Performance Of Proton Exchange Membrane Fuel Cell Research Articles

Influence of PTFE content on structural parameters of microporous layer and its performance in PEMFCs

The gas diffusion layer (GDL) is the water management center of proton exchange membrane fuel cells (PEMFCs), and the composition and structural parameters of this microporous layer (MPL) seriously affect the performance of fuel cells. Herein, a three-dimensional model of MPL structure, with different PTFE contents, is established based on the close-packed structure model, and the concept of critical pigment volume concentration(CPVC) during the coating process is introduced to elucidate what. The porosity of MPL with different PTFE contents is calculated by using the di-n-butyl phthalate (DBP) absorption number of Vulcan XC-72 and compared with the experimental values. The influence of PTFE content and structural parameters on the performance of a single cell is analyzed based on the porosity, surface morphology, water and gas permeabilities, hydrophilicity, hydrophobicity and surface resistivity of MPLs with different PTFE contents. The optimal PTFE content in MPL is determined to be 20–30%, and the maximum power density of a single cell is achieved to be 1.55 W/cm2.

Nanostructure Engineering of Cathode Layers in Proton Exchange Membrane Fuel Cells: From Catalysts to Membrane Electrode Assembly.

The membrane electrode assembly (MEA) is the core component of proton exchange membrane fuel cells (PEMFCs), which is the place where the reaction occurrence, the multiphase material transfer and the energy conversion, and the development of MEA with high activity and long stability are crucial for the practical application of PEMFCs. Currently, efforts are devoted to developing the regulation of MEA nanostructure engineering, which is believed to have advantages in improving catalyst utilization, maximizing three-phase boundaries, enhancing mass transport, and improving operational stability. This work reviews recent research progress on platinum group metal (PGM) and PGM-free catalysts with multidimensional nanostructures, catalyst layers (CLs), and nano-MEAs for PEMFCs, emphasizing the importance of structure-function relationships, aiming to guide the further development of the performance for PEMFCs. Then the design strategy of the MEA interface is summarized systematically. In addition, the application of in situ and operational characterization techniques to adequately identify current density distributions, hot spots, and water management visualization of MEAs is also discussed. Finally, the limitations of nanostructured MEA research are discussed and future promising research directions are proposed. This paper aims to provide valuable insights into the fundamental science and technical engineering of efficient MEA interfaces for PEMFCs.

Effect of Solvent Ratio (Ethylene Glycol/Water) in the Synthesis of Pt/C Cathode Catalysts on PEM Fuel Cell Performance

Abstract The ethylene glycol (EG)/water mixture composition of an alkaline one-step polyol synthesis for Pt/C catalysts was systematically investigated and optimized for a low ethylene glycol content with regards to resulting Pt particle size and electrochemical performance of membrane electrode assemblies tested as proton exchange membrane (PEM) fuel cell cathode catalysts. Beginning test fuel cell data show a possible reduction of the required EG amount per gram of synthesized catalyst by up to 98% without significantly compromising the initial electrochemical performance. Taking catalyst durability into account, a Pt/C catalyst synthesized with 40 vol% H2O and 32 mM Pt precursor concentration showed a decent initial electrochemical performance (716 mV at 1 A cm-2) as well as an accelerated stress test-derived stability similar to an internal reference catalyst, obtained with 100 vol% EG. In summary, our study shows that optimizing the amount of water and platinum precursor in the synthesis process can lead to catalysts with excellent performance for PEM fuel cells while contributing significantly to cost reduction by using less EG during synthesis.

