Performance of the gold-plated titanium bipolar plates for the light weight PEM fuel cells

In this present work, we are attempting to develop a light weight and corrosion resistant bipolar plate for the proton exchange membrane fuel cell. A titanium bipolar plate substrate has been chosen as the base metal due to its low cost, ease of manufacture into stampable bipolar plates, and its light weight. Our approach to obtain a smaller and lighter weight single fuel cell is to coat titanium with a corrosion resistant coating. Gold (Au) was investigated. The cell performance of the gold-plated bipolar plates is close to and even better than the PEM fuel cells with graphite and pure titanium bipolar plates. Gold-plated titanium bipolar plates can be employed to produce fuel cells with light weight, low coating cost and low contact resistance, ideal for portable applications.     

Performance of PEMFC stack using expanded graphite bipolar plates

The bipolar plates are in weight and volume the major part of PEM fuel cell stack, and also a significant effect to the stack cost. To develop the low-cost and low-weight bipolar plate for PEM fuel cell, we have developed a kind of cheap expanded graphite plate material and a production process for fuel cell bipolar plates. The plates have a high electric conductivity and low density, and can be stamped directly forming fuel cell bipolar plates. Then, 1 and 10 kW stacks using expanded graphite bipolar plates are successfully assembled. The contact resistance of the bipolar plate is investigated and the electrochemical performances of the fuel cell stacks are tested. Good fuel cell performance is obtained and the voltage distribution among every single cell in the stacks is very uniform.     

New electroplated aluminum bipolar plate for PEM fuel cell

Further improvement in the performance of the polymer electrolyte membrane fuel cells as a power source for automotive applications may be achieved by the use of a new material in the manufacture of the bipolar plate. Several nickel alloys were applied on the aluminum substrate, the use of aluminum as a bipolar plate instead of graphite is to reduce the bipolar plate cost and weight and the ease of machining. The electroplated nickel alloys on aluminum substrate produced a new metallic bipolar plate for PEM fuel cell with a higher efficiency and longer lifetime than the graphite bipolar plate due to its higher electrical conductivity and its lower corrosion rate. Different pretreatment methods were tested; the optimum method for pretreatment consists of dipping the specimen in a 12.5% NaOH for 3 min followed by electroless zinc plating for 2 min, then the specimen is dipped quickly in the electroplating bath after rinsing with distilled water. The produced electroplate was tested with different measurement techniques, chosen based on the requirement for a PEM fuel cell bipolar plate, including X-ray diffraction, EDAX, SEM, corrosion resistance, thickness measurement, microhardness, and electrical conductivity.     

Expanded graphite-based electrically conductive composites as bipolar plate for PEM fuel cell

In this study, expanded graphite-based composite bipolar plates are developed from expanded graphite (EG), which is synthesized by chemical intercalation of natural graphite and rapid expansion at high temperature. The expanded graphite synthesized in this study has an expansion ratio between 75–100 cc/gm. The composite bipolar plate with varying weight percentage of EG gives different bulk density, electrical conductivity, mechanical properties and air tightness. The critical weight percentage of filler content is 50 to achieve the desired electrical conductivity and mechanical properties of bipolar plate as per U.S. DOE targets. The composite bipolar plate with 50 wt% of EG gives bulk density of 1.50 g/cm³, electrical conductivity >120 S/cm, bending strength 54 MPa, modulus 6 GPa and shore hardness 50. I–V characteristic of a cell assembly with EG-based composite plates are similar with the performance of a cell with commercial composite plates. These lightweight bipolar plates reduced the volume and weight of ultimate fuel cell stack and helped in improving the fuel cell performance.     

Electrically conductive polymer composite coating on aluminum for PEM fuel cells bipolar plate

Aluminum has many advantages for commercial bipolar plate of PEM fuel cell such as light weight, low cost and easy manufacturing. However, it has a low corrosion resistance under a PEM fuel cell operation condition that is a special issue of all metal bipolar plates. In this study, polypropylene composite coated with aluminum bipolar plates were fabricated to improve the corrosion resistance. However, contact resistance of polymer composite coated aluminum bipolar plate is highly increased due to high contact resistance between aluminum substrate and composite layer. Two different types of inter layers were added to improve the contact resistance. Carbon paper attached and carbon black added samples were fabricated between aluminum substrate and composite. Polyamide-imide/carbon black composite adhesive was used for carbon paper attached on the aluminum plate. The contact resistance of carbon paper attached sample was lower than that of carbon black added sample. And, corrosion resistance was tested by potentiodynamic and potentiostatic methods. The composite coated aluminum attached to carbon paper exhibited properties suitable for PEM fuel cells.     

