PEMFC Performance Research Articles

ONIOM Study on the Influence of Aluminium in Propylsulfonic Acid‐functionalized ZSM‐5 for Proton Transfer

AbstractProton exchange membrane fuel cells (PEMFCs) are promising candidates for clean and efficient power sources. Zeolite nanoparticle membranes have been introduced as potential new membrane materials to improve the performance of PEMFCs. Understanding the proton transport mechanism on zeolite nanoparticle membranes at the atomic level is crucial in developing more efficient PEMFCs. We investigated the influence of aluminium to initiate proton transfer within zeolite fragments by performing geometry conformation of hydrated propylsulfonic acid‐functionalized zeolite ZSM‐5 clusters from one to six water molecules using four different ONIOM schemes; ONIOM(B3LYP:HF) and ONIOM(B3LYP:PM3) in gas phase and within polarizable continuum model (PCM) of water system. Results show that four water molecules are required for second proton dissociation to occur in Al systems, whereas at least five water molecules are needed in their counterpart systems. Analysis of the results suggests that the presence of Al atom in the zeolite backbone increases the electronegativity of the oxygen atom of the sulfonic acid. The oxygen provides an active site for the acidic proton to participate and increased the ability of hydrogen to dissociate itself and form hydronium cations. Our ONIOM calculation proves that ONIOM(B3LYP:PM3) method of calculation provides a reliable result with minimal computational cost.

Synergistic Utilization of a CeO2-Anchored Bifunctionalized Metal–Organic Framework in a Polymer Nanocomposite toward Achieving High Power Density and Durability of PEMFC

The free radicals produced during the long-term operation of fuel cells can accelerate the chemical degradation of the proton exchange membrane (PEM). In the present work, the widely used free radical scavenger CeO2 was anchored on amino-functionalized metal–organic frameworks, and flexible alkyl sulfonic acid side chains were tethered onto the surface of inorganic nanoparticles. The prepared CeO2-anchored bifunctionalized metal–organic framework (CeO2-MNCS) was used as a promising synergistic filler to modify the Nafion matrix for addressing the detrimental effect of pristine CeO2 on the performance and durability of PEMs, including decreased proton conductivity and the migration problem of CeO2. The obtained hybrid membranes exhibited a high proton conductivity up to 0.239 S cm–1, enabling them to achieve a high power density of 591.47 mW cm–2 in a H2/air PEMFC single cell, almost 1.59 times higher than that of recast Nafion. After 115 h of acceleration testing, the OCV decay ratio of the hybrid membrane was decreased to 0.54 mV h–1, which was significantly lower than that of recast Nafion (2.18 mV h–1). The hybrid membrane still maintained high power density, low hydrogen crossover, and unabated catalytic activity of the catalyst layer after the durability test. This study provides an effective one-stone-two-birds strategy to develop highly durable PEMs by immobilizing CeO2 without sacrificing proton conductivity, allowing for the realization of improvement on the performance and sustained durability of PEMFC simultaneously.

Proton Exchange Membrane Fuel Cell as an Alternative to the Internal Combustion Engine for Emission Reduction: A Review on the Effect of Gas Flow Channel Structures

Proton exchange membrane fuel cells are a new energy technology with great potential due to advantages such as high efficiency and no pollution. The structure of the gas flow channels has a profound impact on the overall performance of the fuel cell. Different flow channel geometries have their own advantages and disadvantages, and a good understanding of the influence of these structures on performance can provide a reference for the design and improvement of flow channel geometries in various application contexts. Numerical models can be used as a reasonable and reliable tool to evaluate the influence of operating and structural parameters on cell performance and service time by simulating the transport processes of substances and heat as well as electrochemical reactions inside the fuel cell and can be used for the optimisation of cell design. This paper reviews the recent models of proton exchange membrane fuel cells, summarises and analyses the effect of gas flow channels on fuel cells, and organises and concludes efficient design of flow channel structures to enhance PEMFC performance in terms of the cross-section shape, length, width, number of flow channels, and baffle position.