Self‐Sacrificial Template Synthesis of Fe‐N‐C Catalysts with Dense Active Sites Deposited on A Porous Carbon Network for High Performance in PEMFC

AbstractIron‐nitrogen‐carbon (Fe‐N‐C) single‐atom catalysts are promising sustainable alternatives to the costly and scarce platinum (Pt) to catalyze the oxygen reduction reactions (ORR) at the cathode of proton exchange membrane fuel cells (PEMFCs). However, Fe‐N‐C cathodes for PEMFC are made thicker than Pt/C ones, in order to compensate for the lower intrinsic ORR activity and site density of Fe‐N‐C materials. The thick electrodes are bound with mass transport issues that limit their performance at high current densities, especially in H2/air PEMFCs. Practical Fe‐N‐C electrodes must combine high intrinsic ORR activity, high site density, and fast mass transport. Herein, it has achieved an improved combination of these properties with a Fe‐N‐C catalyst prepared via a two‐step synthesis approach, constructing first a porous zinc‐nitrogen‐carbon (Zn‐N‐C) substrate, followed by transmetallating Zn by Fe via chemical vapor deposition. A cathode comprising this Fe‐N‐C catalyst has exhibited a maximum power density of 0.53 W cm−2 in H2/air PEMFC at 80 °C. The improved power density is associated with the hierarchical porosity of the Zn‐N‐C substrate of this work, which is achieved by epitaxial growth of ZIF‐8 onto g‐C3N4, leading to a micro‐mesoporous substrate.

Regulation Strategies for Fe-N-C and Co-N-C Catalysts for the Oxygen Reduction Reaction.

Proton exchange membrane fuel cells (PEMFCs) and alkaline membrane fuel cells (AEMFCs) have received great attention as energy devices of the next generation. Accelerating oxygen reduction reaction (ORR) kinetics is the key to improve PEMFC and AEMFC performance. Platinum-based catalysts are the most widely used catalysts for the ORR, but their high price and low abundance limit the commercialization of fuel cells. Non-noble metal-nitrogen-carbon (M-N-C) is considered to be the most likely material class to replace Pt-based catalysts, among which Fe-N-C and Co-N-C have been widely studied due to their excellent intrinsic ORR performance and have made great progress in the past decades. With the improvement of synthesis technology and a deeper understanding of the ORR mechanism, some reported Fe-N-C and Co-N-C catalysts have shown excellent ORR activity close to that of commercial Pt/C catalysts. Inspired by the progress, regulation strategies for Fe-N-C and Co-N-C catalysts are summarized in this Review from 5 perspectives: (1) coordinated atoms, (2) environmental heteroatoms and defects, (3) dual-metal active sites, (4) metal-based particle promoters, and (5) curved carbon layers. We also make suggestions on some challenges facing Fe-N-C and Co-N-C research.

Numerical and Experimental Investigation of Performance and Flooding Phenomena of a PEM Fuel Cell with and without Micro-Porous Layers

This work presents the results of manufacturing a single Proton Exchange Membrane Fuel Cell (PEMFC) with Micro-Porous Layers (MPLs) and an active area of 25 cm2, and the experimental study required to build its polarization curve. Based on the physical model data, a numerical model of this PEMFC is created in the ANSYS PEM Fuel Cell module. Numerical simulations were performed with boundary conditions consistent with the experimental conditions on the test station. The calculation and experimental result comparison of the polarization curves for voltages ranging from 0.29 V to 0.94 V proved that the utilized numerical model is highly reliable. The simulation of PEMFC without MPLs was conducted according to other stable input parameters and boundary conditions. The results show that the PEMFC performance decreases significantly due to the flooding phenomenon inside PEMFC without MPLs compared to PEMFC with MPLs. Such phenomena are challenging to observe experimentally. Numerical modeling can be further used to optimize the fuel cell components.

Electrospun catalyst layers using short-side-chain ionomer for low platinum and high performance PEMFCs