Effect of plastic deformation on the corrosion resistance of ferritic stainless steel as a bipolar plate for polymer electrolyte membrane fuel cells

Stainless steel is one of the best candidate materials for bipolar plate of polymer electrolyte membrane fuel cell (PEMFC) and there have been several manufacturing techniques for stainless steel bipolar plate. The deformation from manufacturing process for bipolar plate can induce the corrosion problem of bipolar plate. The deformed and the stamped stainless steels were examined by evaluating the corrosion resistance to understand the effect of the deformation on the stainless steel as a bipolar plate. The deformation of the stainless steel can significantly affect the corrosion resistance and the deformation from the shaping process for bipolar plate can induce the local anodic sites on the bipolar plate. Therefore, from the corrosion point of view, the shaping process for the bipolar plate is an important factor and the corrosion possibility by shaping process should be considered when selecting the optimum shaping method.     

Aluminate cement/graphite conductive composite bipolar plate for proton exchange membrane fuel cells

Aluminate cement/graphite conductive composite bipolar plate for proton exchange membrane fuel cells (PEMFC) was prepared by mold pressing at room temperature. The effect of size of graphite particles on the conductivity and the flexural strength of composite bipolar plate were discussed. Resistance to acid corrosion, thermal property and pore size distribution of this composite bipolar plate were also investigated in this paper. The experiment results show that the conductivity and the flexural strength of this composite bipolar plate can be improved by choosing uniform size graphite as conductive fillers. The corrosion current is about 10^−4.5 A cm⁻² from polarization curves of this composite bipolar plate, which shows that this composite bipolar plate is acid corrosion-resistant. Al and Ca ions may leach from this composite bipolar plate after 1 M H₂SO₄ acid corrosion. But Al and Ca ions leaching from this composite bipolar plate are only a little percentage of the total Al and Ca ions content in the composite bipolar plate after acid corrosion at 30 °C. This composite bipolar plate is also thermally stable from room temperature to 400 °C. The large amount of pore in this composite bipolar plate is gel capillary pores because of the hydration and solidification of aluminate cement, which make it possess humidifying function during the PEMFC operating.     

Bipolar plate design and fabrication using graphite reinforced composite laminate for proton exchange membrane fuel cells

A bipolar plate is designed to have high electric conductivity, low corrosion and good mechanical strength characteristics. The two most common materials adopted for bipolar plates are carbon and metal. The carbon bipolar plate has good electric conductivity and corrosion resistance but brittle. The metal bipolar plate has good mechanical strength, acceptable electrical conductivity but worse corrosion resistance. The main objective of this paper is to design and fabricate graphite composite laminate based PEMFC bipolar plate. A thermoset type phenolic resin is adopted as the matrix with a plain weave type woven graphite fiber cloth adopted as the composite laminate reinforcement. In the fabrication process, thermoset phenol-formaldehyde resin is first printed onto the plain-weave woven carbon fiber cloth and the waiting until air-dry as prepregs. Several layers of prepregs were then stacked into a mold and heated. The resin contained in the prepregs melted and cured into a composite laminate. The carbonization process is further conducted to increase the electric conductivity. The flow channels are carved and the bipolar plate is completely fabricated. The developed bipolar plates are assembled into a single cell PEMFC and tested. The composite bipolar plate performance with or without carbonization are also studied. The back side bipolar plate electric conductivity would also significantly affect the cell performance. Therefore, increasing the back side conductivity could increase the cell performance.     

A graphite-coated carbon fiber epoxy composite bipolar plate for polymer electrolyte membrane fuel cell

A PEMFC (polymer electrolyte membrane fuel cell or proton exchange membrane fuel cell) stack is composed of GDLs (gas diffusion layers), MEAs (membrane electrode assemblies), and bipolar plates. One of the important functions of bipolar plates is to collect and conduct the current from cell to cell, which requires low electrical bulk and interfacial resistances. For a carbon fiber epoxy composite bipolar plate, the interfacial resistance is usually much larger than the bulk resistance due to the resin-rich layer on the composite surface.In this study, a thin graphite layer is coated on the carbon/epoxy composite bipolar plate to decrease the interfacial contact resistance between the bipolar plate and the GDL. The total electrical resistance in the through-thickness direction of the bipolar plate is measured with respect to the thickness of the graphite coating layer, and the ratio of the bulk resistance to the interfacial contact resistance is estimated using the measured data. From the experiment, it is found that the graphite coating on the carbon/epoxy composite bipolar plate has 10% and 4% of the total electrical and interfacial contact resistances of the conventional carbon/epoxy composite bipolar plate, respectively, when the graphite coating thickness is 50 μm.     