Influence of Operating and Electrochemical Parameters on PEMFC Performance: A Simulation Study

Proton exchange membrane fuel cell, or polymer electrolyte fuel cell, (PEMFC) has received a significant amount of attention for green energy applications due to its low carbon emission and less other toxic pollution capacity. Herein, we develop a three-dimensional (3D) computational fluid dynamic model. The values of temperature, pressure, relative humidity, exchange coefficient, reference current density (RCD), and porosity values of the gas diffusion layer (GDL) were taken from the published literature. The results demonstrate that the performance of the cell is improved by modifying temperature and operating pressure. Current density is shown to degrade with the rising temperature as explored in this study. The findings show that at 353 K, the current density decreases by 28% compared to that at 323 K. In contrast, studies have shown that totally humidified gas passing through the gas channel results in a 10% higher current density yield, and that an evaluation of a 19% higher RCD value results in a similar current density yield.

Three-Dimensional Simulation on the Effects of Different Parameters and Pt Loading on the Long-Term Performance of Proton Exchange Membrane Fuel Cells

The choice of platinum loading and the choice of the operating parameters of the cell are crucial in order to enhance a PEMFC’s endurance and, at the same time, to raise its performance. In this paper, a single-channel PEMFC counter-current model is developed to investigate the effects of a 0.3 mg/cm² Pt loading model and a 0.1 mg/cm² Pt loading model on the performance and durability of PEMFCs with different operating pressures, different cathode stoichiometry, and different channel and plate widths. It was found that increasing the PEMFC operating pressure and cathode stoichiometry would increase the cell performance and have some improvement for durability. Additionally, increasing the channel/plate width ratio would improve the cell performance while decreasing the cell durability.

Effect of cooling surface temperature difference on the performance of high-temperature PEMFCs

Internal temperature distribution of the high-temperature proton exchange membrane fuel cell (HT-PEMFC) is affected by the cooling temperature, heat generation and reactant gas flow. Reasonable temperature control is helpful to improve the fuel cell performance and durability. In this work, a three-dimensional model that couples the reactant flows, species transport, heat transfer, charge transfer, and electrochemical reaction, was developed to simulate the HT-PEMFC operation. A solid mechanics model was established to analyze the stress distribution of the fuel cell. The polarization curves, distributions of temperature, membrane proton conductivity, current density and stress are investigated for different cooling surface temperature. Furthermore, the effect of assembly temperature on the stress of phosphoric acid-doped polybenzimidazole (PBI) membrane is discussed. Results reveals that the peak power density and uniformity of current density decrease with the increase of cooling surface temperature difference. The peak power density decreases by 9.14% when the temperature difference increases from 0 K to 40 K. The cooling surface temperature difference of less than 10 K and the voltage range in 0.5–0.7 V can achieve better current density uniformity and smaller current density change rate. In addition, the membrane in fuel cell has the highest stress, and increasing the assembly temperature is helpful to reduce the membrane stress. When the assembly temperature increases from 293.15 K to 343.15 K, the max and min compressive stresses in membrane in-plane decrease from 39.436 MPa to 31.416 MPa–24.934 MPa and 17.369 MPa at the temperature difference of 30 K, which decreases by 36.77% and 44.7%, respectively.

Influence of Different Ship Harmonic Vibration Directions on Dynamic Response of PEMFC

For the sake of study the applicability of PEMFC on ships, a three-dimensional single channel fuel cell model was established. The vibration load was loaded on the model through dynamic grid technology and user-defined function (UDF) method. The output voltage and reactive gas distribution of PEMFC loaded in different vibration directions were compared and analyzed. The results show that ship vibration will affect the transmission of components in the battery, resulting in incomplete electrochemical reaction and degradation of PEMFC performance. The influence of vertical vibration is greater than that of longitudinal vibration and lateral vibration.