Proton exchange membrane fuel cells (PEMFCs) should further reduce the platinum consumption to lower their manufacturing costs and life-cycle carbon emissions. However, the performance of the catalyst layers with low-Pt loading needs to be improved. Short-side-chain (SSC) ionomers have been proven to enhance the catalytic activity of conventional catalyst layers. In this work, the SSC ionomer was applied to the electrospun catalyst layer, and achieved a remarkable improvement in the performance. With the use of commercially available catalyst, the membrane electrode assemblies (MEAs) prepared in this work exhibited a low total-Pt-consumption of 0.064 g kW−1 (stoichiometric ratios of 1.5/2.5 for H2/air, 80°C, 100 kPa) and achieved the 2025 target proposed by the US Department of Energy. Separating activation, ohmic, and concentration overpotentials, the performance enhancement of the electrospun catalyst layer mainly came from the decrease of ohmic overpotential and concentration overpotential. The electrospun ionomer membrane without catalyst was used as a research model to explore the proton transport properties inside the electrospun catalyst layer. The results showed that in the range of PEMFC operating temperature, the proton conductivity of the electrospun catalyst layer could be higher, but meanwhile the proton-conduction activation energy was also elevated. Compared with the conventional catalyst layer, the electrospun catalyst layer showed obviously better performance before and after accelerated stress test, thus verifying the practicality of the electrospun catalyst layers. This work provided a reference for the development of low platinum and high performance catalyst layers.

Numerical simulation for non-uniform PtCo catalyst degradation under different coolant conditions and its effect on PEMFC performance

Long-term non-uniform temperature, pressure and reaction rates distributions in the proton exchange membrane fuel cells (PEMFCs) may result in local catalyst degradation and deteriorate PEMFC performance. However, the problem of non-uniform catalyst degradation in PEMFC stacks is still incompletely understood due to the lacking of advanced experimental methods and three-dimensional (3D) catalyst aging models. In this study, a 3D PtCo alloy catalyst degradation model under voltage cycles is built and a 25 cm2 PEMFC stack containing realistic cathode, anode as well as coolant flow fields is used as the computational domain to analyze in detail the influence of non-uniform catalyst degradation on the performance of the PEMFC during different coolant conditions. The simulation results show that the non-uniform catalyst degradation is strongly dependent on the cathode flow field structure. It can alleviate non-uniform catalyst degradation as well as contribute to improving PEMFC performance when the coolant flow direction is the same as the air, and both coolant flow rate and inlet temperature also are found to significantly affect the local catalyst degradation behavior. Therefore, an optimally designed cathode flow fields structure as well as good water and heat management during operation can help to extend the service life of the PEMFC.

Numerical and experimental study on designs and performances of multi-serpentine flow field with bend-area block for proton exchange membrane fuel cell

The geometric modification of the flow field is an effective measure to improve the performance of proton exchange membrane fuel cell (PEMFC) and the mass transfer ability of reactants. In this paper, serpentine channels with geometric parameters containing various blocks to generate gas forced convection at the U-bends are established and numerically studied. Setting blocks at different angles at U-bends has different effects at the corners, offering a more flexible and variable region of active gas diffusion in the vertical direction. The area of high vertical velocity is increased by the Angle-Height combination design with low pressure drop and uniform temperature distribution. It is demonstrated that a vertical velocity of 0.4 m s−1 can be achieved around the block in the 135° series with half-height corner blocks, proving the existence of the mass transfer enhancement. Subsequently, experimental testing is conducted to verify the feasibility of the optimized flow field. The experimental results support the trend of block height influencing cell performance, with a maximum power density increase of 3.4 %. Modifying the U-bend corner structure has proven to be an effective technique for improving the overall performance of PEMFC, which can serve an important guidance for future flow field design.

Evaluating electrocatalytic activities of Pt, Pd, Au and Ag-based catalyst on PEMFC performance: A review

This comprehensive review article highlights recent advancements of Pt and Pd-based electrocatalysts, covering Pt and Pd alloys, Pt-M and Pd-M core-shell structures, nanosize/nanostructure effects, addition of support material, doping effects, and post-treatment for the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) in Proton exchange membrane fuel cell (PEMFC). Additionally, it delves into other precious metals such as Gold (Au) and Silver (Ag) for ORR and HOR in PEMFC. The role and contribution of incorporating other elements or materials such as metal oxides, metal carbides, transition metal oxides, carbon support, and non-carbon support are thoroughly discussed. The most promising methods are also described, with a special emphasis on narrow particle size, nanostructure, and low loading of novel Pt- and Pd-based catalysts. Furthermore, the advantages and shortcomings of these catalysts for electrocatalysis are analyzed, along with the influence of the nanostructure and morphology of the electrocatalyst materials on electrochemical performance.

