Influence of compressive stress on the pore structure of carbon cloth based gas diffusion layer investigated by capillary flow porometry

Gas diffusion layer (GDL) is subjected to compressive stress at high temperature along with polymer electrolyte membrane in the fabrication process and in assembling the fuel cell stacks. Compressive stress decreases the thickness of GDL, electrical conductivity, permeability, and affects the pores. Carbon cloth based GDL withstands higher strain level when compared to carbon paper and the pore structure is also disrupted to a greater extent in cloth based GDL. In the present paper, we have addressed the effects of stress on pore structure of cloth based GDL. An optimum GDL must offer low mass transport resistance in an operating PEM fuel cell. The pore size analysis of pristine GDL and GDLs pressed at different pressure levels (200, 600 & 1000 kg cm⁻²) and their characteristics are evaluated using capillary flow porometry. The compressive stress affects the three types of pores in GDL called bubble point pore, mean flow pore and smallest pore. The change in electrical resistance, wetting behavior and surface morphology is also examined as a function of compressive stress. The fuel cell performances using these GDLs pressed at different compressive stresses are also evaluated and presented. The highest PEMFC performance is achieved at a compressive stress of 200 kg cm⁻², which could be attributed to the combined effect of reduced ohmic resistance and optimized pore structure. The order of increasing performance in terms of current density is observed to be j₂₀₀ > j_Pristine > j₆₀₀ > j₁₀₀₀ at 0.15 V. The thicknesses and pore sizes of custom made GDL for optimum fuel cell performance are recommended.     

Effect of addition of rhenium to Pt-based anode catalysts in electro-oxidation of ethanol in direct ethanol PEM fuel cell

Breaking of C–C bond at low temperature to completely oxidize ethanol in direct ethanol fuel cell (DEFC) is the limiting factor for the development of DEFC as alternative source of power in portable electronic equipment. Binary and ternary Pt based catalysts with addition of Re, Pt–Re/C (20:20), Pt–Sn/C (20:20), Pt–Re–Sn/C (20:10:10) and Pt–Re–Sn/C (20:5:15) catalysts were prepared from their precursors by co-impregnation reduction method to study electro-oxidation of ethanol in DEFC. The electrocatalysts characterized by transmission electron microscope, scanning electron microscope, energy dispersive X-ray, and X-ray diffraction shows the formation of above mentioned bi- and tri-metallic catalyst with size ranges from 6 to 16 nm. Electrochemical analyses by cyclic voltammetry, linear sweep voltammetry and chronoamperometry show that Pt–Re–Sn/C (20:5:15) gives higher current density compared to that of Pt–Re/C (20:20) and Pt–Sn/C (20:20). The addition of Re to Pt–Sn/C is conducive to electro-oxidation of ethanol in DEFC. The power density obtained using Pt–Re–Sn/C(20% Pt, 5% Re, 15% Sn by wt) (30.5 mW/cm²) as anode catalyst in DEFC is higher than that for Pt–Re–Sn/C(20% Pt, 10% Re, 10% Sn by wt) (19.8 mW/cm²), Pt–Sn/C (20% Pt, 20% Sn by wt) (22.4 mW/cm²) and Pt–Re/C (20% Pt, 20% Re by wt) (9.8 mW/cm²) at 100 °C, 1 bar, with catalyst loading of 2 mg/cm² and 5 M ethanol as anode feed.     

Ethanol catalytic membrane reformer for direct PEM FC feeding

In this paper an ethanol reformer based on catalytic steam reforming with a catalytic honeycomb loaded with RhPd/CeO₂ and palladium separation membranes with an area of 30.4 cm² has been used to generate a pure hydrogen stream of up to 100 ml/min to feed a PEM fuel cell with an active area of 5 cm². The fuel reformer behavior has been extensively studied under different temperature, ethanol–water flow rate and gas pressure at a fixed S/C ratio of 1.6 (molar). The hydrogen yield has been controlled by acting upon the ethanol–water fuel flow and gas pressure.     