Evaluation of flow field design effects on proton exchange membrane fuel cell performance

Fluid distribution, conduction, and heat control are important phenomenon in the fuel cell fraternity, therefore it is crucial to develop a state-of-the-art bipolar plate (BP) to attain optimum cell performance. Metal foam (MF) and fine mesh have attracted a lot of attention in mitigating some of the challenges associated with straight, and serpentine channels. In this study, MF, 3D fine mesh, fine wire mesh (FWM) flow fields are compared with triple serpentine flow field to develop an optimum design for improved PEMFC performance. Two different foam designs are studied to attenuate the existing drawback associated with MF, mainly caused by high water retention. The 3D fine mesh is leading in performance under anodic and cathodic stoichiometry of 1 and 3 respectively. On increasing the anodic and cathodic stoichiometry to 1.2 and 3.5 respectively, the FWM took the lead. This is brought by the improved water drainage under high stoichiometry. Because FWM is already in mass production, although for other purposes, it is cost competitive over the other designs. The fine mesh and the MF have the potential to break down large water droplet making them easy to drain. They also showed symmetric fluid flow, compared to the serpentine design.

Influence of Crack Formation at the Catalyst Layer and Membrane Interface on the Performance of Pemfc

Influence of Crack Formation at the Catalyst Layer and Membrane Interface on the Performance of Pemfc

A Numerical Parametric Study on the Impacts of Mass Fractions of Gas Species on PEMFC Performance

A Numerical Parametric Study on the Impacts of Mass Fractions of Gas Species on PEMFC Performance

Scalable production of an intermetallic Pt–Co electrocatalyst for high-power proton-exchange-membrane fuel cells

High-power PEMFC performance requires holistic consideration of activation, ohmic, and concentration losses. A scalable production method of ORR electrocatalysts is developed to tackle all the critical factors to achieve practical PEMFC operation.

냉각 채널을 통한 PEMFC 성능 향상 수치해석

고분자 전해질막 연료전지(PEMFC)는 수소와 산소의 전기화학적 반응으로 화학 에너지를 전기에너지로 변환하는 장치다. 전기화학 반응에 의해 발생하는 열과 물은 PEMFC의 성능을 저하시킬 수 있으므로 PEMFC의 성능 및 수명을 향상시키기 위해 냉각 채널 설계는 중요하다. 본 연구에서는 냉각 채널이 존재하지 않는 구조와 냉각 채널이 존재하는 구조의 PEMFC를 시뮬레이션하고 수치적으로 비교하여 냉각 채널이 PEMFC에 미치는 영향을 분석한다. 전압이 일정할 때 냉각 채널이 존재하는 PEMFC는 산소 확산과 전기화학적 반응 속도가 증가하여 더 높은 전류 밀도와 전력 밀도를 보인다. 냉각 채널이 존재하는 PEMFC의 성능은 냉각 채널이 없는 구조에 비해 전력 밀도가 약 165% 향상함을 보였다.

Evaluating the effect of refined flow channels in a developed biomimetic flow field on PEMFC performance

In this study, an improved biomimetic flow field was proposed, and the effects of the number of refined flow channels on the pressure drop, species distribution and performance of the PEMFC were analyzed by numerical simulation. Subsequently, these developed biomimetic flow fields (BIFFs) were compared to the conventional parallel flow field (CPFF) and conventional serpentine flow field (CSFF). The results show that compared with CPFF, the BIFF with ten refined channels (BI-10) offered the benefits of a low-pressure drop, uniform reactant distribution, and higher output power. In addition, BI-10 showed superior heat dissipation compared with CSFF. As the number of refined flow channels increased, the oxygen distribution of the BI-10 became more uniform, and the fuel cell performance also improved. The peak power density of BI-10 was approximately 29.05% higher than that of CPFF and 17.80% higher than that of the original biomimetic flow field (BI-6). In addition, the net power density of BI-10 was similar to that of CSFF; however, BI-10 had a more suitable temperature distribution. Therefore, by increasing the number of refined flow channels, the distribution of reactants was more uniform, the pressure drop was smaller, and the hydrothermal management ability was better.

