Comparative review of corrosion-resistant coatings on metal bipolar plates of proton exchange membrane fuel cells

In the realm of proton exchange membrane fuel cells(PEMFCs),the bipolar plates(BPs)are indispensable and serve pivotal roles in distributing reactant gases,collecting current,facilitating product water removal,and cooling the stack.Metal BPs,characterized by outstanding manufacturability,cost-effectiveness,higher power density,and mechanical strength,are emerging as viable alternatives to traditional graphite BPs.The foremost challenge for metal BPs lies in enhancing their corrosion resistance and conductivity under acidic conditions,necessitating the application of various coatings on their surfaces to ensure superior performance.This review summarizes and compares recent advancements in the research of eight distinct types of coatings for BPs in PEMFCs,including noble metal,carbide,ni-tride,and amorphous carbon(a-C)/metal compound composite coatings.The various challenges encountered in the manufacturing and fu-ture application of these coatings are also delineated.

Ti/(Ti,Cr)N/CrN multilayer coated 316L stainless steel by arc ion plating as bipolar plates for proton exchange membrane fuel cells

Arc ion plating (AIP) is applied to form Ti/(Ti,Cr)N/CrN multilayer coating on the surface of 316L stainless steel (SS316L) as bipolar plates for proton exchange membrane fuel cells (PEMFCs). The characterizations of the coating are analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Interfacial contact resistance (ICR) between the coated sample and carbon paper is 4.9 m Omega cm(2) under 150 N/cm(2), which is much lower than that of the SS316L substrate. Potentiodynamic and potentiostatic tests are performed in the simulated PEMFC working conditions to investigate the corrosion behaviors of the coated sample. Superior anticorrosion performance is observed for the coated sample, whose corrosion current density is 0.12 mu A/cm(2). Surface morphology results after corrosion tests indicate that the substrate is well protected by the multilayer coating. Performances of the single cell with the multilayer coated SS316L bipolar plate are improved significantly compared with that of the cell with the uncoated SS316L bipolar plate, presenting a great potential for PEMFC application. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Process and challenges of stainless steel based bipolar plates for proton exchange membrane fuel cells

Proton exchange membrane fuel cell(PEMFC)powered automobiles have been recognized to be the ultimate solution to replace traditional fuel automobiles because of their advantages of PEMFCs such as no pollution,low temperature start-up,high energy density,and low noise.As one of the core components,the bipolar plates(BPs)play an important role in the PEMFC stack.Traditional graphite BPs and composite BPs have been criticized for their shortcomings such as low strength,high brittleness,and high processing cost.In contrast,stainless steel BPs(SSBPs)have recently attracted much attention of domestic and foreign researchers because of their excellent comprehensive performance,low cost,and diverse options for automobile applications.However,the SSBPs are prone to corrosion and passivation in the PEMFC working environment,which lead to reduced output power or premature failure.This review is aimed to summarize the corrosion and passivation mechanisms,characterizations and evaluation,and the surface modification technologies in the current SSBPs research.The non-coating and coating technical routes of SSBPs are demonstrated,such as substrate component regulation,thermal nitriding,electroplating,ion plating,chemical vapor deposition,and physical vapor deposition,etc.Alternative coating materials for SSBPs are metal coatings,metal nitride coatings,conductive polymer coatings,and polymer/carbon coatings,etc.Both the surface modification technologies can solve the corrosion resistance problem of stainless steel without affecting the contact resistance,however still facing restraints such as long-time stability,feasibility of low-cost,and mass production process.This paper is believed to enrich the knowledge of high-performance and long-life BPs applied for PEMFC automobiles.

Analysis of the Influence of Geometrical Parameters on the Performance of a Proton Exchange Membrane Fuel Cell

A suitable channel structure can lead to efficient gas distribution and significantly improve the power density of fuel cells.In this study,the influence of two channel design parameters is investigated,namely,the ratio of the channel width to the bipolar plate ridge width(i.e.,the channel ridge ratio)and the channel depth.The impact of these parameters is evaluated with respect to the flow pattern,the gas composition distribution,the temperature field and the fuel cell output capability.The results show that a decrease in the channel ridge ratio and an increase in the channel depth can effectively make the distributions of velocity,temperature and concentration more uniform in each channel and improve the output capability of the fuel cell.An increase in the channel ridge ratio and depth obviously reduces the flow resistance and improves the flow characteristics.