Modeling gas flow in PEMFC channels: Part I – Flow pattern transitions and pressure drop in a simulated ex situ channel with uniform water injection through the GDL

The two-phase flow in the gas channels of a proton exchange membrane fuel cell (PEMFC) is studied with an ex situ setup using a gas diffusion layer (GDL) as the sidewall of the channels. Air is supplied at the channel inlet manifold and water is supplied continuously and uniformly through the GDL along the length of the channel. This is different from the simultaneous air and water introduction at the inlet of the channel as studied by previous two-phase flow researchers. The GDL is compressed between the gas channels and the water chambers to simulate PEMFC conditions. The superficial velocity for air and water ranged from 0.25 to 34.5 m/s and 1.54 × 10⁻⁵ to 1.54 × 10⁻⁴ m/s, respectively. The ex situ setup was run in both vertical and horizontal orientations with two GDLs, – Baseline (Mitsubishi Rayon Co. MRC 105 with 5 wt.% PTFE and coated with an in-house MPL by General Motors) and SGL 25 BC – and three channel treatments – hydrophobic, hydrophilic, and untreated Lexan, with contact angles of 116°, 11° and 86°, respectively. No appreciable effect was noted because of the orientation, GDL type or channel coatings. The flow regime is observed at different locations along the channel and is expressed as a function of the superficial air and water velocities. Flow regime criteria are developed and validated against the range of ex situ data observations. A new variable water flow rate pressure drop model is developed in order to account for the variation of water entering the channel at multiple locations along the flow length. Pressure drop models are developed for specific flow regimes and validated against experimental data. The models are able to predict the experimental pressure drop data with a mean error of less than 14%.     

Imaging of desaturation of the frozen gas diffusion layers by synchrotron X-ray radiography

The visualization of the thawing and desaturation process on an initially saturated, frozen gas diffusion layer (GDL) with a serpentine gas flow channel was performed based on synchrotron X-ray computed tomography images. High speed CT scanning during the experiments allowed the dynamic desaturation process to be quantified under the cold-start with air purging condition. The saturation profiles and the desaturation rates were studied over the entire GDL domain, through-plane, and in selected regions of interest for localized behavior. Sigracet 35AA and 35BA GDLs were selected for the experiments to study the effects of GDL hydrophobicity. Along with the real-time saturation profiles, the average desaturation rates for the entire GDL domain over the whole purging process were 0.000186 μL cm^?2 s^?1, 0.000470 μL cm^?2 s^?1, 0.000516 μL cm^?2 s^?1 and 0.000901 μL cm^?2 s^?1 with the superficial gas velocity of the purging air at 2.88 m/s, 4.26 m/s, 5.98 m/s and 9.02 m/s, respectively. In addition, the dynamic saturation contours and 3-D GDL geometry models were constructed to show the liquid water movement through a GDL. Although the GDL desaturation curves for each experiment share similar trends, the results show that different conditions including air flow rate, GDL geometric location, initial water saturation, and GDL boundary condition could cause heterogeneous desaturation behavior on both overall and localized GDL regions. These data provide valuable information for future modeling studies that involve the thawing process in the GDL, and could be used to optimize the cell design and develop cold-start protocols.     

Enhanced low-humidity performance in a proton exchange membrane fuel cell by developing a novel hydrophilic gas diffusion layer

An ultrathin layer of hydrophilic titanium dioxide (TiO₂) is coated on the gas diffusion layer (GDL) to enhance the performance of a proton exchange membrane fuel cell (PEMFC) at low relative humidity (RH) and high cell temperature. Both of the modified and unmodified GDLs are characterized using contact angles, and the cell performance is evaluated at various RHs and cell temperatures. It is found that the modified GDL, which contains a hydrophilic TiO₂ layer between the microporous layer (MPL) and the gas diffusion-backing layer (GDBL), exhibits better self-humidification performance than a conventional GDL without the TiO₂ layer. At 12% RH and 65 °C cell temperature, the current density is 1190 mA cm⁻² at 0.6 V, and it maintains 95.8% of its initial performance after 50 h of continuous testing. The conventional GDL, however, exhibits 55.7% (580 mA cm⁻²) of its initial performance (1040 mA cm⁻²) within 12 h of testing. The coated hydrophilic TiO₂ layer acts as a mini humidifier retaining sufficient moisture for a PEMFC to function at low humidity conditions.     