Dimeric ionic liquid for improving performance and durability of PEMFCs

A dimeric ionic liquid (1,1'-(butane-1,4-diyl)bis9-methylpyrimido[1,2-a]pyrimidinium) di-nonafluorobutanesulfonate (D-MTBD) is investigated for surface modification to a PtCo/C catalyst for improving performance and durability of the catalyst in a fuel cell membrane electrode assembly (MEA). Compared to the PtCo/C catalyst without modification, the addition of the dimeric ionic liquid (IL) improves the mass activity (MA) of the PtCo/C catalyst in the MEA, as well as fuel cell performance. Moreover, the dimeric IL also improves the durability of the PtCo/C catalyst. Thermogravimetry and differential scanning calorimetry were used to evaluate the IL's thermal stability and melting point. The viscosity of the catalyst inks with and without IL were compared. Electrochemically active surface area, impedance, and gas diffusion resistance were evaluated and compared with the PtCo/C catalyst without IL modification. Owing to its higher molecular weight and melting point, the dimeric IL shows potential as a highly stable catalyst modifier. This work shows that the dimeric IL may serve as a replacement to regular monomeric ILs for catalyst surface modification.

Better Electrochemical Performance of PEMFC with a Symmetrical Serpentine Flow Field Bipolar Plate

Better Electrochemical Performance of PEMFC with a Symmetrical Serpentine Flow Field Bipolar Plate

The Role of Porous Carbon Inserts on the Performance of Polymer Electrolyte Membrane Fuel Cells: A Parametric Numerical Study

Herein, for the first time, a computational fluid dynamic study is performed to investigate the effects of using porous carbon inserts (PCI) on the performance of PEMFC. A 3D multiphase multicomponent model is developed to simulate the fuel cell performance. The effects of several geometric and physical parameters of the PCI, including porosity, size, and the arrangement of PCI in the landing area, are numerically examined, which are not investigated in the literature so far. The numerical results showed that using PCI, a 23% improvement in the fuel cell performance is achieved for the optimum case with 80% PCI. In addition, increasing the PCI porosity results in performance enhancement (12.6% improvement when increasing the porosity up to 0.8). Using PCI with different rib/channel width ratios demonstrates that the use of PCI at higher ratios has a more significant effect. When using 34.1% PCI in a case with a ratio of 2:1, the performance increases about 35%. Moreover, a PCI with larger longitudinal size (4 mm compared to 2 mm) shows higher performance enhancement (5.3% compared to 3.5%).

Insights into Degradation of the Membrane-Electrode Assembly Performance in Low-Temperature PEMFC: the Catalyst, the Ionomer, or the Interface?

Here, we report a study on the structural characteristics of membrane electrode assembly (MEA) samples obtained from a low-temperature (LT) polymer electrolyte membrane (PEM) fuel cell (FC) stack subjected to long-term durability testing for ∼18,500 h of nominal operation along with ∼900 on/off cycles accumulated over the operation time, with the total power production being 3.39 kW h/cm2 of MEA and the overall degradation being 87% based on performance loss. The chemical and physical states of the degraded MEAs were investigated through structural characterizations aiming to probe their different components, namely the cathode and anode electrocatalysts, the Nafion ionomer in the catalyst layers (CLs), the gas diffusion layers (GDLs), and the PEM. Surprisingly, X-ray diffraction and electron microscopy studies suggested no significant degradation of the electrocatalysts. Similarly, the cathode and anode GDLs exhibited no significant change in porosity and structure as indicated by BET analysis and helium ion microscopy. Nevertheless, X-ray fluorescence spectroscopy, elemental analysis through a CHNS analyzer, and comprehensive investigations by X-ray photoelectron spectroscopy suggested significant degradation of the Nafion, especially in terms of sulfur content, that is, the abundance of the -SO3- groups responsible for H+ conduction. Hence, the degradation of the Nafion, in both of the CLs and in the PEM, was found to be the principal mechanism for performance degradation, while the Pt/C catalyst degradation in terms of particle size enlargement or mass loss was minimal. The study suggests that under real-life operating conditions, ionomer degradation plays a more significant role than electrocatalyst degradation in LT-PEMFCs, in contrast to many scientific studies under artificial stress conditions. Mitigation of the ionomer degradation must be emphasized as a strategy to improve the PEMFC's durability.