Evaluation criterion of cathode flow field in air-cooling proton exchange membrane fuel cells

In recent years, air-cooling proton exchange membrane fuel cells (PEMFCs) have become a priority choice for applications due to their lightweight and simple structure. In this work, the mechanism of cathode flow field characteristics on PEMFC performance is revealed, and the evaluation criterion of the cathode flow field is proposed. A 2 kW PEMFC stack of 100 cells is used, and the different uniformity and airflow rate of the cathode flow field are achieved by varying the position and number of cathode fans with a constant total parasitic fan power. The PEMFC power, cathode temperature distribution, and single-cell voltage consistency of different configurations are evaluated. The results show that the maximum difference in output power and maximum temperature of different PEMFC cathode flow field configurations reach 6.5% and 22.3%, respectively. Three key parameters are proposed to evaluate the PEMFC cathode flow field: total uniformity rate can evaluate the overall uniformity of the PEMFC cathode flow field, vertical uniformity rate can be used to predict and evaluate the single-cell voltage consistency of the PEMFC stack, and cathode airflow rate determines the continuous operating power of the PEMFC stack. The evaluation criterion can guide the design and optimization of air-cooling PEMFCs.

Application of template method in fabricating ordered gas diffusion layer of PEMFC

ABSTRACT As a core component of proton exchange membrane fuel cell (PEMFC), gas diffusion layer (GDL) takes an important role in the migration of gas, liquid, heat, and electrons. Optimizing GDL microstructure is crucial to improve the gas-liquid flowing behavior and enhance PEMFC performance. Therefore, an ordered GDL is designed by coupling the template method and stacking multiple fiber layers method to provide the large holes for water elimination and the small pores for gas delivery. The ordered GDL possesses excellent mass transfer capacity, which can improve the PEMFC performance compared with commercial GDL under high relative humidity (RH). At RH 100% and 70°C, the PEMFC with ordered GDL achieves the maximum peak power density of 0.92 W cm−2, which realizes an increment of 10.8% compared with commercial GDL. However, with a decrease in RH, the ohmic loss gradually occupies the primary contribution to the performance compared with the mass transfer capacity, resulting in a downward trend of the performance of PEMFC with ordered GDL. This work provides a simple and efficient strategy to design the ordered pore structure of GDL, and the outcomes have the potential of being implemented in the future PEMFC vehicles.

Bio-inspired sinusoidally-waved flow fields with exchange channels to enhance PEMFC performance

Wave-shaped structures inspired by cuttlefish fins have been applied to the design of flow fields for proton exchange membrane fuel cells (PEMFCs). However, the wave structures often cause high parasitic power. Herein, we intend to address this issue by introducing exchange channels (ECs) between neighboring wave channels. First, the performances of bio-inspired sinusoidally-waved flow fields (BSWFFs) of different sinusoidal parameters are compared to identify the optimal sinusoidal structure. Subsequently, ECs are introduced into BSWFFs with the optimal sinusoidal structure to obtain EC-BSWFFs, and EC-BSWFFs with different numbers of ECs are compared. The introduction of ECs improves the distribution of reactant gases, pressure distribution, water management and reduces parasitic power density. Specifically, the maximum net power density of the single-cell PEMFC with EC-12 is enhanced by 10.26% compared to that of the conventional parallel flow field. Moreover, as the number of ECs in EC-BSWFFs increases, the uniformity of pressure distribution gradually increases and the pressure drop becomes smaller, suggesting a balance between performance and durability. Therefore, this work affords valuable insights to solve the difficulties of excessive pressure drop and inhomogeneous reactant distribution for waved flow fields.

