Cathode Flow Research Articles

A feedback linearization sliding mode decoupling and fuzzy anti-surge compensation based coordinated control approach for PEMFC air supply system

With the application of proton exchange membrane fuel cell (PEMFC) in the field of transportation and energy, the requirements for air flow and pressure tracking performance, efficiency and stability of PEMFC air supply system become higher and higher. To improve PEMFC cathode air flow and pressure control performance under load variation and avoid surge of air compressor, a novel feedback linearization sliding mode decoupling and fuzzy anti-surge compensation based coordinated control approach is proposed. Firstly, optimal references of oxygen excess ratio (OER) and cathode air pressure under different load are calculated based on net output power of PEMFC system analysis. Then, an extended state observer is designed to estimate the cathode air pressure and flow in real time, a feedback linearization sliding mode based decoupling controller is designed to enhance OER and air pressure tracking control performance and robustness. Considering on the operating trajectory and surge line of air compressor, a fuzzy logic based anti-surge compensator is designed to prevent air compressor from surge by compensating both air flow and pressure simultaneously. The proposed control approach is implemented in PEMFC air supply control experiments and the results demonstrates its effectiveness.

Numerical investigation of PEMFC performance enhancement through combined design of anodic fishbone ridge groove channel and optimal gas diffusion layer porosity gradient

The flow field plate is one of the core components of proton exchange membrane fuel cells (PEMFC), and its structure significantly influences the thermo-electrochemical coupling transport characteristics of PEMFCs. Optimizing the parameters of the flow channels of bipolar plates is crucial for enhancing the mass transfer of reacting gas and improving water removal capacity. In this study, an anodal fishbone ridge groove combined flow channel (F-SFC) is designed to enhance the diffusion uniformity of anode hydrogen gas, and a 3D multi-phase model of PEMFC is established using the multiphysics simulation software COMSOL Multiphysics. The F-SFC was compared with traditional bipolar plates featuring symmetric anode and cathode flow channels in terms of overall output performance, and the results are presented. The findings indicate that the F-SFC design achieves an average increase of 28.78% in current density and 21.07% in power density compared to conventional fishbone flow channels. When compared to traditional serpentine flow channels, the F-SFC design shows a 13.5% increase in current density and a 10.42% increase in power density. Furthermore, adding multilayer porosity gradients to gas diffusion layers (GDLs) greatly improves internal mass transfer. A gradient porosity of 0.7, 0.5, and 0.3 along the Z-axis produces a more equal distribution of current density and water concentration on the membrane. This work sheds fresh light on optimizing PEMFC design for increased power density, providing useful theoretical advice for future advances.

Study on the influence characteristics of multi-working condition parameters on membrane electrode type CO2 electrolyzer

The electrochemical conversion of carbon dioxide (CO2) into basic chemicals or carbon-based fuels is a promising new strategy for carbon resource utilization. Within this domain, solid-electrolyte CO2 electrolyzer demonstrate significant potential for the continuous production of pure formic acid solutions. This study, leveraging a 4 cm2 visualization electrolyzer, explores the impact of three working condition parameters on performance: working voltage, gas flow rate, and the intermediate chamber water flow rate. It compares the variations in current density, formic acid concentration, and the distribution of liquid water on the cathode side under different working conditions. The results indicate that the working voltage, current density, and formic acid yield are all positively correlated; overly low gas flow rates can lead to CO2 deficiency and diminished electrolyzer performance; concentration control of the formic acid solution is effectively achieved by adjusting the intermediate chamber water flow rate; and during the electrolyzer reaction process, almost all of the liquid water is positioned at the bends downstream of the cathode flow channel.

Dual functionality of cathode microporous layers: Reducing hydrogen permeation and enhancing performance in proton exchange membrane water electrolyzers