Electrical/flow heterogeneity of gas diffusion layer and inlet humidity induced performance variation in polymer electrolyte fuel cells

A three-dimensional single-flow channel computational model is used to investigate the performance characteristics of polymer electrolyte fuel cells (PEFC). The combined influence of non-uniform interfacial contact resistance (ICR) and inlet relative humidity (RH), along with the heterogeneous flow properties of the gas diffusion layer (GDL) on the PEFC performance is evaluated. The study considers combinations of full and partial humidification of anode and cathode reactants. Results reveal heterogeneous GDL with non-uniform ICR distribution results in a slight ∼4.4% reduction in current density at 0.3V compared to the homogeneous case. However, under same electrical/flow heterogeneities, the current density is observed to increase by ∼19% to ∼1.3A/cm² under fully humidified anode and partially humidified cathode (i.e., RH_a|RH_c = 100%|60%) as compared to ∼1.1A/cm² under symmetric RH_a|RH_c = 100%|100%. Interesting observations are made on the temperature distribution and cathodic water fractions. The variation in anodic inlet humidity is observed to have no impact on temperature distribution in the membrane, whereas variation in cathodic inlet humidity is effective in reducing the temperature in the channel regime with a 4K (kelvin) difference among all the cases. It is noted here that the overpotential map is not an indicator for performance loss, at least at full inlet humidity. This parameter is observed to depend on water concentration in the cathode. The study provides a detailed analysis of the distribution of reactant mass fraction, water concentration, current density, temperature, cathodic overpotential, and cell performance for all the simulated cases.     

Numerical investigation on the performance of PEMFC with rib-like flow channels

An innovative flow channel inspired by the physical structure of the human rib was developed in this paper. The performance of a proton exchange membrane fuel cell (PEMFC) with the proposed rib-like flow channels under different flow patterns and relative humidity of anode (RH_a) was investigated. Compared with the conventional interdigitated flow channel (CIFC) and cross-flow channel (CRFC), the maximum current density of the counter-flow channel (COFC) was 1.06 A/cm² at 0.4 V, with enhancements of 4.95% and 2.91%, respectively. In addition, the quantity referred to as non-uniformity N was introduced to quantify the concentration distribution of oxygen, the minimum non-uniformity N of 0.17 was obtained for CRFC, and the COFC exhibited a more uniform concentration distribution of temperature as compared with the CIFC and CRFC, indicating that the COFC would prevent the occurrence of local hot spots. The maximum net power density of COFC was 6.0% and 3.0% higher than that of the CIFC and CRFC. Finally, the maximum current density of RH_a = 30% was 1.06 A/cm², which was 3.9% and 7.1% higher than that of RH_a = 60% and RH_a = 100%. The temperature with RH_a = 100% was more uniform in comparison with RH_a = 30% and RH_a = 60%, and the mass fraction of H₂ decreased with the increase of values of RH_a. The proposed rib-like flow channel can further enrich PEMFC flow channel design and afford novel insights into the application of bionics in fuel cells.     

Synthesis and characterization of NiO/GDC–GDC dual nano-composite powders for high-performance methane fueled solid oxide fuel cells

GDC (gadolinium-doped ceria) is well known as a high oxygen ionic conductor and is a catalyst for the electrochemical reaction with methane fuel leading to the oxidation of deposited carbon that can clog the pores of the anode and break the microstructure of the anode. NiO/GDC–GDC dual nano-composite powders were synthesized by the Pechini process, which were used as an AFL (anode functional layer) or anode substrates along with a GDC electrolyte and LSCF–GDC cathode. The anodes, AFL, and electrolyte were fabricated by a tape-casting/lamination/co-firing. NiO–GDC anode and NiO/GDC–GDC anode-supported unit cells were evaluated in terms of their power density and durability. As a result, the NiO/GDC–GDC dual nano-composite demonstrated an improved power density from 0.4 W/cm² to 0.56 W/cm² with H₂ fuel/air and from 0.3 W/cm² to 0.56 W/cm² with CH₄ fuel/air at 650 °C. In addition, it could be operated for over 500 h without any degradation with CH₄ fuel.     

Three-dimensional modeling of a PEMFC with serpentine flow field incorporating the impacts of electrode inhomogeneous compression deformation

