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The article presents the results of research and an analysis of the possibility of using sinters made of graphite powder as a material dedicated to the production of bipolar plates for low-temperature fuel cell. The use of powder metallurgy technology allows for the production of materials that meet the requirements for fuel cell elements for the construction of elements closing a single cell (bipolar or monopolar plates) or interconnectors. The morphological and chemical analysis of graphite powder, microstructural analysis of the produced graphite sinter, and the analysis of functional properties, i.e., porosity, roughness, and corrosion resistance under operating conditions of a low-temperature fuel cell, were performed. The corrosion resistance of the graphite sinter was tested in anodic conditions (in a corrosive environment saturated with hydrogen) and in cathodic conditions (in a corrosive environment saturated with oxygen). Graphite sinters show high resistivity in both tested corrosive environments, which allows the use of powder metallurgy technology for serial production of covers for low-temperature fuel cells. [ABSTRACT FROM AUTHOR]

Here, we report the growth of improved quality graphene thin film by a modified method using shellac as a low-cost and eco-friendly carbon source on three different substrates. We chose stainless steel (SS 316) plates used as a solid surface, nickel foam (NiF) representative of a solid porous substrate, and carbon fiber fabric (CFF) as a porous-flexible substrate. The graphene characteristic is found to be substrate-dependent in this single-step method. Uniform multilayer graphene is grown on SS316. In the case of Ni foam, the as-synthesized graphene exhibits high quality with relatively low defects. It was troublesome to grow uniform graphene on flexible CFF due to the low wettability of precursor solution. The substrate was required to modify with a thin (∼60 nm) layer of Ni deposition. The transfer-free method of graphene on CFF was assured by etching Ni via an acid treatment. Graphene coated SS316 used as bipolar plate exhibits superior corrosion resistance with corrosion current density I corr ∼1.2 μA/cm2 and much lower interfacial contact resistance ICR ∼7.7 mΩ cm2. Graphene coated Ni foam was utilized as electrodes in supercapacitors which show large areal capacitance ∼1.7 F/cm2. Besides, graphene coated CFF shows sheet resistance ∼50% lower than that of uncoated CFF. [Display omitted] • G/SS316, G/Ni foam and G/CFF were synthesized via a single-step method. • G/SS316 has long-term stability in a chloride environment. • DCG/SS316 bipolar plate has low Icorr ∼1.20 μA/cm2 and very low ICR ∼7.7 mΩ.cm2. • The supercapacitor with G/Ni foam electrode has high areal capacitance ∼1.7 F/cm2. • G/CFF has lower sheet resistance ∼13 Ω/□ compared to that (∼20 Ω/□) of bare CFF. [ABSTRACT FROM AUTHOR]

Electrolysis coupled with renewable energy resources is the most promising method for green hydrogen production. Polymer electrolyte membrane water electrolyzer (PEMWE) has attracted attention due to its ability to produce high-purity, compressed hydrogen at relatively mild operating temperatures (70°C-90°C). The highest cost contributor of the PEMWE stack are the bipolar plates (BPPs). Owing to the severe operating conditions (acidity from the membrane and high localized oxygen concentration) of the PEMWE stack, appropriate material and fabrication are crucial to ensure high performance and durability. The role of BPPs in mass transport and electrical charge transfer must be further understood and correlated to its specific application in PEMWE. At the most basic level, BPPs must have low interfacial contact resistance and high corrosion resistance to withstand the conditions within the stack. The most common base materials for BPP construction include austenitic stainless steel (SS316 and SS403) and Ti due to their flexural strength and ease of mass production. A coating layer is also necessary to protect the substrate from corrosion, and the most popular materials include TiN and other noble metals with nonpassivated oxides and reliable electrical conductivity. The compromise between material robustness and cost is currently a delicate balance toachieve. [ABSTRACT FROM AUTHOR]

The aim of this essay is to explore a new method to prepare a graphite coating on the surface of copper foil. In our study, we find that when the treated copper foil is buried in natural flake graphite powder and heated to 900°C for 1 h, the surface of copper foil grows a graphite coating. The graphite coating on the surface of copper foil increases the corrosion resistance under the simulated proton exchange membrane fuel cell environment. At the same time, graphite coating also increases corrosion potential and is higher than the anode working potential. This keeps the anode in a cathodic protection state and avoids the generation of metal ions. Compared to the substrate, the coated potentiostatic polarization for 4 h shows that it is not only corrosion current density can get reduced by an order of magnitude but also can quickly reach a steady state. The value of the copper with graphite coating in interfacial contact resistance is ∼18.4 mΩ cm2 under 1.4 MPa, which is also reaching the Department of Energy targets. [ABSTRACT FROM AUTHOR]

Water electrolysis is a process that can produce hydrogen in a clean way when renewable energy sources are used. This allows managing large renewable surpluses and transferring this energy to other sectors, such as industry or transport. Among the electrolytic technologies to produce hydrogen, proton exchange membrane (PEM) electrolysis is a promising alternative. One of the main components of PEM electrolysis cells are the bipolar plates, which are machined with a series of flow distribution channels, largely responsible for their performance and durability. In this work, AISI 316L stainless steel bipolar plates have been built by additive manufacturing (AM), using laser powder bed fusion (PBF-L) technology. These bipolar plates were subjected to ex-situ corrosion tests and assembled in an electrolysis cell to evaluate the polarization curve. Furthermore, the obtained results were compared with bipolar plates manufactured by conventional machining processes (MEC). The obtained experimental results are very similar for both manufacturing methods. This demonstrates the viability of the PBF-L technology to produce metal bipolar plates for PEM electrolyzers and opens the possibilities to design new and more complex flow distribution channels and to test these designs in initial phases before scaling them to larger surfaces. • Bipolar plates were developed by additive manufacturing and conventional machining. • Laser powder bed fusion technology was used to manufacture AISI 316 bipolar plates. • Polarization curve and corrosion test were evaluated for both manufacturing methods. • Experimental results show very similar results for both manufacturing methods. [ABSTRACT FROM AUTHOR]