Recent progress of antipoisoning catalytic materials for high temperature proton exchange membrane fuel cells doped with phosphoric acid

High-temperature proton exchange membrane fuel cells(HT-PEMFCs)have the unique advantages of fast electrode reaction kinetics,high CO tolerance,and simple water and thermal management at their operating temperature(120-300℃),which can effectively solve the hydrogen source problem and help achieve the dual-carbon goal.The catalysts in HT-PEMFCs are mainly Pt-based catalysts,which have good catalytic activity in the oxygen reduction reaction(ORR)and hydrogen oxidation reaction(HOR).However,in HT-PEMFCs,the high load of platinum-based catalysts to alleviate the limitation of strong adsorption of phosphoric acid(PA)on the platinum surface on activity expression leads to high cost,insufficient activity,decreased activity under long-term operation and carrier corrosion.The present review mainly summarizes the latest research progress of HT-PEMFCs catalysts,systematically analyzes the application of precious metal and non-precious metal catalysts in HT-PEMFCs,and unveils the structure-activity relationship and anti-PA poisoning mechanism.The current challenges and opportunities faced by HT-PEMFCs are discussed,as well as possible future solutions.It is believed that this review can provide some inspiration for the future development of high-performance HT-PEMFC catalysts.

Waste Water Treatment in Direct Borohydride Fuel Cell with Bipolar Membrane

It was established that application of bipolar membrane in a direct borohydride fuel cell (DBFC) with H2O2 co-generation enabled to keep constant pH in catholyte within 2.5 - 3.2 limits, which allowed us to carry out treatment of water polluted by organic compounds in fuel cell catholyte. Treatment of water was carried out by electro-Fenton and photo-electro-Fenton methods. With the view of efficiency, photo-electro-Fenton method of treatment was the most efficient, which enabled to decrease COD of catholytes containing (in each case) phenol, valsaren, 400 g/L dymethoate (BI-58) and valsaciper from 500 ppm to 30, 11, 9 and 3 ppm, respectively after 180 min treatment. By increasing the catholyte temperature from 20℃?to 40℃?in the same period, phenol COD fell to 5 ppm.

Effect of Terminal Design and Bipolar Plate Material on PEM Fuel Cell Performance

Bipolar plates perform as current conductors between cells, provide conduits for reactant gases, facilitate water and thermal management through the cells, and constitute the backbone of a fuel cell stack. Currently, commercial bipolar plates are made of graphite composite because of its relatively low interfacial contact resistance (ICR) and high corrosion resistance. However, graphite composite’s manufacturability, permeability, and durability of shock and vibration are unfavorable in comparison to metals. Therefore, metals have been considered as a replacement material for graphite composite bipolar plates. The main objective of this study is to evaluate the effect of terminal connection design and bipolar plate material on PEM fuel cell overall performance. The study has indicated that single cell performance can be improved by combining terminals into metallic bipolar plates. This terminal design reduces the internal cell resistance and eliminates the need for additional terminal plates. The improved single cell performance by 18% and the increased savings in hydrogen consumption by 15% at the current density of 0.30 A/cm2 was attributed to the robust metal to metal contact between the terminal and the metallic bipolar plates. However, connecting metal terminal directly into graphite bipolar plates did not exhibit similar improvement in the performance of graphite fuel cells because of their brittleness that could have caused damage in the plates and poor contacts.

Recent developments in electrocatalysts and future prospects for oxygen reduction reaction in polymer electrolyte membrane fuel cells

The main difficulty in the extensive commercial use of polymer electrolyte membrane fuel cells （PEMFCs） is the use of noble metals such as Pt-based electrocatalyst at the cathode, which is essential to ease the oxygen reduction reaction （ORR） in fuel cells （FCs）. To eliminate the high loading of Pt-based electrocatalysts to minimize the cost, extensive study has been carried out over the previous decades on the non-noble metal catalysts. Development in enhancing the ORR performance of FCs is mainly due to the doped carbon materials, Fe and Co-based electrocatalysts, these materials could be considered as probable substitutes for Pt-based catalysts. But the stability of these non-noble metal electrocatalysts is low and the durability of these metals remains unclear. The three basic reasons of instability are： （i） oxidative occurrence by H2O2, （ii） leakage of the metal site and （iii） protonation by probable anion adsorption of the active site. Whereas leakage of the metal site has been almost solved, more work is required to understand and avoid losses from oxidative attack and protonation. The ORR performance such as stability tests are usually run at low current densities and the lifetime is much shorter than desired need. Therefore, improvement in the ORR activity and stability afe the key issues of the non-noble metal electrocatalyst. Based on the consequences obtained in this area, numerous future research directions are projected and discussed in this paper. Hence, this review is focused on improvement of stability and durability of the non-noble metal electrocatalyst.