The effects of compression deformation of gas diffusion layer (GDL) on the performance of a proton exchange membrane fuel cell (PEMFC) with serpentine flow field were numerically investigated by coupling two-dimensional GDL mechanical deformation model based on Finite Element Analysis and three-dimensional two-phase PEMFC model with incorporating the deformation impacts. Emphasis is located on exploring the influences of assembly pressure on the non-uniform geometric deformation and distributions of transport properties in the GDL, flow behaviors and local distributions of oxygen and current density, cell polarization curves and net power densities of the PEMFC. It was indicated that the non-uniform deformation of GDL results in inhomogeneous distributions of porosity and permeability in the GDL due to the presence of rib-channel pattern, and the transport properties in the under-rib region are greatly reduced with increasing the assembly pressure, consequently weakening the gas flow and oxygen transport in the under-rib region and increasing the non-uniformity of local current density distribution. As for the overall cell performance, however, attributed to the tradeoff between the adverse impacts of GDL compression on mass transport loss and positive effects on reducing ohmic loss, the overall cell performance is firstly increased and then decreased with increasing assembly pressure from 0 MPa to 5.0 MPa, and the maximum cell performance can be achieved at the assembly pressure of about 1.0 MPa for all cases studied. As compared with the case for zero assembly pressure, the maximum net power density of the cell can be improved by about 7.7%, 9.9%, 10.5% and 10.7% for the cathode stoichiometry ratios of 2.0, 3.0, 4.0 and 5.0@i_ref = 1 A·cm⁻², respectively. Practically, it is suggested that the assembly pressure is controlled in an appropriate range of 0.5 MPa–1.5 MPa such that the cell net power can be boosted and pressure head requirement for the pump can be maintained in a appropriate level.     

Characterization of SmBaCoFeO5+δ−Ce0.9Gd0.1O1.95 composite cathodes for intermediate-temperature solid oxide fuel cells

The performance of SmBaCoFeO_5+δ (SBCF)–xCe_0.9Gd_0.1O_1.95 (GDC) (x = 0, 10, 30, 50, 60, wt%) composite cathodes has been investigated for their potential utilization in intermediate-temperature solid oxide fuel cells (IT-SOFCs). The powder X-ray diffraction (XRD), thermal expansion coefficient (TEC) and electrochemical property measurements are employed to study the materials. The XRD results prove that there is no serious reaction between SBCF and GDC oxides even at 1000 °C. The thermal expansion behavior shows that the TEC value of SBCF cathode decreases greatly with GDC addition. The addition of GDC to SBCF cathode further reduces the polarization resistance. The lowest polarization resistance of 0.036 Ω cm² is achieved at 800 °C for SBCF–50GDC composite cathode. An electrolyte-supported fuel cell is prepared using SBCF–50GDC as cathode and NiO–GDC (65:35 by weight) as anode. The cell generates good performance with the maximum power density of 691 mW cm⁻², 503 mW cm⁻² and 337 mW cm⁻² at 800 °C, 750 °C and 700 °C, respectively. Preliminary results indicate that SBCF–50GDC is especially promising as a cathode for IT-SOFCs.     

Non-dimensional analysis of PEM fuel cell phenomena by means of AC impedance measurements

AC impedance or electrochemical impedance spectroscopy (EIS) is becoming a fundamental technique used by researchers and scientists in proton exchange membrane (PEM) fuel cell analysis and development. In this work, in situ impedance measurements are presented for a series of operating conditions in a 50 cm² fuel cell. The electrode charge transfer resistance was determined from the corresponding arcs of the Nyquist diagrams. The analyses were performed for H₂/O₂ and H₂/air operation at different stoichiometric factors and reactant gases humidification. Characteristic time scales of charge transfer processes at the different operating conditions were estimated from the corresponding Bode plots. These values were used for a non-dimensional analysis of the different fuel cell electrochemical and transport processes, namely electrochemical reaction versus GDL reactant transport. Fuel cell adapted Damkhöler numbers are thus presented, where the results indicate that the GDL diffusion transport is the limiting process for the cases under analysis, especially when air is used as oxidant. Additional analysis of channel convective mass transport versus GDL diffusive mass transport is also presented.     

An analytical analysis on the cross flow in a PEM fuel cell with serpentine flow channel

A serpentine flow channel can be considered as neighboring channels connected in series, and is one of the most common and practical channel layouts for polymer electrolyte membrane (PEM) fuel cells, as it ensures the removal of liquid water produced in a cell with good performance and acceptable parasitic load. During the reactant flows along the flow channel, it can also leak or cross directly to the neighboring channel via the porous gas diffusion layer (GDL) due to the high‐pressure gradient caused by the short distance. Such a cross flow leads to a larger effective flow area resulting in a substantially lower amount of pressure drop in an actual PEM fuel cell compared with the case without cross flow. In this study, an analytical solution is obtained for the cross flow in a PEM fuel cell with a serpentine flow channel based on the assumption that the velocity of cross flow is linearly distributed in the GDL between two successive U‐turns. The analytical solution predicts the amount of pressure drop and the average volume flow rate in the flow channel and the GDL. The solution is validated over a wide range of the thickness and permeability of the GDL by comparing the results with experimental measurements and 3‐D numerical simulations in literature. Excellent agreement is obtained for the permeability less than 10^?9 m², which covers the typical permeability values of the GDLs in actual PEM fuel cells. The solution presents an accurate and efficient estimation for cross flow providing a useful tool for the design and optimization of PEM fuel cells with serpentine flow channels. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of aluminum-doped perovskites as cathode materials for intermediate temperature solid oxide fuel cells