PEMFC performance decay during real-world automotive operation: Evincing degradation mechanisms and heterogeneity of ageing

A long-term dynamic load cycle is performed on state-of-the-art membrane electrode assemblies, aiming to evaluate the degradation mechanisms of Polymer Electrolyte Membrane Fuel Cell under real-world automotive operations. The load cycle, adapted from the stack protocol defined in H2020 ID-FAST European project, includes load, pressure and temperatures cycling. Events that recover the temporary decay are included, specifically procedures classified in short-stops, cold-soaks, long-stops. Operando voltage and current distribution are measured through a segmented hardware, combined to local in-situ electrochemical characterization. Investigation is supported by scanning and transmission electron microscopy analysis, performed at different locations along-the-flow-field. Reversible degradation weights from few to 20 mV and changes local current distribution, mostly at air-inlet, since the dry-out of ionomer. Cycle efficiency decreases of 3%–9%: the largest irreversible performance losses are observed at air-inlet, while middle-region is the least impacted. Cathode catalyst layer and membrane are the most aged components: platinum active surface area drops in 200–400 h, because of electrochemical Ostwald ripening mechanism, and stabilizes around 62%–67% of initial value. Polymer membranes report ageing compatible with mechanical stress that causes localized thinning, increasing hydrogen crossover. Decay of ionomer in the catalyst layer is discussed, which would consistently explain alterations of mass transport resistance.

Predicting Local Transport Phenomena of PEMFC Catalyst Layers Using a Network Approach

A unique network approach has been developed to predict the movement of ions, reactant gas, and water both in the pore and ionomer phase inside a catalyst layer of PEMFC under various operating conditions. Separate networks for each of the catalyst layer reactive transport paths have been generated in the model and transport equations are applied therein. The simulation results provide insight into the coupling between overall PEMFC performance and local phenomena for different catalyst layer properties (porosity, ionomer to carbon ratio, ionomer volume fraction, catalyst loading, etc.), which can work as a guideline for the premanufacturing of catalyst layers and post-manufacturing testing tool.

(Invited) Numerical Simulation Approaches for Understanding Transports Behavior inside Polymer Electrolyte Membrane Fuel Cells

Augmentation of polymer electrolyte membrane (PEM) fuel cell (FC) performance at high current densities, particularly under automotive application, is important to improve the overall power density and to reduce the cost of PEMFC systems. Primarily, the fundamental non-linearity of the equations governing PEMFC performance on a three-dimensional model necessitates iterative solutions. As of now, mass transport over-potential is a major barrier to achieving high performance at a high current density. Experimental investigations of oxygen transport in particular are limited by an inability to resolve the water saturation-dependent properties. The alternative approach to understand and overcome transport resistances, predominantly inside the gas diffusion layer, is to use advanced numerical modeling.Numerical simulation techniques using in PEMFC will be presented including conventional computational fluid dynamics and the meshless Lattice Boltzmann method (LBM) which is an alternative advanced modeling technique [1-14]. This approach can be applied to existing models to visualize the transports inside the structure of microscale geometries, such as: a gas diffusion layer (GDL), micro porous layer (MPL), and catalyst layer (CL). The study where the goal was to use these numerical approaches and directly predict the transports behavior across the length scale (macro-, meso-, micro-, and nano- scales) as shown in Figure 1. The understanding of local kinetic activity inside nanoscale CL implemented into the model will also be discussed. The achievement of this work can enhance the potential capability of a model-based investigation of transport physics inside PEMFC to find solution of designs and operational conditions especially for transport applications.