Proton exchange membrane water electrolysis (PEMWE) is a green hydrogen production technology with great development prospects. As an important part of PEMWE, bipolar plates (BPs) play an important role and put forward special requirements due to the harsh environments on both the anode and cathode. Recently, metal-based BPs, particularly stainless steel and titanium BPs have attracted much attention from researchers all over the world because of their advantages of high corrosion resistance, low resistivity, high thermal conductivity, and low permeability. However, these metallic BPs are still prone to being oxidized and are facing with hydrogen embrittlement problems in the PEMWE working environment, which would result in reduced output power and premature failure of the PEMWE stack. In order to reduce the corrosion rate and maintain low interfacial contact resistance, the surface modification of the metallic BPs with protective coatings, such as precious metals (e.g., Au, Pt, etc.) and metal nitrides/carbides, etc., have been extensively investigated. However, the above-mentioned coating materials are restricted by the high-cost materials, complex equipment, and the complicated operation process. In this review, the surface modification of metallic BPs based on silane treatment, conductive polymers, e.g., polyaniline (PANI) and polypyrrole (PPy) as well as some nanoparticles-promoted polymer hybrid coatings which have been investigated for PEMWE, are summarized and reviewed. As for the silane treatment, the dense silane can not only effectively enhance the corrosion resistance but also improve the adhesion between the substrate and the conductive polymers. As for PANI and PPy, the typical value of corrosion current density of a PANI coating is 5.9 μA cm−2, which is significantly lower than 25.68 μA cm−2 of the bare metal plate. The introduction of nanosized conductive particles in PANI can further reduce the corrosion current density to 0.15 μA cm−2. However, further improvement in the electrical conductivity is still desired to decrease the interface contact resistance (ICR) to be lower than 10 mΩ cm2. In addition, serious peeling off of the coating during long-term operation also needs to be solved. Typically, the conductive polymer reinforced by graphene, noble metals, and their compounds in the form of nanoparticle-promoted polymer hybrid coatings could be a good choice to obtain higher corrosion resistance, durability, and conductivity and to extend the service life of PEMWE. Especially, nanoparticle-promoted polymer hybrid coatings consisting of polymers and conductive noble metals or nitrides/carbides can be controlled to balance the conductivity and mechanical properties. Due to the advantages of a simple preparation process, low cost, and large-scale production, nanoparticle-promoted polymer hybrid coatings have gradually become a research hotspot. This review is believed to enrich the knowledge of the large-scale preparation process and applications of BPs for PEMWE.

In this work, the effects of inserting an interlayer on the anti-corrosion performance of amorphous carbon (a-C) films in a simulated Proton Exchange Membrane Fuel Cell (PEMFC) environment have been systematically studied. Four a-C films with different interlayers, namely C Cr, C-Cr-N, CrN and Cr, were prepared on 316L stainless steel substrates using unbalanced magnetron sputtering. The surface/fractural morphologies, carbon bonding structure and the anti-corrosion performance of the 4 films were observed/characterized in detail. The nanostructure and composition evolution from the film surface down to the film-substrate interface before and after electrochemical tests were also analysed via high resolution transmission electron microscopy (HRTEM). Results indicate that a-C films with C Cr and C-Cr-N interlayers display superior corrosion resistance compared to undoped samples and those lacking an interlayer, with the lowest self-corrosion current density (i.e. 2.1 × 10−7 A/cm2, C-Cr-N interlayer) being nearly two orders of magnitude lower than that of the substrate (i.e. 1.1 × 10−5 A/cm2). The doped C-Cr-N interlayer plays a vital role in the corrosion resistance of the samples by accelerating oxidation of surface defect locations, inhibiting the continuous penetration of electrolyte, and improving corrosion resistance. Additionally, a-C films with a C-Cr-N interlayer exhibited an outstanding interface contact resistance (ICR) value (~3.5 mΩ/cm2) than that with a CrN interlayer (~30 mΩ/cm2) or the 316L substrate (~100 mΩ/cm2) at a typical contact pressure of 1.5 MPa. All 4 films demonstrate obviously improved hydrophobicity (contact angles against distilled water under room temperature up to 94.2°) compared to the substrate (75.8° under identical condition). In a word, this study proves that the strategy of inserting an appropriately designed interlayer (with the ternary C-Cr-N being most promising) to a-C films could alter and enhance the anti-corrosion, ICR and hydrophobic properties of 316L, proposing valuable solutions for high-performance bipolar plates (BPs) in the PEMFC industry. [ABSTRACT FROM AUTHOR]

Metal materials such as stainless steel (SS) and titanium alloys have been considered as ideal materials for bipolar plates (BPs) in proton exchange membrane fuel cells (PEMFCs) owing to high electrical conductivity, high thermal conductivity, good mechanical strength and processability. However, metal BPs would be corroded in the acidic working condition of PEMFC. In recent years, conducting polymer coatings (CPCs) have attracted much attention in the corrosion protection of metal BPs for the good corrosion resistance and conductivity. In this paper, we systematically review the recent advances in CPCs for metal BPs based on the two categories of non-intrinsic conducting polymer (NICP) coatings and intrinsic conducting polymer (ICP) coatings. The progress of NICP coatings for metal BPs mainly focuses on the three types of conducting fillers: noble metal materials, carbon materials and transition metal compound materials, while the progress of ICP coatings for metal BPs is discussed based on the three modification strategies: doping modification, nanomaterial modification, and bilayer coatings. Furthermore, the challenges and perspectives of CPCs coatings for metal BPs are also discussed, which would help to provide guidance for the further research of CPCs for metal BPs. In this paper, we systematically review the recent advances in conducting polymer coatings (CPCs) for metal bipolar plates (BPs) based on the two categories of non-intrinsic conducting polymer coatings (NICP) and intrinsic conducting polymer (ICP) coatings. The progress of NICP coatings for metal BPs mainly focuses on the three types of conducting fillers: noble metal materials, carbon materials and transition metal compound materials, while the progress of ICP coatings for metal BPs are discussed based on the three modification strategies: doping modification, nanomaterial modification, and bilayer coatings. [Display omitted] • The advances in conducting polymer coatings for metal bipolar plates are systematically summarized. • Three types of conducting fillers for non-intrinsic conducting polymer coatings are introduced. • Three modification strategies for intrinsic conducting polymer coatings are introduced. • The challenges and perspectives of conducting polymer coatings for metal bipolar plates are discussed. [ABSTRACT FROM AUTHOR]

In this work, pulse electrodeposition method was proposed to directly deposit amorphous carbon coating (ACC) onto 316L stainless steel substrate in choline chloride-ethylene glycol deep eutectic solvent (DES) mixed with ammonium chloride (NH 4 Cl) to fabricate bipolar plates. The obtained dense ACC has a thickness of ∼400 nm. Potentiodynamic and potentiostatic polarization tests demonstrated that the corrosion current density of ACC coated 316L steel was of the order of 10−7 A cm−2 in the simulated proton exchange membrane fuel cells (PEMFC) working environment, and the self-corrosion potential of the coating positively shifted by 0.4V, indicating a significant improvement on corrosion resistance of the coated steel plate due to excellent electrochemical stability of ACC. The Rockwell C indentation test showed that the as-obtained ACC was strongly bonded to the substrate and also had high in-plane strength. Further numerical simulation and comparison experiments showed that C was chemically bonded with Fe in the substrate, which was boosted by the assistance of NH 4 Cl. The intact and strong bonding between ACC and the substrate is highly helpful to improve corrosion resistance. The success in coating stainless steel plate with ACC by pulse electrodeposition method provides a promising alternation for coating of proton exchange membrane electrolyzer cell (PEMEC) and PEMFC metal bipolar plates. • Amorphous carbon coating (ACC) has prepared by electrodeposition on 316LSS. • The ACC was strongly bonded to the substrate and had high in-plane strength. • With the assistance of NH 4 Cl, C was chemically bonded with Fe in the substrate. [ABSTRACT FROM AUTHOR]