(Ba_0.5Sr_0.5)(Fe_1-xAl_x)O_3-δ (BSFAx, x = 0–0.2) oxides have been synthesized as novel cobalt-free cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) using a sol-gel method. The BSFAx (x = 0–0.2) materials have been characterized by X-ray diffraction and scanning electron microscopy. The electrical conductivities and electrochemical properties of the prepared samples have also been measured. At 800 °C, the conductivity drops from 15 S cm⁻¹ to 5 S cm⁻¹ when the doping level of aluminum is increased to 20%. The aluminum-doping concentration has important impacts on the electrochemical properties of BSFAx materials. The BSFA0.09 cathode shows a significantly lower polarization resistance (0.26 Ω cm²) and cathodic overpotential value (55 mV at the current density of 0.1 A cm⁻²) at 800 °C. Furthermore, an anode-supported single cell with BSFA0.09 cathode has been fabricated and operated at a temperature range from 650 to 800 °C with humidified hydrogen (∼3vol% H₂O) as the fuel and the static air as the oxidant. A maximum power density of 676 mWcm⁻² has been achieved at 800 °C for the single cell. We believe that BSFA0.09 is a promising cathode material for future IT-SOFCs application.     

Investigation of sintered stainless steel fiber felt as gas diffusion layer in proton exchange membrane fuel cells

The feasibility of using sintered stainless steel fiber felt (SSSFF) as gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs) is evaluated in this study. The SSSFF is coated with an amorphous carbon (a-C) film by closed field unbalanced magnetron sputter ion plating (CFUBMSIP) to enhance the corrosion resistance and reduce the contact resistance. The characteristics of treated SSSFF, including microscopic morphology, mechanical properties, electrical conductivity, electrochemical behavior and wettablity characterization, are systematically investigated and summarized according to the requirements of GDL in PEMFC. A membrane electrode assembly (MEA) with a-C coated SSSFF-15 GDL is fabricated and assembled with a-C coated stainless steel bipolar plates in a single cell. The initial peak power density of the single cell is 877.8 mW cm⁻² at a current density of 2324.9 mA cm⁻². Lifetime test of the single cell over 200 h indicates that the a-C coating protects the SSSFF-15 GDL from corrosion and decreases the performance degradation from 30.6% to 6.3%. The results show that the SSSFF GDL, enjoying higher compressive modulus and ductility, is a promising solution to improve fluid permeability of GDL under compression and PEMFC durability.     

Designing independent water transport channels to improve water flooding in ultra-thin nanoporous film cathodes for PEMFCs

Utilization of 3D nanostructured Pt cathodes could obviously improve performances of proton exchange membrane fuel cells (PEMFCs) owing to the reduced tortuosity and the bi-continuous nanoporous structure. However, these cathodes usually suffer from the flooding problem ascribed to the ionomer-free and nanoscale pores which are more susceptible to water condensation. In this paper, ultra-thin nanoporous metal films (100 nm) were utilized to construct PEMFC cathodes and independent transport channels were designed separately for water and gas aiming at the flooding problem. Nanoporous gold (NPG) film was used as the model support for loading Pt nanoparticles owing to its controllable and stable structure. After optimizing the polytetrafluoroethylene (PTFE) content and carbon loading in the gas diffusion layer (GDL), plasma treatment under O₂ atmosphere was used to pattern the GDL with independent water transport channels. The obtained liquid permeation coefficients and oxygen gains demonstrated the obviously improved water and O₂ transport. By using a home-made optimized GDL and a nanoporous film cathode with pore size ～60 nm, the flooding problem could be facilely solved. With a Pt loading of ～16 μg cm^?2, this 3D nanostructured cathode exhibits a PEMFC performance of ～957 mW cm^?2 at 80 °C. The Pt power efficiency is about 4 times higher than that of the commercial Pt/C cathode (50 μg cm^?2, 756 mW cm^?2). Obviously, this study provides a simple but effective methodology to solve the water flooding problem in the ultra-thin nanoporous film cathodes which is applicable for other types of 3D nanostructured PEMFC cathodes.     