Design and Performance Analysis of Micro Proton Exchange Membrane Fuel Cells

This study describes a novel micro proton exchange membrane fuel cell(PEMFC)(active area,2.5 cm2).The flow field plate is manufactured by applying micro-electromechanical systems(MEMS) technology to silicon substrates to etch flow channels without a gold-coating.Therefore,this investigation used MEMS technology for fabrication of a flow field plate and presents a novel fabrication procedure.Various operating parameters,such as fuel temperature and fuel stoichiometric flow rate,are tested to optimize micro PEMFC performance.A single micro PEMFC using MEMS technology reveals the ideal performance of the proposed fuel cell.The optimal power density approaches 232.75 mW·cm-1 when the fuel cell is operated at ambient condition with humidified,heated fuel.

CFD Analysis of Spiral Flow Fields in Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells(PEMFCs)are largely used in various applications because of their pollution-free products and high energy conversion efficiency.In order to improve the related design,in the present work a new spiral flow field with a bypass is proposed.The reaction gas enters the flow field in the central path and diffuses in two directions through the flow channel and the bypass.The bypasses are arranged incrementally.The number of bypasses and the cross-section size of the bypasses are varied parametrically while a single-cell model of the PEMFC is used.The influence of the concentration of liquid water and oxygen in the cell on the performance of different flow fields is determined by means of Computational fluid dynamics(COMSOL Multiphysics software).Results show that when the bypass number is 48 and its cross-sectional area is 0.5 mm^(2),the cell exhibits the best performances.

Highly active ZIF-8@CNT composite catalysts as cathode materials for anion exchange membrane fuel cells

Developing non-precious metal-based inexpensive and highly active electrocatalysts for the oxygen reduction reaction(ORR)in alkaline media is important for fuel cell applications.Herein,we report a simple and effective synthesis of transition-metal-doped zeolitic imidazolate framework-8(ZIF-8)and carbon nanotube(CNT)composite catalysts(ZIF-8@CNT)prepared via high-temperature pyrolysis at 900℃.The catalysts were characterized using different physicochemical techniques and employed as cathode materials in anion exchange membrane fuel cells(AEMFC).The prepared metal-free(ZNT-900),single-metal-doped(Fe-ZNT-900,Co-ZNT-900)and binary-metal-doped(Fe_(1)Co_(1)-ZNT-900,Fe_(1)Co_(2)-ZNT-900)catalysts had a sufficient amount of N-doping with the presence of FeCo moieties in the carbon skeleton of the latter two materials.N_(2) adsorption–desorption isotherms showed that all the prepared catalysts possess a sufficient Brunauer–Emmett–Teller surface area with more micropores present in ZNT-900,while a combined micro–mesoporous structure was obtained for transition-metal-doped catalysts.Binary-metal-doped catalysts showed the highest number of ORR-active sites(pyridinic-N,pyrrolic-N,graphitic-N,M–Nx)and exhibited a half-wave potential(E_(1/2))of 0.846 and 0.847 V vs.RHE for Fe_(1)Co_(1)-ZNT-900 and Fe_(1)Co_(2)-ZNT-900,respectively,which surpassed that of the commercial Pt/C catalyst(E_(1/2)=0.834 V).In H_(2)–O_(2) AEMFCs,the Fe_(1)Co_(2)-ZNT-900 catalyst delivered a maximum power density(P_(max))of 0.171 W cm^(-2) and current density at 0.5 V(j_(0.5))of 0.326 A cm^(-2),which is very close to that of the Pt/C catalyst(P_(max)=0.215 W cm^(-2) and j_(0.5)=0.359 A cm^(-2)).The prepared ZIF-8@CNT catalysts showed remarkable electrocatalytic ORR activity in 0.1 M KOH solution and fuel cell performance comparable to that of the benchmark Pt/C catalyst.