管理与技术并重的企业清洁生产工作研究

质子交换膜燃料电池（PEMFC）以其能量转化率高、低排放、能量和功率密度高等优点被认为是适应未来能源和环境要求的理想动力源之一。双极板是质子交换膜燃料电池组中的关键功能部件之一,而且时电池组的成本、体积和质量有直接影响。开发同时具有优良的综合性能和低成本的双极板是质子交换膜燃料电池实现产业化的必然要求。综述了目前各种双极板材料的研发现状,并对各种材料进行了比较,提出了双极板材料的发展趋势。     

Preparation and properties of carbon nanotube-reinforced vinyl ester/nanocomposite bipolar plates for polymer electrolyte membrane fuel cells

Novel multiwalled carbon nanotubes (MWNTs) were prepared using poly(oxypropylene)-backboned diamines of molecular weights M_w 400 and 2000 to disperse acid-treated MWNTs, improving the performance of composite bipolar plates in polymer electrolyte membrane fuel cells. A lightweight polymer composite bipolar plate that contained vinyl ester resin, graphite powder and MWNTs was fabricated using a bulk molding compound (BMC) process. Results demonstrate that the qualitative dispersion of MWNTs crucially determined the resultant bulk electrical conductivity, the mechanical properties and the physical properties of bipolar plates. The flexural strength of the composite bipolar plate with 1 phr of MWNTs was approximately 48% higher than that of the original composite bipolar plate. The coefficient of thermal expansion of the composite bipolar plate was reduced from 37.00 to 20.40 μm m⁻¹ °C⁻¹ by adding 1 phr of MWNTs, suggesting that the composite bipolar plate has excellent thermal stability. The porosity of the composite bipolar plate was also evaluated. Additionally, the bulk electrical conductivity of the composite bipolar plate with different MWNTs types and contents exceeds 100 S cm⁻¹. The results of the polarization curves confirm that the addition of MWNTs leads to a significant improvement on the single cell performance.     

High-durability titanium bipolar plate modified by electrochemical deposition of platinum for unitized regenerative fuel cell (URFC)

The electrochemical deposition of platinum on a titanium bipolar plate (Pt/Ti) was studied for applications in a unitized regenerative fuel cell (URFC). Platinum deposition on the titanium plate was carried out in the platinum precursor solution (1.8 g dm⁻³) at constant acidity (pH 1.0) and temperature (90 °C). The pre-treatment of the titanium plate and the applied deposition current density were optimized to obtain uniform deposition of platinum on the titanium plate. New bipolar plates were prepared using the optimized deposition process and were used in a URFC. Electrochemical deposition of platinum on the titanium plate can effectively prohibit the formation of a passive oxide layer and corrosion on the surface of the bipolar plate, leading to lower resistance and better performance. In addition, the stability of URFC performance after the operation of the cell at 2.0 V for 1 h was significantly improved by the platinum deposition on the titanium bipolar plate. This improvement was mainly due to reduced corrosion on the surface of the bipolar plate.     

全钒液流电池用电极及双极板研究进展

全钒氧化还原液流储能电池是一种新型的储能装置,电极及双极板是其关键材料。介绍了全钒液流储能电池的两种电极（金属电极、碳素电极）和三种双极板（金属双极板、碳塑双极板和石墨双极板）以及一体化电极双极板的研究进展。     

质子交换膜燃料电池双极板材料研究进展

介绍了质子交换膜燃料电池双极板，着重介绍了质子交换膜燃料电池双极板的选材：金属材料，石墨材料，石墨／树脂复合材料，纤维增强石墨／树脂复合材料，对质子交换膜燃料电池双极板的选材做出了展望。     

Materials and design development for bipolar/end plates in fuel cells

Bipolar/end plate is one of the most important and costliest components of the fuel cell stack and accounts to more than 80% of the total weight of the stack. In the present work, we focus on the development of alternative materials and design concepts for these plates. A prototype one-cell polymer electrolyte membrane (PEM) fuel cell stack made out of SS-316 bipolar/end plate was fabricated and assembled. The use of porous material in the gas flow-field of bipolar/end plates was proposed, and the performance of these was compared to the conventional channel type of design. Three different porous materials were investigated, viz. Ni–Cr metal foam (50 PPI), SS-316 metal foam (20 PPI), and the carbon cloth. It was seen that the performance of fuel cell with Ni–Cr metal foam was highest, and decreased in the order SS-316 metal foam, conventional multi-parallel flow-field channel design and carbon cloth. This trend was explained based on the effective permeability of the gas flow-field in the bipolar/end plates. The use of metal foams with low permeability values resulted in an increased pressure drop across the flow-field which enhanced the cell performance.     

A single-type aluminum/composite hybrid bipolar plate with surface modification for high efficiency PEMFC

An aluminum/composite hybrid bipolar plate with a bypass aluminum channel has been developed. The mechanical abrading technique and electromagnetic-carbon technique are employed for surface modification of aluminum and composite, respectively. The optimum processes of surface modification techniques for aluminum and composite are investigated to promote intimate contact between aluminum and carbon fibers of composite for low electrical resistance. After the surfaces of the aluminum and carbon fiber prepregs are treated with the surface modification techniques, they are co-cured with the single-type of bipolar plate to lower the electrical contact resistance. In this study, it has been found that the hybrid bipolar plate has only 3% of the electrical resistance of the conventional composite bipolar plates.     