This study investigated Cu-doped a-C films prepared under a substrate bias gradually reducing from 120 to 60 V and different Cu target currents of 0, 0.15, 0.2, 0.3, 0.5 A, respectively, using closed field unbalanced magnetron sputtering physical vapour deposition technique. While the Cu-doped a-C film at the lowest Cu target current of 0.15 A (A0.15) remained an amorphous microstructure, Cu nanoprecipitates occurred at Cu target currents of 0.2–0.5 A. All the Cu-doped a-C films prepared exhibited good combination of corrosion resistance to a corrosive chemical mixture of 0.5 M H 2 SO 4 + 5 ppm HF (as suggested by the corrosion current densities) and interfacial electric conductivity (as demonstrated by the interfacial contact resistance, ICR). Among all coatings, A0.15 showed the best corrosion resistance and interfacial electric conductivity, which is attributable to the precipitate-free Cu-doped amorphous microstructure. The measured current density of A0.15 was 1.95 × 10−7 A/cm2 at 0.6 V (vs. SCE) during potentiodynamic polarization, which was lower than that of the Cu-free a-C film at 7.34 × 10−7 A/cm2. The ICR value of A0.15 was 4.40 mΩcm2 at an assembly pressure of 1.4 MPa, which is about one third of the Cu-free a-C film. This study demonstrates a new deposition strategy combining Cu-doping and the control of substrate bias to improve the corrosion resistance and interfacial electric conductivity of a-C films for PEMFC. [Display omitted] • A transition of microstructure from amorphous Cu solid solution to Cu-nanoprecipitation is observed. • The compactness and uniformity of a-C films can be enhanced due to Cu doping. • The film at the lowest Cu target current shows the best combination of corrosion resistance and interfacial conductivity. • A new deposition strategy combining Cu-doping and decreasing substrate bias is demonstrated. [ABSTRACT FROM AUTHOR]

Using a high-power impulse and direct current (DC) magnetron sputtering approach, C-doped CrN films with various C-target pulse frequencies are created on the surface of SS 304. The microstructure, corrosion resistance and conductivity of the films are examined. With the decreases of C-target pulse frequency, the roughness of the CrCN films decreases and the density increases. The results of XPS and TEM analyses demonstrate that C atoms are either present in CrN lattice as interstitial atoms or precipitate at grain boundaries to form amorphous carbon, which facilitates the increase of film density and conductivity. In the potentiodynamic tests, the CrCN-1000 Hz film exhibits the lowest corrosion current density 0.54 μA/cm2 at 0.6 V vs. Ag/AgCl potential. The values of i corr and E corr are 0.11 μA/cm2 and 0.427 V, respectively. Furthermore, the CrCN-1000 Hz film has the lowest interface contact resistance (ICR) under a compaction force of 140 N/cm2 after potentiostatic polarization test, indicating that C doping is beneficial to improve the corrosion resistance and conductivity of CrN film. • C-doped CrN films deposited on SS 304 by High Power Impulse Magnetron Sputtering. • C exists as interstitial atom in CrN lattice or amorphous C network at grain boundaries. • Formation of a-C or a-CN x at grain boundaries improve corrosion resistance of film. • Corrosion resistance and conductivity of C-doped CrN films superior to the DoE's criteria. [ABSTRACT FROM AUTHOR]

Abstract In here, we report on the pulse electrodeposition of nickel–chromium–phosphorous (Ni–Cr–P) coatings on AISI 1020 low carbon steel using an aqueous electrolyte consisting of NiCl2, CrCl3, and NaH2PO2. We evaluated the effectiveness of Ni–Cr–P coatings for polymer electrolyte membrane fuel cell metallic bipolar plates. Coatings deposited at pH 3.0 and room temperature show nearly three orders improvement in corrosion resistance compared to bare AISI 1020. The corrosion current (I corr) of Ni–Cr–P samples coated at 25 °C is 1.16 × 10−4 A/cm2, while that of bare carbon steel is 1.05 × 10−2 A/cm2. The improvement in corrosion resistance is due to the increase in Cr content in the Ni–Cr–P coatings. Cr forms a stable oxide barrier layer and inhibits pitting corrosion. The interfacial contact resistance increases with an increase in Cr content and immersion time in the corrosion media. The increase in interfacial contact resistance is also due to the formation of a stable oxide barrier.

Polypropylene (PP) nanocomposites with multi-walled carbon nanotubes (MWCNT) alone or combined with carbon nanofibers (CNF) at different loadings have been fabricated by melt mixing with a focus on their mechanical properties and corrosion resistance for bipolar plates applications in proton exchange membrane fuel cells (PEMFCs). The incorporation of up to 20 wt% MWCNT in the PP matrix produces enhancements of 71, 47, 56, and 30% in microhardness, elastic modulus, and tensile and flexural strength, respectively. Combined additions of MWCNT and CNF allow producing hybrid nanocomposites with increased strength than when neat MWCNT as reinforcement, preserving their processability even at a total filler content of up to 30 wt%. The measured values of i corr in both PP/MWCNT and PP/MWCNT/CNF suggest a slow degradation rate in the PEMFC environment. Based on the US Department of Energy (DOE) targets, PP/20MWCNT, PP/21.5MWCNT, and PP/15MWCNT/15CNF nanocomposites are good candidates to produce bipolar plates for PEMFCs. [Display omitted] • PP/MWCNT and PP/MWCNT/CNF blends are evaluated for potential use in bipolar plates. • Hybrid composites reach 45.3 MPa in flexural strength and 0.046 μA cm−2 in i corr. • PP/MWCNT/CNF blends meet most of the targets set by the US DOE for bipolar plates. [ABSTRACT FROM AUTHOR]

Proton exchange membrane water electrolysis (PEMWE) is a promising technology to be incorporated in the production of green hydrogen, but one of its limitation to market penetration is the cost of bipolar plates (BPP). Aiming to reduce the cost of PEMWE stack, different surface engineered coating systems based on CrN/TiN, Ti/TiN, Ti and TiN deposited by physical vapor deposition on SS 316L, SS 904L and SS 321 were tested, as potential cost effective solutions to be implemented on bipolar plates. A corrosion evaluation has been carried out in anodic PEMWE conditions in order to determine the best substrate/coating combination for bipolar plates. Ti/TiN multi-layered coating on SS 321 shown the best performance with −0.02% weight loss, current at 2 V SHE to 436 μA cm−2 and ICR after corrosion test to 9.9 mΩ cm2. • Corrosion resistance of titanium coatings on different stainless steel were evaluated. • Stainless steel 321, 316L and 904L were evaluated such coatings substrates. • Operating conditions of PEMWE anode site were simulated in a three-electrode corrosion cell. • The ICR was measurement by the Davis method modified for electrolysis cells. • PVD Ti/TiN multilayers deposited on SS321 show no morphological changes or loss of coating in corrosion test. [ABSTRACT FROM AUTHOR]