Modelling Anti-Corrosion Coating Performance of Metallic Bipolar Plates for PEM Fuel Cells:A Machine Learning Approach

Proton exchange membrane(PEM)fuel cells have significant potential for clean power generation,yet challenges remain in enhancing their performance,durability,and cost-effectiveness,particularly concerning metallic bipolar plates,which are pivotal for lightweight compact fuel cell stacks.Protective coatings are commonly employed to combat metallic bipolar plate corrosion and enhance water management within stacks.Conventional methods for predicting coating performance in terms of corrosion resistance involve complex physical-electrochemical modelling and extensive experimentation,with significant time and cost.In this study machine learning techniques are employed to model metallic bipolar plate coating performance,diamond-like-carbon coatings of varying thicknesses deposited on SS316L are considered,and coating performance is evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy.The obtained experimental data is split into two datasets for machine learning modelling:one predicting corrosion current density and another predicting impedance parameters.Machine learning models,including extreme gradient boosting(XGB)and artificial neural networks(ANN),are developed,and optimized to predict coating performance attributes.Data preprocessing and hyperparameter tuning are carried out to enhance model accuracy.Results show that ANN outperforms XGB in predicting corrosion current density,achieving an R2>0.98,and accurately predicting impedance parameters with an R2>0.99,indicating that the models developed are very promising for accurate prediction of the corrosion performance of coated metallic bipolar plates for PEM fuel cells.

Effect of annealing on two different niobium-clad stainless steel PEMFC bipolar plate materials

Niobium (Nb)-clad stainless steels(SS) produced via roll bonding are being considered for use in the bipolar plates of polymer electrolyte membrane fuel cell(PEMFC) stacks. Because the roll bonding process induces substantial work hardening in the constituent materials, thermal annealing is used to restore ductility to the clad sheet so that it can be subsequently blanked, stamped and dimpled in forming the final plate component. Two roll bonded materials, niobium clad 340L stainless steel (Nb/340L SS) and niobium clad 434 stainless steel (Nb/434 SS) were annealed under optimized conditions prescribed by the cladding manufacturer. Comparative mechanical testing conducted on each material before and after annealing shows significant improvement in ductility in both cases. However, corresponding microstructural analyses indicate an obvious difference between the two heat treated materials. During annealing, an interlayer with thick less than 1 μm forms between the constituent layers in the Nb/340L SS, whereas no interlayer is found in the annealed Nb/434 SS material. Prior work suggests that internal defects potentially can be generated in such an interlayer during metal forming operations. Thus, Nb/434 SS may be the preferred candidate material for this application.

Conductive and corrosion behaviors of silver-doped carbon-coated stainless steel as PEMFC bipolar plates

Ni–Cr enrichment on stainless steel SS316 L resulting from chemical activation enabled the deposition of carbon by spraying a stable suspension of carbon nanoparticles; trace Ag was deposited in situ to prepare a thin continuous Ag-doped carbon film on a porous carbon-coated SS316 L substrate. The corrosion resistance of this film in 0.5 mol·L^（-1） H_2SO_4 solution containing 5 ppm F- at 80°C was investigated using polarization tests. The results showed that the surface treatment of the SS316 L strongly affected the adhesion of the carbon coating to the stainless steel. Compared to the bare SS316 L, the Ag-doped carbon-coated SS316 L bipolar plate was remarkably more stable in both the anode and cathode environments of proton exchange membrane fuel cell（PEMFC） and the interface contact resistance between the specimen and Toray 060 carbon paper was reduced from 333.0 m？·cm^2 to 21.6 m？·cm^2 at a compaction pressure of 1.2 MPa.

Influence of graphite particle size and its shape on performance of carbon composite bipolar plate

Bipolar plates for proton exchange membrane fuel cell (PEMFC) where polymer is used as binder and graphite is used as electric filler were prepared by means of compression molding technology. Study on the effects of graphite particle size and shape on the bipolar plate performance, such as electrical conductivity, strength, etc. showed that with decrease of graphite particle size, bulk electrical conductivity and thermometric conductivity decreased, but that flexural strength was enhanced. After spherical graphite occurrence in flake-like form, the flexural strength of the bipolar plate was enhanced, electrical conductivity increased but thermal conductivity decreased in direction paralleling pressure direction, and both electrical conductivity and thermometric conductivity reduced in direction perpendicular to pressure direction.

