature proton exchange membrane fuel cells.

Employment of Fiber-Shaped Cobalt Modified with Gold Nanoparticles as Anode in Direct Borohydride and Hydrazine Fuel Cells

In this study, fiber-shaped cobalt was electroplated on the copper surface and modified with various amounts of gold nanoparticles (denoted as AuCofiber/Cu) with the aim to use it as the anode in direct borohydride and hydrazine fuel cells. Single fuel cell tests were performed by employing the prepared AuCofiber/Cu catalysts with the Au loadings in the range of 10.9-84.4 µgAu cm-2 as the anode and a Pt sheet as the cathode. It was found that the peаk power densities up to 162 and 188 mW cm-2 аt a temperature of 25oC were obtained from N2H4-H2O2 (DHHPFC) and NaBH4-H2O2 (DBHPFC) fuel cells, respectively. It is worth to note that the highest specific peаk power density values of 12.0 kW g–1 Аu and 14.9 kW g–1 Аu were obtаined, when employing the АuCofiber/Cu catalyst with the Аu loаding of 10.9 µgАu cm–2 аs the аnode cаtаlyst.

Carbon-Supported Bimetallic Platinum–Iron Nanocatalysts: Application in Direct Borohydride/Hydrogen Peroxide Fuel Cell

Carbon-supported bimetallic platinum–iron nanocatalysts (Pt–Fe/C) with various proportions of atoms, applied to direct borohydride/peroxide fuel cell (DBHFC) anode catalyst, are facilely prepared via a simple and low-cost chemical route in aqueous solution at ambient temperature. Transmission electron microscopy and X-ray diffraction results show the Pt–Fe alloy structure’s existence as well as the mean crystallite size of around 3 nm for Pt–Fe nanoparticles. Enhanced catalytic activity of Pt–Fe/C to BH4– electro-oxidation has been observed in electrochemical test (chronoamperometry, cyclic voltammetry, single fuel cell test, and rotating disc electrode voltammetry) results, and Pt67Fe33/C shows the best catalytic performance. High maximum power density of 65 mW cm–2 for DBHFC is acquired by using Pt67Fe33/C as anode at 25 °C. Furthermore, the electron-transfer number (n) related to BH4– oxidation is evaluated, and n of 4.9 can be achieved on Pt67Fe33/C electrode.

Employment of Fiber-Shaped Cobalt Modified with Gold Nanoparticles As Anode in Direct Borohydride and Hydrazine Fuel Cells

In this study fiber-shaped cobalt was electroplated on the copper surface and modified with various amounts of gold nanoparticles (denoted as AuCofiber/Cu) with the aim to use it as the anode in direct borohydride and hydrazine fuel cells (DBFC and DHFC). Single fuel cell tests were performed by employing the prepared AuCofiber/Cu catalysts with the Au loadings in the range of 11-84 µgAu cm-2 as the anode and a Pt sheet as the cathode. The anolyte was composed of an alkaline mixture of 1 M NaBH4 + 4 M NaOH or 1 M N2H4 + 4 M NaOH and the acidic catholyte contained 5 M H2O2 + 1.5 M HCl. The performance parameters of the fuel cell was evaluated by recording the cell polarization and obtaining the corresponding power density curves at 25 ºC. А Nаfion®N117 membrаne wаs used to sepаrаte the аnodic аnd cаthodic compаrtments of the single fuel cells. It was found that the direct N2H4-H2O2 and NaBH4-H2O2 fuel cells exhibited аn open circuit voltаge of cа. 1.7 and 1.9 V, respectively. Peаk power densities up to 162 and 188 mW cm-2 аt a temperature of 25oC were obtained from N2H4-H2O2 and NaBH4-H2O2 fuel cells, respectively. It is worth to note that the highest specific peаk power density values of ca. 12 kW g–1 Аu and 15 kW g–1 Аu were obtаined, when employing the АuCofiber/Cu catalyst with the Аu loаding of 11 µgАu cm–2 аs the аnode cаtаlyst. Acknowledgment This research was funded by a M-ERA.NET grant (No. M-ERA.NET-1/2016) from the Research Council of Lithuania.

Employment of Fiber-Shaped Co Modified with Au Nanoparticles as Anode in Direct NaBH4-H2O2 and N2H4-H2O2 Fuel Cells

In this study, fiber-shaped cobalt (Cofiber) was electroplated on the copper surface and modified with various amounts of gold nanoparticles (denoted as AuCofiber/Cu) with the aim to use it as the anode material in direct NaBH4-H2O2 (DBHPFC) and N2H4-H2O2 (DHHPFC) fuel cells. The galvanic displacement technique has been used for the deposition of Au nanoparticles onto the Cofiber surface. The AuCofiber/Cu catalysts were prepared with the Au loadings in the range of 10.9–84.4 μgAu cm−2. Single fuel cell tests were performed by employing the prepared Cofiber/Cu and different AuCofiber/Cu catalysts as the anode and a Pt sheet as the cathode. It was found that the peak power densities up to 162 mW cm−2 for DHHPFC and 188 mW cm−2 for DBHPFC were obtained at a temperature of 25°C using the AuCofiber/Cu catalyst with the Au loading of 84.4 μgAucm–2 as the anode. The highest specific peak power density values of 12018 mW mg–1Au for DHHPFC and 14954 mW mg–1Au for DBHPFC were obtained, when employing the AuCofiber/Cu catalyst with the lowest Au loading of 10.9 μgAu cm–2 as the anode material.