The unique chemical and physical properties of graphene and its derivatives (graphene oxide, heteroatom‐doped graphene, and functionalized graphene) have stimulated tremendous efforts and made significant progress in fuel cell applications. This review focuses on the latest advances in the use of graphene‐based materials in electrodes, electrolytes, and bipolar plates for fuel cells. The understanding of structure‐activity relationships of metal‐free heteroatom‐doped graphene and graphene‐supported catalysts was highlighted. The performances and advantages of graphene‐based materials in membranes and bipolar plates were summarized. We also outlined the challenges and perspectives in using graphene‐based materials for fuel cell applications. [ABSTRACT FROM AUTHOR]

The field of proton exchange membrane fuel cells (PEMFCs) has been of primary interest in transportation applications as a result of their low pollutant emissions and relatively high efficiency. Bipolar plates are the vital components of these devices and are often exposed to corrosive environments due to their operational processes. Potentiodynamic polarization is used by researchers to investigate the material behavior of BPP used in the PEMFC applications. This paper aims to describe the application of electrochemical analysis in understanding the material behavior of PEMFC components, with a particular focus on the utilization of potentiodynamic polarization to provide material degradation information of bipolar plates. The potentiodynamic polarization test examines the material behavior of BPPs in terms of using voltage and current density change. This paper, therefore, combined potential applications of potentiodynamic polarization analysis technique to explore the BPP material behavior in two different PEMFC applications of start-up and shut-down processes. [ABSTRACT FROM AUTHOR]

Stainless steel fulfills most of the requirements as bipolar plates in Proton Exchange Membrane Fuel Cell. However, it undergoes severe corrosion in fuel cell operating condition. This can be resolved by coating the stainless steel with corrosion resistive conducting polymers. In this study, homogeneous and adherent conductive Poly(2-amino-5-mercapto-1,3,4- thiadiazole)/Polypyrrole (PAMT/PPY) mono and bilayer polymer composite coatings are electrosynthesized on 316L SS in 0.5 M H 2 SO 4 by cyclic voltammetry and chronopotentiometry. The hydrophobicity and surface morphology of the coatings are analyzed by contact angle and scanning electron microscopy respectively. The polymer coatings are evaluated in 0.5 M H 2 SO 4 medium by potentiodynamic polarization and impedance techniques at 25 °C. The polarization results reveal that PAMT on PPY composite coating shifts the E corr of the 316L SS towards noble direction. The EIS study reveals that the R f value of PAMT on PPY coating is significantly higher by three orders (x103 Ωcm2) of magnitude than uncoated 316L SS. The corrosion performance of the coatings in simulated PEMFC environment is investigated by potentiodynamic and potentiostatic studies. Results show that the PAMT on PPY and PPY on PAMT bilayer coatings are stable and increased the corrosion potential by about 410–470 mV and 275–310 mV (SCE) in simulated cathodic and anodic conditions respectively. This investigation reports that the PAMT on PPY bilayer coating is serving as a good physical barrier and protecting the 316L SS against corrosion in PEMFC environment. • PAMT/PPY mono and bilayer composite coatings are electropolymerized on 316L SS. • The coatings enhance E corr and decrease Corrosion rate of 316L SS in simulated PEMFCs. • Bilayer coatings exhibit better hydrophobicity and protection than monolayer. • The dense compact PAMT on PPY bilayer coating serves as a good physical barrier. [ABSTRACT FROM AUTHOR]

As promising materials for bipolar plates substrate, as-cold rolled Ti-0.3Ni (wt.%) sheets were heat treated with three different processes in this work. As-cold rolled sheets consist of α matrix and dispersed Ti2Ni intermetallic precipitates, and typical Widmanstatten microstructure can be observed after heat treatment. Lamellar Ti2Ni precipitates inside the colonies. Elongation of as-cold rolled sheets equals less than 7% while this value rises up to around 20%, and tensile strength decreases by more than 47% after heat treatment. Open circuit potentials of as-cold rolled sheets treated at 950 °C for 1 h followed by wind cooling (950 °C/1 h/WC), sheets aged at 500 °C for 3 h followed by air cooling (950 °C/1 h/WC + 500 °C/3 h/AC), and sheets treated at 950 °C for 1 h followed by furnace cooling (950 °C/1 h/FC) equals −0.536 V, −0.476 V, −0.486 V, −0.518 V, respectively. A potentiodynamic polarization test reveals that all of the specimens exhibit typical active–passive transition behavior. Sheets treated at 950 °C/1 h/WC possess the lowest corrosion current density (155.4 μA·cm−2). Results of electrochemical impedance spectroscopy (EIS) show that 950 °C/1 h/WC treated sheets possess the largest polarization resistance (Rpol), 122.6 Ω·cm2. Moreover, steady-state current densities (Iss) increase in the order of 950 °C/1 h/WC, 950 °C/1 h/WC + 500 °C/3 h/AC, 950 °C/1 h/FC according to the results of potentiostatic polarization. This can be attributed to various amounts of Ti2Ni precipitation caused by different cooling rates.

Trace-metal contamination poses a threat to performance and stability of proton exchange membrane fuel cells (PEMFCs). In this study the source of origin and degree of metal dissolution from carbon-coated 316L bipolar plates (BPPs) are evaluated after a long-term PEMFC test run under conditions resembling a real-life automotive application. Despite intact carbon-coating, metal dissolution occurs from uncoated oxycarbide stains on the plates' surface. Which correlates with post-mortem detection of chromium, iron and nickel in the membrane electrode assembly. The rate of cell voltage decrease throughout the high current operations is found to be twice as high in the presence of metal ions. Metal dissolution can be correlated with transients in cell voltage during dynamic current load cycling as a result of temporary global fuel starvation. The observed difference in metal dissolution on the anode and cathode BPP indicates weak galvanic coupling between the bipolar plate(s) and the electrode layer(s). • Simultaneous in situ measurement of cell voltage and interfacial contact resistance. • Source of metal contamination were uncoated metal oxycarbide stains on bipolar plates. • Metal dissolution was correlated with voltage transients caused by fuel starvation. • Asymmetric dissolution indicates galvanic decoupling between plates and electrodes. [ABSTRACT FROM AUTHOR]

The performance and durability of proton exchange fuel cells (PEMFCs) are greatly affected by the bipolar plate (BP). In this paper, the thermal and electrical conductivities and mechanical property of graphite filled with resin composite BPs were collectively enhanced through the effectively coupled manipulations of molding pressure and impregnation pressure. The microstructures show that the resin tends to distribute at the top region of the rib under high impregnation pressure. The thermal and electrical conductivities of the pure expanded graphite BP is well reserved in the composite BPs under high molding pressure, which can facilitate the heat transfer and electron conduction in the PEMFCs. The relative density and compressive strength of composite BPs were greatly enhanced by the impregnation of resin compared to the expanded graphite under high molding pressure without the impregnation of resin (HU-BP). The maximum thermal conductivity, compressive strength, and minimum interfacial contact resistance (ICR) are collectively achieved in the HL-BP. The enhanced thermal-electrical and mechanical properties could be mainly attributed to the well-reserved continuous networks of graphite in the composite BPs. The findings in this paper are expected to synergetically improve the thermal, electrical, and mechanical properties of composite BPs through coupled manipulations of the molding and impregnation pressures, which in turn enhances the power density and durability of PEMFCs.