Hydrogen permeation and cell performance are critical factors for the safe and efficient operation of proton exchange membrane (PEM) water electrolysis. In this study, the effects of a cathode microporous layer (MPL) on water transport, hydrogen permeation, and cell performance in a proton exchange membrane water electrolyzer (PEMWE) were investigated. Results reveal that adding an MPL between the catalyst layer (CL) and the porous transport layer (PTL) at the cathode reduces interfacial contact resistance by approximately 60 % under 400 N cm−2, leading to superior performance. The wettability of the MPL plays a crucial role in water transport and hydrogen permeation in PEMWEs. The hydrophobic MPL-P-CB4, which uses polytetrafluoroethylene (PTFE) as a binder with a carbon black (CB) loading of 4 mgCB cm−2, enhances the crossover of water and hydrogen from the cathode to the anode through back diffusion, exceeding the technical safety criterion of 2 vol% H2 in the anode product gas (50 % lower explosion limit) at 2.0 A cm−2. However, the hydrophilic MPL with Nafion ionomers as binders (MPL-N-CB4) facilitates efficient removal of water and hydrogen from the cathode CL to the cathode flow field via capillary pressure, resulting in only 0.2 vol% H2 in O2 at 2.0 A cm−2. Consequently, a hydrophilic MPL is optimal for achieving superior performance and low-hydrogen-crossover in a PEMWE cathode. This study provides valuable insights for designing the PTL/CL interface in next-generation PEMWE cathodes.

Innovative flow field design strategies for performance optimization in polymer electrolyte membrane fuel cells

This study introduces an innovative flow field design methodology that departs from traditional approaches, aiming to simplify design variables and ensure an efficient, automated design process. This methodology integrates topology optimization, the Gray-Scott reaction/diffusion system, and Murray's law to design the flow field layout. We applied this methodology to the flow field design of Polymer Electrolyte Membrane Fuel Cells (PEMFC) bipolar plates. Specifically, the optimal two-dimensional pattern of the PEMFC cathode flow field was achieved by merging topology optimization with the Gray-Scott reaction/diffusion system. Applying Murray's law, an optimal three-dimensional flow field with an unpredictable new pattern was established. The design emphasizes efficient fuel diffusion and reduced flow resistance, validated through experiments. Quantitative comparisons with serpentine and parallel flow fields showed performance differences of approximately 60 mV and 120 mV at a current density of 1.43 A/cm2, respectively. These metrics reflect the impact on mass transfer efficiency under high-power PEMFC operations, serving as critical indicators of flow field effectiveness. Additionally, simulations confirmed an 18-fold reduction in pressure drop compared to the serpentine design. This innovative design process offers advantages that could be incorporated into diverse research areas in the future.

Dynamic performance analysis of proton exchange membrane fuel cell in marine applications

To investigate the dynamic characteristics of proton exchange membrane fuel cells (PEMFCs) on maritime vessels, a lumped-parameter model for the PEMFC systems was developed based on a hybrid vessel propulsion systems model. Simulations and analyses of the dynamic characteristics of PEMFCs were conducted under typical sailing conditions. The results reveal a noticeable hysteresis in the operating temperature of PEMFC stacks during vessel voyages, with a delay of about 25 s, leading to significant overvoltage in activation, ohmic, and concentration differences. Significant variations in vessel loads can cause large fluctuations in the component gas pressures in the cathode and anode flow paths within 16.6–19.8 kPa and 78.57–93.06 kPa, respectively. A comparison of different humidification levels for cathode and anode gases demonstrates that, at the same moment, as the humidification of cathode and anode gases increases from 20 % to 100 %, the water content in the proton membrane increases from 2.29 to 13.47, the ohmic impedance decreases from 1.35 mΩ/cm2 to 0.174 mΩ/cm2, and the overshoot of the fuel cell voltage decreases. The output delay decreases from 25 s to 8 s, enhancing overall fuel cell performance. These findings are significant for optimizing the design, performance, and real-time control of marine PEMFC systems.

A One-Dimensional Computational Model to Identify Operating Conditions and Cathode Flow Channel Dimensions for a Proton Exchange Membrane Fuel Cell

A one-dimensional computational model has been developed that can be used to identify operating conditions for the cathode side of a proton exchange membrane fuel cell such that both the inlet and outlet relative humidity is equal to 100%. By balancing the calculated pressure drop along the cathode side flow channel with the change in molar composition, inlet conditions for the cathode side can be identified with the goal of avoiding channel flooding. The channel length, height, width and the land-to-channel width ratio are input parameters for the model so that it might be used to dimension the cathode flow field. The model can be used to calculate the limiting current density, and we are presenting unprecedented high values as a result of the high pressure drop along the flow channels. Such high current densities can ultimately result in a fuel cell power density beyond the typical value of 1.0–2.0 W/cm2 for automotive fuel cells.