Intelligent control based on single-input interval type-2 fuzzy iPI and super twisting nonlinear sliding mode compensator for regulating PEMFC output voltage

The control of Proton Exchange Membrane Fuel Cell (PEMFC) is exceptionally challenging due to its complex nonlinearity, slow dynamics and load disturbance. In this paper, an Adaptive Model Free Control (AMFC) approach is introduced for regulating the PEMFC output voltage under load perturbation and measurement noise conditions. The proposed method consists of four sub-elements. Firstly, an Extended State Observer (ESO) based on a Single-Input Interval Type-2 Fuzzy intelligent PI (SI-IT-2-FLC-iPI) scheme is designed to enhance the performance of PEMFC. Secondly, a Nonlinear Sliding Mode Control-based Super Twisting Algorithm (NSMC-STA) is used as an auxiliary control approach to reduce the estimation error and ameliorate the system robustness. Thirdly, a Forgotten Recursive Least Square Error (FRLSE) is applied for adjusting the physical parameter of MFC and further ameliorating the control response. Finally, all these elements are merged together within what it is called Ultra Local Model (ULM).Through extensive simulation, the efficacy of the proposed regulator in accurately tracking the output signal is showcased, outperforming conventional controllers with remarkable improvements. The system achieves 0.001 steady-state error, 0% overshoot and settling time of approximately 8.9 s, which is good enough in the context of standalone fuel cell applications.

Optimization strategies and diagnostic techniques for water management in proton exchange membrane fuel cells

Proton exchange membrane fuel cells (PEMFCs) are efficient and zero emission energy conversion technology with promising application prospects towards carbon neutrality. The PEMFC's performance is largely affected by the poor water management, which is a substantial concern for long term durability. Herein, we overview the water management problems in PEMFCs, such as flooding and dehydration of membrane electrode assembly and analyze the causes and their impacts on the device performance. Major problems such as flooding impedes the gas transport and electrode reactions, while dehydration increases the membrane resistance and hinders proton transport. We have thoroughly overviewed several electrochemical and physicochemical diagnostic techniques for water management in PEMFCs. Additionally, material development and optimization approaches for the flow field structural design are explored in order to improve mass transport and wetting characteristics for optimized water management. Therefore, it is anticipated that this review will provide insights into the effective operation of PEMFCs as well as practical guidance for resolving water management issues in PEMFCs and associated technologies, like PEM water and CO2 electrolyzers.

A one-dimensional numerical model of carbon corrosion in catalyst layers of proton exchange membrane fuel cells

Understanding interaction between carbon corrosion and physicochemical processes inside proton exchange membrane fuel cells (PEMFCs) is important. A one-dimensional carbon corrosion model considering cathode catalyst layer (CCL) structure evolutions is established and coupled with one-dimensional PEMFC performance model. The coupled model is validated and employed to predict CCL structure evolution and PEMFC performance degradation during accelerated stress test. The results find that high relative humidity can enhance performance but accelerate carbon corrosion. Increasing carbon loading and decreasing ionomer weight can improve both performance and durability. Low Pt loading leads to reduced performance and durability. There exists an optimal carbon diameter leading to the best performance. Small carbon diameter can enhance cell durability. Proper gradient CCL design can enhance durability at cost of small initial performance reduction. Finally, an optimized structure is proposed with 21.7 % higher current density at 0.6 V and 5.2 % lower performance loss compared with base case.

A Review of Proton Exchange Membrane Degradation Pathways, Mechanisms, and Mitigation Strategies in a Fuel Cell

Proton exchange membrane fuel cells (PEMFCs) have the potential to tackle major challenges associated with fossil fuel-sourced energy consumption. Nafion, a perfluorosulfonic acid (PFSA) membrane that has high proton conductivity and good chemical stability, is a standard proton exchange membrane (PEM) used in PEMFCs. However, PEM degradation is one of the significant issues in the long-term operation of PEMFCs. Membrane degradation can lead to a decrease in the performance and the lifespan of PEMFCs. The membrane can degrade through chemical, mechanical, and thermal pathways. This paper reviews the different causes of all three routes of PFSA degradation, underlying mechanisms, their effects, and mitigation strategies. A better understanding of different degradation pathways and mechanisms is valuable in producing robust fuel cell membranes. Hence, the progress in membrane fabrication for PEMFC application is also explored and summarized.