Bipolar plates (BPs) are key components of Proton Exchange Membrane Fuel Cells mainly employed in hydrogen-powered electric vehicles. Here, a reliable and detailed experimental method to prepare graphite-epoxy composites suitable for manufacturing BPs is reported. Dry and wet mixing procedures were compared and a simple composition was optimized, with regard to electrical conductivity. The adoption of wet mixing of the components and the choice of the conductive filler were the main factors that contributed to the achievement of good electrical and mechanical properties. The addition of a small percentage of carbon black as a secondary filler was also advantageous. The effects of molding parameters (pressure, temperature and time) on a fixed-composition graphite-epoxy composite were modeled using a Design Of Experiments approach, which provided valuable information for future improvements. Conductivity values well above the US DOE requirements were obtained. • Bipolar plates with conductivity above US DOE were obtained from low cost materials. • When an epoxy binder is used, processed graphite is preferred over natural graphite. • Preparation by wet mixing is preferred over dry mixing the composite components. • Design of Experiment gave useful hints for future improvements. [ABSTRACT FROM AUTHOR]

A single cell of direct methanol fuel cell (DMFC) typically delivers an electrical potential between 0.5 and 1 V; thus DMFCs are assembled in parallel to meet power demands (1–5 kW). Bipolar plates (BPs) are the primary components connecting a single cell to the adjacent cells so that they provide optimum electrical conductivity. The objective of this research is to reduce the volume resistance of BPs made from a polypropylene/carbon composite by utilizing a metal insert technique. A major obstacle when it comes to molding composite plates inserted by a thin metal sheet is the delamination of material layers after the cooling process. The delamination issue is due to different surface polarities between metal and polypropylene-composite surfaces. One of the strategies to solve this issue is to modify the surface of one layer for creating similarity of the surface polarity. A metal sheet surface was coated with graphene using a cold spraying technique to enhance adhesion ability. The suitable spraying conditions were determined by experimenting with varying temperature, pressure, graphene quantity and graphene types. The effectiveness of surface modification by the graphene spraying technique was assessed by a surface morphology observation, an electrical conductivity measurement and DMFC performance tests. Results were interesting, they indicated that when DMFC was assembled with silver sheet, inserted BPs provided 25.13 mW/cm2 of power density, 3,350.7 mWh of generated energy and 67% of efficiency. This highlights that the performance of a BP prototype is superior to the performance of a commercial composite bipolar plate. [ABSTRACT FROM AUTHOR]

Bipolar Plates (BPP) are important components of proton exchange membrane fuel cell (PEMFC) stacks. In the development of innovative fuel cell designs, it is advantageous to use aluminum for these applications, however, this material lacks the necessary corrosion resistance. Since the performance of PEMFC stacks depends on BPP properties, in particular, corrosion resistance, depositing titanium nitride (TiN) thin films onto aluminum substrates may improve their efficiency and durability. The present work focuses on improving corrosion resistance and hydrophobicity of TiN/Ti by using N graded films deposited onto aluminum substrates (AA-1100) by grid-assisted magnetron sputtering (GAMS). Electrochemical impedance spectroscopy (EIS) and potentiodynamic and potentiostatic polarization are used to investigate the performance of the substrate/film system at room temperature and 70 °C, thus simulating a prototypic PEMFC electrolyte environment. Electrochemical test results showed that graded TiN films improved corrosion resistance when compared with both the homogeneous films and the AA1100 uncoated substrate. Furthermore, contact angle results reveal improved hydrophobicity for both homogeneous and graded TiN coatings when compared with the AA1100 substrate. • Graded and homogeneous TiN/Ti films were deposited on AA-1100 substrates by GAMS. • TiN/Ti films shows better corrosion resistance than the uncoated substrate. • Contact angle results of TiN/Ti films was greater than substrates uncoated. • Graded TiN/Ti films outperforms the corrosion resistance of homogeneous TiN/Ti films. • Graded TiN/Ti films can be successfully applied to bipolar plates surface. [ABSTRACT FROM AUTHOR]

This research aims to develop polybenzoxazine (PBA) based composites suitable for bipolar plates in proton exchange membrane fuel cells (PEMFCs). PBA composites filled with carbon derivatives i.e. graphite, graphene, and multiwall carbon nanotubes (CNTs) were prepared. The effects of CNT contents from 0–2 wt% at an expense of graphite with constant content of graphene and benzoxazine on properties of the obtained composites were investigated. It was found that the composite with 2 wt% of CNTs exhibited through-plane thermal conductivity as high as 21.3 W/mK which is 44 times higher than that of the composite without CNTs. Also, this composite showed electrical conductivity of 364 S/cm, Flexural Strength of 41.5 MPa and Modulus 49.7 GPa, respectively. These values meet the requirements suggested by the Department of Energy, USA and confirm that these composites are great candidates as bipolar plates for PEMFCs. Image 1 • Bipolar plate based on graphite/graphene/CNT filled in PBA is developed. • The properties of the composites were improved with an addition of CNT. • Thermal conductivity of the composite having 2 wt% of CNT was as high as 21.3 W/mK. • The relevant properties of the composite met those requirements by DOE. [ABSTRACT FROM AUTHOR]

A titanium bipolar plate for fuel cell not only has excellent corrosion resistance but also has a lower density than stainless steel bipolar plates. However, titanium exhibits low formability at room temperature that requires warm forming as a prominent solution to overcome this drawback. The present study investigates the forming of bipolar plates for the proton exchange membrane fuel cell out of commercially pure titanium ultra-thin sheet. In this regard, the formability of the titanium sheet with a thickness of 0.1 mm was first evaluated through the tensile test at different deformation temperatures and speeds. Also, V-die bending experiments were carried out at room and warm temperatures to examine springback of the sheet. Afterward, a warm stamping setup was conducted to fabricate the titanium bipolar plates in the range from room temperature to 200 °C with stamping speed varying between 0.6 and 4.8 mm/min. Accordingly, the formed samples were analyzed and their forming rate, thinning rate, and springback were discussed. The results indicated that the formability of the titanium sheet depends on both forming temperature and speed. The most elongation of the sheet was obtained at a temperature of 100 °C and a deformation speed of 0.6 mm/min. The maximum channel depth was obtained equal to 0.494 mm using a warm stamping process that implies an improvement by 40% in the filling rate of microchannels compared with forming at the room temperature. Likewise, the dimensional error of the titanium bipolar plate due to the springback was decreased by stamping at 100 °C compared with forming at room temperature. [ABSTRACT FROM AUTHOR]