New SrMo1−xCrxO3−δ perovskites as anodes in solid-oxide fuel cells

Oxides of composition SrMo_1−xCr_xO_3−δ (x = 0.1, 0.2) have been prepared, characterized and tested as anode materials in single solid-oxide fuel cells, yielding output powers higher than 700 mW cm⁻² at 850 °C with pure H₂ as a fuel. All the materials are suggested to present mixed ionic–electronic conductivity (MIEC) from neutron powder diffraction (NPD) experiments, complemented with transport measurements; the presence of a Mo⁴⁺/Mo⁵⁺ mixed valence at room temperature, combined with a huge metal-like electronic conductivity, as high as 340 S cm⁻¹ at T = 50 °C for x = 0.1, could make these oxides good materials for solid-oxide fuel cells. The magnitude of the electronic conductivity decreases with increasing Cr-doping content. The reversibility of the reduction–oxidation between the oxidized Sr(Mo,Cr)O_4−δ scheelite and the reduced Sr(Mo,Cr)O₃ perovskite phases was studied by thermogravimetric analysis, which exhibit the required cyclability for fuel cells. An adequate thermal expansion coefficient, without abrupt changes, and a chemical compatibility with electrolytes make these oxides good candidates for anodes in intermediate-temperature SOFC (IT-SOFCs).     

Graphene nanosheet–CNT hybrid nanostructure electrode for a proton exchange membrane fuel cell

This work demonstrates two-step growth of graphene nanosheets (GNS), in which carbon nanotubes (CNTs) are grown directly on a carbon cloth. GNS are subsequently constructed on the CNT surface, revealing the stand-up structure of the GNS–CNT hybrid nanostructure. The GNS–CNT hybrid nanostructure shows Nernstian and fast electron-transfer kinetics for electrochemical reactions of Fe(CN)₆^3−/4−. A 0.1 mg cm⁻² Pt/GNS–CNT is used in the cathode of a proton membrane exchange fuel cell, in which the maximum power density is 1072 mW cm⁻² at 80 °C under H₂/O₂. In addition to a low-resistance electron-transfer pathway, the GNS–CNT hybrid nanostructure also provides numerous edge planes with strong electrochemical activity, ultimately enhancing electrochemical activity and fuel cell performance.     

Electrochemical durability of gas diffusion layer under simulated proton exchange membrane fuel cell conditions

An effective ex-situ method for characterizing electrochemical durability of a gas diffusion layer (GDL) under simulated polymer electrolyte membrane fuel cell (PEMFC) conditions is reported in this article. Electrochemical oxidation of the GDLs are studied following potentiostatic treatments up to 96 h holding at potentials from 1.0 to 1.4 V (vs.SCE) in 0.5 mol L⁻¹ H₂SO₄. From the analysis of morphology, resistance, gas permeability and contact angle, the characteristics of the fresh GDL and the oxidized GDLs are compared. It is found that the maximum power densities of the fuel cells with the oxidized GDLs hold at 1.2 and 1.4 V (vs.SCE) for 96 h decreased 178 and 486 mW cm⁻², respectively. The electrochemical impedance spectra measured at 1500 mA cm⁻² are also presented and they reveal that the ohmic resistance, charge-transfer and mass-transfer resistances of the fuel cell changed significantly due to corrosion at high potential.     

Experimental investigation on water and heat management in a PEM fuel cell using response surface methodology

Water and heat management are the most critical issues for the performance of proton exchange membrane (PEM) fuel cells. They can be provided by keeping hydrogen flow rate, oxygen flow rate, cell temperature and humidification temperature under control. In this study, the effects of these parameters on the power density of proton exchange membrane (PEM) fuel cell which has 25 cm² active area have been examined experimentally using hydrogen on the anode side and oxygen on the cathode side. Response Surface Methodology (RSM) has been applied to optimize these operation parameters of proton exchange membrane (PEM) fuel cell. The test responses are the maximum output power density. ANOVA (analysis of variance) analyses are used to compute the effects and the contributions of the various factors to the fuel cell maximal power density. The use of this design shows also how it is possible to reduce the number of experiments. Hydrogen flow rate, oxygen flow rate, humidification temperature and cell temperature were the main parameters to have been varied between 2.5–5 L/min, 3–5 L/min, 40–70 °C and 40–80 °C in the analyses. The maximum power density was found as 241.977 mW/cm².