Fe-N-C core–shell catalysts with single low-spin Fe(II)-N4 species for oxygen reduction reaction and high-performance proton exchange membrane fuel cells

Fe-N-doped carbon materials (Fe-N-C) are promising candidates for oxygen reduction reaction (ORR) relative to Pt-based catalysts in proton exchange membrane fuel cells (PEMFCs). However, the intrinsic contributions of Fe-N4 moiety with different chemical/spin states (e.g. D1, D2, D3) to ORR are unclear since various states coexist inevitably. In the present work, Fe-N-C core–shell nanocatalyst with single low-spin Fe(II)-N4 species (D1) is synthesized and identified with ex-situ ultralow temperature Mössbauer spectroscopy (T = 1.6 K) that could essentially differentiate various Fe-N4 states and invisible Fe-O species. By quantifying with CO-pulse chemisorption, site density and turnover frequency of Fe-N-C catalysts reach 2.4 × 1019 site g−1 and 23 e site−1 s−1 during the ORR, respectively. Half-wave potential (0.915 VRHE) of the Fe-N-C catalyst is more positive (approximately 54 mV) than that of Pt/C. Moreover, we observe that the performance of PEMFCs on Fe-N-C almost achieves the 2025 target of the US Department of Energy by demonstrating a current density of 1.037 A cm−2 combined with the peak power density of 0.685 W cm−2, suggesting the critical role of Fe(II)-N4 site (D1). After 500 h of running, PEMFCs still deliver a power density of 1.26 W cm−2 at 1.0 bar H2-O2. An unexpected rate-determining step is figured out by isotopic labelling experiment and theoretical calculation. This work not only offers valuable insights regarding the intrinsic contribution of Fe-N4 with a single spin state to alkaline/acidic ORR, but also provides great opportunities for developing high-performance stable PEMFCs.

The Lifetime of Hydroxyl Radical in Realistic Fuel Cell Catalyst Layer.

The lifetime of hydroxyl radicals (⋅OH) in the fuel cell catalyst layer remains uncertain, which hampers the comprehension of radical-induced degradation mechanisms and the development of longevity strategies for proton-exchange membrane fuel cells (PEMFCs). In this study, we have precisely determined that the lifetime of ⋅OH radicals can extend up to several seconds in realistic fuel cell catalyst layers. This finding reveals that ⋅OH radicals are capable of carrying out long-range attacks spanning at least a few centimeters during PEMFCs operation. Such insights hold great potential for enhancing our understanding of radical-mediated fuel cell degradation processes and promoting the development of durable fuel cell devices.

The impact of baffle and taper channel tilt angle on the output performance of proton‐exchange membrane fuel cells

AbstractThe performance and durability of proton‐exchange membrane fuel cells (PEMFCs) are constrained by fuel delivery and water management. Based on parallel and serpentine flow fields, the effects of triangular baffles (30°, 45°, and 60°) and conical runners (1°, 2°, and 3°) on the performance output of PEMFC at different angles are studied. The three‐dimensional and multi‐phase models are established by using the simulation software package (ANSYS FLUENT). The findings demonstrate that the battery's output performance reaches its peak when the baffle angle is set at 45°. When the output current density is 0.7 A/cm2, the power density of the 45° baffle increases by 18.87%. The pressure loss is not only lower than that of the 60° baffle but also exhibits no significant difference when compared to the 30° baffle. In addition, the introduction of conical channels has enhanced the output performance of PEMFCs in comparison to the traditional serpentine flow field. The power density of the 2°tapered channel exhibits a 12.65% increase when the output current density reaches 0.8 A/cm2. However, the performance output of the 3°tapered channel is inferior to that of the conventional serpentine flow field.