During actual vehicle applications, the condition of start-up/shut-down generates high cathodic potential, causing the anodic dissolution and having a great impact on the lifetime of proton exchange membrane fuel cell (PEMFC). In order to improve the durability of the bipolar plate at high potential, the present work investigated the oxygen-doped TiN coating deposited on the surface of SS316L matrix. The results of X-ray photoelectron spectroscopy and X-ray diffraction showed that TiNO and TiO 2 existed in oxygen-doped coatings. The surface morphology analysis indicated that the oxygen-doped coatings tended to come into being denser surface. Besides, the tested results of potentiodynamic polarization, triangle wave high potential cyclic polarization, the electrochemical impedance spectrum and water contact angle test revealed that the TiNO-7sccm specimen possessed the best corrosion resistance, durability and surface hydrophobicity. After a long-term polarization (+0.6 V SCE), the TiNO-5sccm samples possessed the lowest interfacial contact resistance value of 19.8 mΩ cm2. Image 1 • A controlled amount of oxygen is incorporated into TiN by CFUMSIP. • TiNO coatings improves resistance of BPPs to high potential corrosion. • TiNO combines the high corrosion resistance of TiO 2 and high conductivity of TiN. • TiNO possess lower ICR and corrosion current density than TiN after the long-term polarization. [ABSTRACT FROM AUTHOR]

Metallic bipolar plates (BPPs) are potential candidates to replace the conventional graphite BPPs in polymer electrolyte membrane fuel cells (PEMFCs) because they are cost-effective and easy to manufacture. In this present work, we report on the development of Ni–Mo–Cr–P electroplated AISI 1020 steel bipolar plates as a BPP material. The microstructure and composition of the Ni–Mo–Cr–P coatings were optimized varying pH of the electrolyte bath and deposition current. Compared to bare AISI 1020 steel, the coating electroplated at pH 5.5 and a pulse-current density of 0.075 A/cm2 showed an improvement in corrosion resistance by three orders of magnitude. The corrosion current densities of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel in the simulated anodic environment is 1.05 × 10−2 and 4.95 × 10−5 A/cm2, respectively, while that in the simulated cathodic environment it is 3.7 × 10−2 and 4.58 × 10−5 A/cm2, respectively. The enhancement of corrosion resistance is due to the formation of a Mo and Cr based passive oxide layer. The interfacial contact resistance (ICR) of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel is 53.2 and 40.06 mΩ, respectively. ICR of Ni–Mo–Cr–P is lower than the bare AISI 1020 because of the semiconducting nature of the two-layered Mo-based passive oxides. Additionally, Ni–Mo–Cr–P coated AISI 1020 steel shows a higher water contact angle than bare AISI 1020 carbon steel. A single-cell PEMFC stack with Ni–Mo–Cr–P coated AISI 1020 steel BPP shows similar polarization behavior as graphite BPP. However, the performance of Ni–Mo–Cr–P coated AISI 1020 steel BPP lacks durability, and further improvement is necessary before it can be commercially implemented. Image 1 • Dense quaternary amorphous Ni–Mo–Cr–P coatings electrodeposited on AISI 1020 steel. • Ni–Mo–Cr–P coatings show lower ICR and higher corrosion resistance than bare steel. • Coating improved the hydrophobicity of the AISI 1020 steel. • Better power density observed with coated BPPs compared to bare AISI 1020 BPPs. [ABSTRACT FROM AUTHOR]

In the present research, the corrosion resistance of Ni–P and Ni–P–Cr coatings on AA7075-T6 aluminum plates under simulated anodic and cathodic conditions of polymer electrolyte membrane fuel cells (PEMFC) has been studied by electrochemical impedance spectroscopy (EIS). Three Ni–P coatings 20 μm, 30 μm, and 40 μm thick applied by electroless deposition were tested. Besides, a two-layer Ni–P–Cr coating 30 μm thick was also analyzed. It was formed by an inner Ni–P layer, and an outer 10 μm thick chromium one added by electroplating. Corrosion tests were combined with interfacial contact resistance (ICR), roughness, contact angle, and SEM-EDX measurements. The best results were obtained for the 20 μm Ni–P and the two-layer Ni–P–Cr coatings, although the latter showed a high ICR value due to the high electrical resistivity of the chromium oxide surface formed. It was verified that coating degradation occurs when the electrolyte penetrates the micro-cracks and the nodular surface interfaces, reaching the base metal and causing the coating delamination. This behavior is associated with a sharp decrease in the polarization resistance (R p) of the equivalent circuit model fitted to the EIS results. • The thickness of Ni–P coatings on Al AA7075-T6 substrates has been optimized. • The best results were obtained for the Ni–P 20 μm thick and the Ni–P–Cr 30 μm coatings. • DRT analysis of the EIS spectra allows to obtain consistent physical models of Ni–P–Cr coatings. • The proposed equivalent circuit model predicts the durability of the coatings. • Coating surface morphology is a very important factor in the corrosion process. [ABSTRACT FROM AUTHOR]

Austenitic stainless steels (ASSs) offer many advantages over carbon and/or graphite composites for bipolar plates of proton exchange membrane fuel cells (PEMFCs). However, its corrosion resistance in PEMFCs operating conditions is lower. A low temperature (450°C) salt bath nitriding technique for different durations (3, 6 and 12 h) was employed to modify the surface of 316L ASS to enhance its corrosion resistance. The scanning electron microscopy of the transverse sections of nitrided sample reveals a white layer and its thickness increases on increasing nitriding durations. The X-ray photon spectroscopy results show that on nitriding, nitrogen (N) is present in the free form (on 3 h duration) and nitrides (CrN and FexN) precipitates (on 6 and 12 h durations). The corrosion resistance increased on nitridation. The best corrosion resistance was obtained for 3 h nitriding. The corrosion resistance decreases on increasing durations which can be attributed to the formation of nitrides. [ABSTRACT FROM AUTHOR]