Graphene-based bipolar plates for polymer electrolyte membrane fuel cells

Bipolar plates(BPs)are a major component of polymer electrolyte membrane fuel cells(PEMFCs).BPs play a multifunctional character within a PEMFC stack.It is one of the most costly and critical part of the fuel cell,and hence the development of efficient and cost-effective BPs is of much interest for the fabrication of next-generation PEMFCs in future.Owing to high electrical conductivity and chemical inertness,graphene is an ideal candidate to be utilized in BPs.This paper reviews recent advances in the area of graphene-based BPs for PEMFC applications.Various aspects including the momentous functions of BPs in the PEMFC,favorable features of graphene.based BPs,performance evaluation of various reported BPs with their advantages and disadvantages,challenges at commercial level products and future prospects of frontier research in this direction are extensively documented.

Effect of electrode Pt-loading and cathode flow-field plate type on the degradation of PEMFC

The electrode Pt-loading has an effect on the number of active sites and the thickness of catalyst layer,which has huge influence on the mass transfer and water management during dynamic process in PEMFCs. In this study, membrane electrode assemblies with different Pt-loadings were prepared, and PEMFCs were assembled using those membrane electrode assemblies with traditional solid plate and water transport plate as cathode flow-field plates, respectively. The performance and electrochemical surface area of cells were characterized to evaluate the membrane electrode assemblies degradation after rapid currentvariation cycles. Scanning electron microscope and transmission electron microscope were used to investigate the decay of catalyst layers and Pt/C catalyst. With the increase of Pt-loading, the performance degradation of membrane electrode assemblies will be mitigated. But higher Pt-loading means thicker catalyst layer, which leads to a longer pathway of mass transfer, and it may result in carbon material corrosion in membrane electrode assemblies. The decay of Pt/C catalyst in cathode is mainly caused by the corrosion of carbon support, and the degradation of anode Pt/C catalyst is a consequence of migration and aggregation of Pt particles. And using water transport plate is beneficial to alleviating the age of cathode Pt/C catalyst.

Fe,N,S-doped porous carbon as oxygen reduction reaction catalyst in acidic medium with high activity and durability synthesized using CaCl_2 as template

Proton exchange membrane fuel cells suffer from the sluggish kinetics of the oxygen reduction reaction(ORR)and the high cost of Pt catalysts.In the present work,a high‐performance ORR catalystbased on Fe,N,S‐doped porous carbon(FeNS‐PC)was synthesized using melamine formaldehyderesin as C and N precursors,Fe(SCN)3as Fe and S precursors,and CaCl2as a template via a two‐stepheat treatment without a harsh template removal step.The results show that the catalyst treated at900℃(FeNS‐PC‐900)had a high surface area of775m2/g,a high mass activity of10.2A/g in anacidic medium,and excellent durability;the half‐wave potential decreased by only20mV after10000potential cycles.The FeNS‐PC‐900catalyst was used as the cathode in a proton exchangemembrane fuel cell and delivered a peak power density of0.49W/cm2.FeNS‐PC‐900therefore hasgood potential for use in practical applications.

Performance of Nb_(0.8)Zr_(0.2) Layer-Modified AISI430 Stainless Steel as Bipolar Plates for Direct Formic Acid Fuel Cells

To improve the interfacial conductivity and corrosion resistance of AISI430 stainless steel(430 SS)as bipolar plates for direct formic acid fuel cells(DFAFCs),a Nb_(0.8)Zr_(0.2) layer has been successfully synthesized via the pulsed laser deposition(PLD)technique on the surface of 430 SS.This Nb_(0.8)Zr_(0.2) layer is smooth,uniform,and comparatively compact without any surface flaw and micropore.Investigation under the simulated anodic environment of DFAFCs(0.05 M H_(2)SO_(4)+2 ppm HF+10 M HCOOH at 70℃)shows that the corrosion resistance of 430 SS is obviously ameliorated after the PLD modification.In addition,the interfacial contact resistance of Nb_(0.8)Zr_(0.2)-430 SS(6.0 mΩcm^(2))is much smaller than that of bare 430 SS(151.3 mΩcm^(2))at the clamping force of 140 N cm^(-2).Besides,diff erent from the highly increased interfacial contact resistance of bare 430 SS,the Nb_(0.8)Zr_(0.2)-430 SS shows a minor increase resistance after potentiostatic tests in simulated anodic environment of DFAFCs.