An experimental investigation on the performance of direct methanol fuel cell using new anode and cathode flow field designs

This is a comprehensive study of the DMFC through the introduction of new channel designs. A traditional serpentine design with a rib and channel width of 0.8mm on an area of 50mm×50mm is designated as design-1 and used as the reference channel design. Three other new designs are fabricated and tested in comparison with design-1. A 4-outlet, 1-inlet, 4-zone serpentine with 0.8mm of rib and channel width, is designated as design-2. A 4-outlet, 1-inlet, 4-zone serpentine with a converging channel width is designated as design-3. A 4-outlet, 1-inlet, 4-zone zigzag serpentine with a converging channel width is designated as design-4. The study was done in three stages. The first stage investigates the effect of anode channel designs by fixing the cathode design to design-1 and varying the anode designs from design-1 to design-4. The second stage investigates the effect of cathode designs by fixing the anode design to design-1 and varying the cathode designs from design −1 to −4. The third stage investigates the effect of using the same designs at both the anode and cathode sides. All the stages were tested using three anode flowrates (2,5, and 8mL/min) and three methanol concentrations (1, 2, and 3mol/L). Higher concentrations perform better than lower concentrations while lower flowrates perform better than higher flowrates. The percentage improvement by the new designs in comparison to the reference design is: 142%, 94%, and 136% for the first stage; 74%, 125%, and 40% for the second stage; and 16%, -33% and -45% for the third stage, and the order being design −2, −3 and −4 respectively. Design −3 and −4 underperform in the third stage due to the availability of direct paths that boost methanol crossover when using the same design of anode and cathode. The new designs evacuate the CO2 bubbles and byproduct water faster and more efficiently than the reference design.

Utilizing an Integrated Flow Cathode-Membrane Filtration System for Effective and Continuous Electrochemical Hydrodechlorination.

Pd-based electrodes are recognized to facilitate effective electrochemical hydrodechlorination (EHDC) as a result of their superior capacity for atomic hydrogen (H*) generation. However, challenges such as electrode stability, feasibility of treating complex matrices, and high cost associated with electrode synthesis hinder the application of Pd-based electrodes for EHDC. In this work, we investigated the feasibility of degrading 2,4-dichlorophenol (2,4-DCP) by EHDC employing Pd-loaded activated carbon particles, prepared via a simple wet-impregnation method, as a flow cathode (FC) suspension. Compared to other Pd-based EHDC studies, a much lower Pd loading (0.02-0.08 mg cm-2) was used. Because of the excellent mass transfer in the FC system, almost 100% 2,4-DCP was hydrodechlorinated to phenol within 1 h. The FC system also showed excellent performance in treating complex water matrices (including hardness ion-containing wastewater and various other chlorinated organics such as 2,4-dichlorobenzoic acid and trichloroacetic acid) with a relatively low energy consumption (0.26-1.56 kW h m-3 mg-1 of 2,4-DCP compared to 0.32-7.61 kW h m-3 mg-1 of 2,4-DCP reported by other studies). The FC synthesized here was stable over 36 h of continuous operation, indicating its potential suitability for real-world applications. Employing experimental investigations and mathematical modeling, we further show that hydrodechlorination of 2,4-DCP occurs via interaction with H*, with no role of direct electron transfer and/or HO•-mediated processes in the removal of 2,4-DCP.

Comparison of lifetime performance of PEMFC stacks with two cooling strategies under different humidity

While reducing the size and Pt loading can achieve a lower proton exchange membrane fuel cell (PEMFC) stack cost, it is also very important to focus on the performance changes of the PEMFC stack during the long-term operation. A 3D PtCo catalysts long-term performance model is established in this study, and PEMFC stacks with one cooling unit per cell (1-cell stack) and three cells (3-cell stack) are employed as the computational domains, respectively. The effective area of each cell is 50 cm2, and the changes in current density as well as effective catalytic area of PEMFC stacks with two cooling strategies before and after long-term operation under different humidity conditions are investigated at low Pt loadings. The results show that there are large differences in the output voltage and current density distributions between the three cells due to the poor membrane hydration affected by the non-uniform temperature distribution, although the 3-cell stack can significantly reduce the size. Localized catalyst degradation in both 3-cell and 1-cell stacks is closely related to the geometry of the cathodic flow field, and non-uniform catalyst degradation is found to increase the activation and mass transfer losses and change the distribution of current density within the membrane. In addition, the 3-cell stack is found to perform even better in terms of durability, especially under high humidity conditions, which provides a potential solution to improve the durability of PEMFC stacks operating in harsh conditions.