An easily machined novel flow field with controllable pressure gradient across adjacent channels was designed and a two dimensional, across‐the‐channel, two‐phase model was developed to study the gas transport and water removal of the novel configuration. The effect of channel‐rib width ratio, GDL thickness and pressure gradient on the profiles of oxygen concentration and water saturation within the GDL were investigated. Special attention was paid to the mechanisms of the promoted mass transport and water removal rates under a pressure gradient. The model was validated by experiments with various channel‐rib ratios and GDL thicknesses at different operating pressure. The results revealed that, oxygen concentration was increased, and the water saturation was reduced under the rib with a pressure gradient generated across the adjacent channels. The optimal pressure gradient is between 0.1 to 0.2 atm for the studied channel geometry and configuration. The mechanisms of the improved cell performance were elucidated. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) generate electricity utilizing the energy of electrochemical reactions of fuel (H2) and oxidants (O2/air). As they emit no toxic gases during the process, they are considered as a clean energy source that can be beneficial and might replace the use of fossil fuels. To compose a FC stack, an essential component, bipolar plates (BPs), is needed. They have several roles to fulfill during PEMFC stack operation, and there are many challenges when it comes to BPs metal‐based materials and their sustainability, durability, and longevity. Finding suitable metal and alloy materials is a significant task as BP materials should have multiple qualities that sometimes come at the expense of one another. As BPs constitute a significant part of PEMFC stack by means of volume, weight, and costs, the pursuit of the most suitable and least expensive metal‐based materials is comprehensible. In this Review, different metal and alloy types (copper, nickel, titanium, and aluminum alloys) and their own particular challenges are discussed, emphasizing the most important family of materials candidates—stainless steels. [ABSTRACT FROM AUTHOR]

Impact of graphite on the physicochemical properties of high density polyethylene (HDPE)/copper composites has been investigated at various volume percentages of copper. The two sets of composites are prepared by simple melt blending and injection molding approach. Thermal conductivity increases from 0.5 W m−1 K−1 for pure HDPE to 6.5 and 8 Wm−1 K−1 for 30 and 40 vol.% of copper loading with and without graphite, respectively. A huge increment in synergistic efficiency has been evidenced for the mixed filled polymer composites. Incorporation of graphite has also improved the percolation threshold from 19 to 13 vol.% of copper loading to the HDPE matrix, which indicates the synergistic effect of mixed filler system. Development of leafy morphology of copper promotes large number of inter‐particle contacts and hence improves the percolation threshold of the composites. The corrosion resistive, mechanically robust, electrically and thermally conductive composites with good flexural properties and light in weight than conventional metallic bipolar plates suggest it a material of choice for fuel cell devices. [ABSTRACT FROM AUTHOR]

• The a-C/(Ti:C)/Ti film with 300 nm thickness prepared by multi-arc ion plating. • Improved 316L stainless steel corrosion resistance in simulated cathode solution. • Current density reaches 0.076 μA·cm−2 after 4 h test at 0.6 V (vs. Ag/AgCl). • Low interfacial contact resistance and hydrophobicity for a-C/(Ti:C)/Ti film. To enhance corrosion resistance and electrical conductivity of metallic bipolar plates for proton exchange membrane fuel cells (PEMFCs), the film containing amorphous carbon (a-C) outer layer, titanium carbon compound (Ti:C) transition layer and titanium (Ti) seed layer has been deposited on the surface of 316L stainless steel (316L SS) by multi-arc ion plating method. Dense and uniform a-C/(Ti:C)/Ti nano-thin film is relatively hydrophobic and approximately 300 nm thick, presenting a clear multilayer structure. The interfacial contact resistance of 316L SS is effectively reduced from 124.97 mΩ·cm2 to 3.97 mΩ·cm2 at 1.4 MPa after modification. Electrochemical corrosion tests are investigated in the simulated cathodic PEMFCs environment (0.5 M H 2 SO 4 and 2 ppm HF at 70 ℃ bubbled with air). Potentiodynamic polarization results reveal that the corrosion potential of a-C/(Ti:C)/Ti film modified sample is 0.23 V (vs. Ag/AgCl) and the corrosion current density is only 0.14 μA·cm−2. The durability of the a-C/(Ti:C)/Ti film was assessed by conducting potentiostatic polarization tests at various applied potentials. After 4 h potential of 0.6 V and 0.8 V (vs. Ag/AgCl) holding tests, the current densities of the modified 316L SS have stabilized at 0.076 μA·cm−2 and 0.098 μA·cm−2, respectively. [ABSTRACT FROM AUTHOR]

• Ti-Nb-Ni foils possess nice corrosion resistance in 0.5 M H 2 SO 4 with 5 ppm F- at 80℃. • Ni-rich layer formed during foil preparing efficiently improves corrosion resistance. • Interfacial contact resistance of Ti-Nb-Ni foil is lower than 10 mΩ·cm2. In this work, corrosion behavior of Ti-Nb-Ni foil in 0.5 M H 2 SO 4 solution containing different fluoride concentrations at various temperatures was investigated by electrochemical measurements, X-ray photoelectron spectroscopy and scanning electron microscopy. Corrosion resistance of specimens degraded with temperature and fluoride concentration increasing judged by more negative open circuit potential, larger corrosion current density as well as reducing polarization resistance. The critical fluoride concentrations were in the range of 100 ∼ 200 ppm for 20℃ and 50 ∼ 100 ppm for 40℃ to 80℃, above which passive film was destroyed causing contact between substrate and solution. While in the cases of fluoride concentrations lower than critical value, passivation of foil was retained. Furthermore, a nickel-rich layer was found via X-ray photoelectron spectroscopy analyses and thickness of the layer descended with fluoride concentration and temperature increasing. Interfacial contact resistance of the foils after being potentiostatically polarized at 0.6 V for 6 h at 80℃ were lower than 10 mΩ·cm−2, meeting the requirement of Department of Energy (DOE) and interfacial contact resistance increased by different degrees with fluoride concentrations. [ABSTRACT FROM AUTHOR]

In this study, the corrosion behavior of Ta and TiN double-layered-coated SUS316L is investigated for proton-exchange membrane fuel cells (PEMFCs) bipolar plates. The surface of SUS316L is modified by depositing 4.5 µm of Ta and 200 or 400 nm of TiN using magnetron sputtering and plasma-enhanced atomic layer deposition, respectively. The experimental results reveal that this coating significantly enhances the corrosion resistance and reduces the interfacial contact resistance of the bipolar plate. Under electrochemical conditions that are 500 times more acidic than those specified by the Department of Energy (DOE), the coated SUS316L achieves a corrosion current density of only 1.0 µA/cm2 at 0.6 V SCE. The corrosion current density reduces up to more than two orders of magnitude, and the interfacial contact resistance with carbon paper is below 10 mΩcm2 at compression forces below 140 N/cm2, thus meeting the DOE 2025 target value for both corrosion current density and interfacial contact resistance. Our findings suggest the potential of Ta and TiN double-layered-coated SUS316L as durable bipolar plate materials for PEMFCs. • Double layered structure protection layer was fabricated via Sputtering and PEALD. • Corrosion current density was significantly enhanced, reaching 1.0 μA/cm² at 0.6 V vssce and 80 °C in 0.5 M H 2 SO 4. • Interfacial contact resistance with carbon paper improved from 212 mΩcm2 to 7.75 mΩcm2 at 150 N/cm2 compression force. • The corrosion current density and ICR value satisfied the DOE target values for PEMFC bipolar plate. [ABSTRACT FROM AUTHOR]