Contact mechanics approach to determine contact surface area between bipolar plates and current collector in proton exchange membrane fuel cells

A significant portion of the power loss in a fuel cell stack can be attributed to the contact resistance between the gas diffusion layer/bipolar plate and the current collector/bipolar plate interfaces, especially when an oxide layer is formed on a stainless steel bipolar plate. Researchers have already studied methods to decrease the contact resistance between fuel cell components, but never has a theoretical contact mechanics model been applied to contact resistance problems in fuel cells. Therefore, the purpose of this research is to utilize a theoretical contact mechanics model in order to study real contact area in fuel cell components as a function of surface roughness, material properties, and clamping force. Specifically, the effects of bipolar plate surface roughness, coating thickness of the gold plating on the current collector, and the clamping force on real contact area have been studied. It was found that smoother materials, thicker gold coating, and higher clamping force resulted in a higher real percentage contact area.     

Preparation and properties on the graphite/polypropylene composite bipolar plates with a 304 stainless steel by compression molding for PEM fuel cell

Graphite/polymer composites have high corrosion resistance, low contact resistance and low fabrication cost but low cell efficiency and mechanical strength. This study examined the electrical and mechanical properties of graphite/polypropylene composite bipolar plates. Carbon nanotubes (CNTs) were used to improve the electrical properties of the graphite/PP composites. Although the electrical properties increased when excess conducting filler was added to the composite, the mechanical strength decreased significantly. 304 stainless steel (304 SS) plates with different thicknesses were used as the support material of a graphite/PP composite bipolar plate. The 304 SS-supported graphite/PP composite bipolar plate had an optimum CNTs/graphite/PP composite composition of 1.2, 83 and 17 wt.%, respectively. The flexural strength of the 304 SS-supported graphite/PP composites increased from 35 to 58 MPa with increasing 304 SS thickness from 0.5 to 1 mm. The power density of the graphite bipolar plate and 304 SS-supported graphite/PP composite bipolar plate were 968 and 877 mW cm⁻², respectively. The 304 SS complemented the mechanical strength of the graphite/PP composite bipolar plate as well as the cell efficiency.     

Preparation and properties of high performance nanocomposite bipolar plate for fuel cell

This study aims at developing lightweight and high performance composite bipolar plates for use in polymer electrolyte membrane fuel cells (PEMFCs). The thin polymer composite bipolar plates (the thickness <1.5 mm) containing of vinyl ester resin, graphite powder, organoclay have been fabricated by bulk molding compound (BMC) process. Organoclay was prepared by ionic exchange of montmorillonite (MMT) with three different molecular weight (M_w) of poly(oxypropylene)-backboned diamine intercalating agents. Results indicate that the basal spacing and content of MMT varied with M_w of POP-diamines are critical in determining the resultant mechanical properties for bipolar plates. Flexural strength of MMT composite plates was increased from 30.21 to 45.66 MPa by adding 2 phr of MMT. The flexural strength of the plate was also ca. 38% higher than the pristine graphite plate as the basal spacing of MMT was increased from 1.71 to 5.43 nm. Meanwhile, the unnotched impact strength of the composite plates was increased from 58.11 to 80.21 J m⁻¹. The unnotched impact strength of the plate was ca. 30% higher than that of the original graphite plates as the basal spacing of MMT was increased from 1.71 to 5.43 nm. The limiting oxygen index (LOI) and the UL-94 test revealed that the bipolar plate possesses excellent flame retardant with LOI >50 and UL-94-V0. The thermal decomposition temperature of each MMT composite plate is also higher than 250 °C. In addition, the bulk electrical conductivity of the bipolar plate with different MMT contents and basal spacing of MMT is higher than 100 S cm⁻¹. The corrosion current is less than 10⁻⁷ A cm⁻². Results confirm that the addition of MMT leads to a significant improvement on the performance of the composite bipolar plate.     

Fabrication of high strength and a low weight composite bipolar plate for fuel cell applications

The bipolar plate is one of the most important components in a PEM fuel cell. A polymer composite bipolar plate possessing high strength (81 MPa) and high stiffness (20 GPa) has been developed by making use of carbon fiber network in a specific form as the filler component. Such high strength is very much desired, especially when the fuel cells are used for mobile applications, since it is the bipolar plate that provides mechanical support to all the other cell components. The addition of carbon black and the effect of particle size of the natural graphite flakes used as other reinforcements also play a crucial role in controlling the physical and electrical properties of the composite plates. The plate when used in the unit fuel cell assembly showed I–V performance comparable to that of the commercially available bipolar plates.