Efficient Electrochemical Hydrogenation of Furfural to Furfuryl Alcohol Using an Anion-Exchange Membrane Electrolysis Cell.

The electrochemical hydrogenation (ECH) of furfural (FF) offers a promising pathway for the production of furfuryl alcohol (FA) while aligning with sustainability and environmental considerations. However, this technology has primarily been studied in half-cell configurations operating at high cell voltages and low current densities. Herein, we employ a membrane electrode assembly (MEA) system with an anion-exchange membrane for the ECH of FF and systematically investigate various parameters, including the ionomer content in the cathode catalyst, electrolyte type, electrolyte concentration, and flow rate. Under optimal conditions, our MEA system with non-noble metal-based catalysts exhibits a current density of 30 mA cm-2 with a Faradaic efficiency for FA production of 66% at a cell voltage of 2 V, maintaining operational durability for 5 h. This study highlights the potential of electrochemical FA production for practical applications to realize the decarbonization of the hydrogenation industry.

Experimental study of a solid oxide fuel cell afterburner for a 30 kW generator module: A comparative performance analysis

A comprehensive performance test is conducted on a diffusion burner designed for a 30 kW-class methane solid oxide fuel cell (SOFC) power generation system. To facilitate this assessment, a test system is established, capable of simulating the gas composition and temperature of the anode and cathode at the outlet of the fuel cell stack under various typical operating conditions. The test results demonstrate the afterburner's exceptional robustness, minimal pressure loss, and low emission characteristics. Notably, the afterburner can be ignited and started at low load (6LPM, 20 % of the rated methane flow rate) and can achieve low-load heating (4LPM, at approximately 13 % of the rated methane flow rate) with a significant excess air coefficient of 46.2. Remarkably, the afterburner maintains its reignition capability under all operating conditions. Operational stability is observed with a water-to-carbon ratio below 3, displaying robust resistance to fluctuations in water vapor and airflow. Under generating condition, the afterburner exhibits self-ignition capabilities without the need for an external igniter following flameout. The pressure losses within both the anode and cathode flows remain well below 200Pa, while NOx and CO emissions are recorded at 1.7mg/kWh and 66.2mg/kWh, respectively, complying with the stringent EU EN676:2020 standards.

Finite‐time sliding mode fault‐tolerant control of PEM fuel cell air supply system

AbstractProton exchange membrane (PEM) fuel cell air supply system is primarily responsible for delivering air to the fuel cell at a specific stoichiometric ratio for chemical reaction. The stoichiometric ratio will be impacted by the sudden change in load and system failure. Under the aforementioned circumstances, precise and timely air supply regulation is required to avoid irreparable PEM damage. In order to enhance the robustness and performance of the fuel cell, a cascaded finite time sliding mode fault‐tolerant control method is proposed for the air supply system of PEMFC. The control objective is to adjust the oxygen excess ratio at the cathode flow field, which can avoid the occurrence of oxygen starvation in the PEM fuel cell when the load current changes rapidly or when fault occurs. A cascaded controller structure is introduced, where, in the inner loop, an adaptive sliding mode controller is designed to reconstruct fault signal and track the optimal output trajectory and, in the outer loop, a finite‐time observer is employed to obtain the expected output trajectory. The proposed control scheme is capable of fault‐tolerant tracking of the optimal oxygen excess ratio within finite time. The effectiveness of proposed fault‐tolerant control algorithm is verified through hardware‐in‐the‐loop (HIL) studies.

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.

Understanding water dynamics in operating fuel cells by operando neutron tomography: investigation of different flow field designs