This study comprehensively investigates the electrochemical and passive behaviors of Pt-coated commercially pure titanium (CP-Ti), with a specific focus on the influence of preparation power. The research highlights a positive correlation between coating grain size and the preparation power. Furthermore, the Pt coating proves effective in impeding CP-Ti passivation and exhibits a weak influence on the energy barrier height with changing electrode potential. Among different power levels, the coating prepared at 300 W exhibits the highest corrosion resistance, as evidenced by the maximum R ct value of 8.971 × 104 Ω cm2. The predominance of metallic Pt accounts for minimal variation in interfacial contact resistances. Moreover, Pt coating effectively reduces cell resistance and protects bipolar plates, though it falls short in effectively alleviating the degradation. [Display omitted] • The coating grain size is positively correlated to the preparation power. • Pt coating can effectively hinder the passivation of CP-Ti. • The coating prepared at 300 W exhibited the highest corrosion resistance. • The dominance of metallic Pt accounts for the minimal variation in ICRs. • Pt coating is insufficient to effectively reduce single cell degradation. [ABSTRACT FROM AUTHOR]

The Ni57Nb33Zr5Co5 metallic glass is a promising alloy for bipolar plates in proton exchange membrane fuel cells. It is important to know which phase forms in this alloy under different cooling rates in order to understand its influence on the thermal stability and mechanical properties. In this work, melt-spun ribbons and rod samples with 1, 2 and 3 mm diameters were prepared and their phase formation, microstructure and mechanical properties were investigated by X-ray diffraction, differential scanning calorimetry, optical microscopy, scanning electron microscopy and microhardness. It is found that a completely crystalline structure forms in the lower cooling rate samples (2 and 3 mm diameter rods) with the presence of the equilibrium phases Ni3(Nb,Zr) and Nb7Ni6 as primary phases or as a very fine eutectic structure, while a fully glassy structure is attained in the samples with the highest cooling rate (ribbons). For the sample with an intermediate cooling rate (1 mm diameter rod), polymorphically crystals of an unknown metastable phase with spherical morphology precipitate in the glassy matrix with virtually the same composition as the matrix. The 2 mm diameter sample exhibits higher hardness than the other samples, which is attributed to its very fine eutectic colonies.

Fuel cells rely on an effective distribution of the reactant gases and removal of the byproduct, that is, water. In this context, bipolar plates are the critical component for the effective management of these fluids, as these dictate to some extent the overall performance of polymer electrolyte membrane fuel cells (PEMFCs). Better bipolar plates can lead to a significant reduction in size, cost, and weight of fuel cells. Herein, we report on the use of photoresin 3D printing to fabricate alternative bipolar plates for operating self-breathing fuel cell stacks. The resulting stack made of 12 self-breathing PEMFCs achieved a power density of 0.3 W/cm 2 under ambient conditions (25°C and 20% relative humidity), which is superior to the performance of previously reported self-breathing cells. The problems associated with hydrogen leaks and water flooding could be resolved by taking advantage of 3D printing to precisely fabricate monoblock shapes. The approach of 3D printing reported in this study demonstrates a new path in fuel cell manufacturing for small and portable applications where an important reduction in size and cost is important., Competing Interests: No competing financial interests exist., (Copyright 2024, Mary Ann Liebert, Inc., publishers.)

The electrochemical properties and interfacial contact resistance (ICR) of four Zr-based bulk metallic glasses with different compositions are evaluated for PEMFC applications. Based on the results and market demands, the corrosion behavior of the Zr 41·2 Ti 13·8 Cu 12·5 Ni 10 Be 22.5 (numbers indicate at.%) BMG and 304 stainless steel (SS304) in accelerated simulated anode and cathode environments, such as 0.5 M H 2 SO 4 and 2 ppm HF solutions bubbled with pure hydrogen and air at 80 °C, respectively, is further investigated through potentiodynamic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy. The performance tests of the single cell with the Zr-based BMG as BPPs are conducted and the maximum power density of the single cell has exceeded 470 mW/cm2. The combination of these results and other properties demonstrate that the Zr-based BMG can be used as the anode or cathode material for metallic bipolar plates. Image 1 • Electrochemical corrosion and ICR of Zr-based BMGs with different compositions are investigated. • The maximum power density of the single cell with the Zr-based BMG as BPPs has exceeded 470 mW/cm2. • Zr-based BMG is a potential anode or cathode material for BPPs. [ABSTRACT FROM AUTHOR]

Insufficient corrosion resistance, electrical conductivity and wettability of bipolar plates are some of the important issues affecting the performance of hydrogen fuel cells. To address these issues, an amorphous Al–Cr–Mo–N coating is deposited on type 316L stainless steel using direct current (DC) magnetron sputtering. The electrochemical corrosion behaviour is investigated under simulated fuel cell anode (H 2 -purging) and cathode (air-purging) environment consisting of 0.5 M H 2 SO 4 + 2 ppm NaF at 70 ± 2 °C. The corrosion current density is reduced to 0.02 μA cm−2 comparable to the commercially used Ta/TaN coatings. The polarization resistance increases by two orders of magnitude and the interfacial contact resistance (ICR) reduces significantly due to the application of the coating. Further, the coating shows better water management due to high hydrophobicity than the bare stainless steel. • Amorphous Al–25Cr–5Mo–40N alloy coating is developed on type 316L SS. • Corrosion resistance of the present coating is comparable to Ta/TaN coating. • ICR of the coating is significantly lower than that of the bare substrate. • High hydrophobicity of the coating can lower water flooding within PEMFC stacks. [ABSTRACT FROM AUTHOR]

The most important issues that plague wider use of polymer electrolyte membrane fuel cells (PEMFCs) are insufficient corrosion resistance, electrical conductivity and wettability of metallic bipolar plates (BPPs). To address these issues, an amorphous Al‐Cr‐Mo ternary alloy coating is applied on type 316L stainless steel using direct current magnetron sputtering. The electrochemical corrosion behavior of bare and alloy coated specimens has been investigated by polarization and electrochemical impedance spectroscopy techniques under simulated fuel cell working environment consisting of 0.5M H2SO4 at 70 ± 2 °C. The results indicate that the corrosion current density of the alloy coated specimen is approximately 0.2 µA cm−2 showing a reduction of two orders of magnitude. The polarization resistance increased by an order of magnitude and the interfacial contact resistance (ICR) is reduced significantly (45 and 48 mΩ cm2 in the simulated anode and cathode environments, respectively) due to the application of the coating. The chromium and molybdenum enrichment on the surface of coated specimen, as revealed by X‐ray photoelectron spectroscopy, is proposed to be responsible for the improved corrosion resistance. Further, the coating is expected to show significantly better water management due to high hydrophobicity than the bare stainless steel. [ABSTRACT FROM AUTHOR]