Water management plays a key role in ensuring optimum polymer electrolyte fuel cell (PEFC) performance, and flow field design can influence the ability of a cell to balance maintaining hydration, whilst avoiding flooding and cell failure. This work deepens the understanding of water evolution in different PEFC flow channel designs, namely single serpentine (SS), double serpentine (DS) and parallel, using our novel high-speed neutron computed tomography method. We developed our previously-reported method by introducing continuous cell rotation, enabling 18 s per tomogram during 1 h holds at 300, 400 and 500 mA cm−2. The volume of water evolved in the cathode, membrane electrode assembly and anode was quantified, and key mechanisms for water droplet formation in the different flow channel designs were elucidated. The parallel flow field design had the poorest water management, with 47% of the cathode flow channel becoming filled after 1 h at 400 mA cm−2. This significant flooding blocked reactant sites and contributed to unstable cell performance and, ultimately, cell failure at higher current densities. The SS cell displayed the best water management, with only 11% of the cathode channel filled with water after 1 h at 500 mA cm−2, compared with 28% of the DS cathode channel. 3D visualisation and analysis of droplet behaviour elucidated how water ‘slugs’ in the SS were removed in the gas stream, whereas three of the four parallel cathode flow channels became entirely filled with water plugs, blocking gas flow and exacerbating cell flooding. The new insights gained here are expected to extend to novel flow field designs and image-based models, with the use of operando neutron CT demonstrated as a powerful technique for both visualising and quantifying water management in operating PEFCs, as well as deepening the knowledge of droplet behaviour in different flow field types.

Performance evaluation of cathode channels with different cross-sections for open-cathode polymer electrolyte membrane fuel cell stack

This study proposes six different cross-sectional cathode flow field designs such as square, trapezoid, dome, boot, pentagon, and triangular constructing four cells open cathode polymer electrolyte membrane fuel cell stack with various parameters optimization and suitability for system level development. Parameters, including pressure drop, oxygen concentration, airflow rate, blower power, stack temperature, cooling rates, net power output, and stability are investigated with focus on understanding the trend, interconnected dependencies among the parameters, which collectively influence the overall performance of the cross-section designs. Overall, studies show that, boot cross-section design possessing the optimum pressure drop of 23.9 Pa, shows better performance compared to other cross-section designs due to better oxygen gas distribution, water retention/removal, heat removal/retention, and net power output. Conversely, for galvanostatic analysis done at a higher current value of 35 A, dome and square cross-section designs show highest and stable potential, along with balanced stack temperature.

Effects of channel structure at inlet region on temperature distribution of proton exchange membrane fuel cells

Enhancing the temperature distribution uniformity in membrane electrodes is crucial for improving the durability and performance stability of proton exchange membrane fuel cells. In this study, we discovered an entrance region in the cathode membrane electrode of proton exchange membrane fuel cells characterized by a rapid rise in temperature. This inlet region shows a notably higher temperature variation rate compared to other regions. This phenomenon is attributed to the temperature difference between the constant temperature fluid supplied by the channel inlet and the heat generation in the cathode catalyst layer. Thus, the impact of channel structure at the entrance region on the temperature distribution of the cathode catalyst layer is investigated, based on a three-dimensional, non-isothermal, two-phase model. Results show that boosting heat transfer in the inlet region is more effective for reducing the average temperature than in other regions. We proposed five kinds of step arrangement schemes and discovered that the step arrangement in the entrance region of the cathode flow channel can increase the temperature uniformity of the cathode catalyst layer by 9.71% without net power loss. Furthermore, this study examines the impact of length, height of entrance steps, and outlet channel height on heat transfer and identifies the optimum value. When severe water flooding occurs, the gas purge coupled with the step-fronted scheme is essential for improving temperature uniformity.

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.

Advanced design of cathode array protrusion structure of solid oxide fuel cell based on NSGA-II multi-objective optimization

As fuel cells gain widespread utilization, augmenting the power density and combination property of Solid Oxide Fuel Cells (SOFCs) has emerged as a pivotal area of research. This study introduces an innovative arrayed protrusion structure within the cathode flow channels of SOFCs to induce secondary flow. The influence of this arrayed structure on fuel cell combination property is meticulously analyzed through comprehensive numerical simulations. Furthermore, this paper employs the Response Surface Methodology to evaluate the synergistic effects of cathode operational conditions, particularly temperature, and arrayed structure parameters (including base width, height, and quantity) on SOFC performance. Correlations among these variables have been established to show synergistic associations between variables and performance index. The findings reveal that the inclusion of an arrayed structure in the cathode flow channels generates multi-directional vortices, thereby intensifying gas disturbance, facilitating reactant diffusion, and optimizing oxygen concentration distribution. This results in a marked enhancement of the fuel cell's overall performance. Among the operational parameters analyzed, temperature exerts the most substantial influence on power density, followed by protrusion height, base width, and number. Ultimately, using the Non-dominated Sorting Genetic Algorithm-II (NSGA-II), Pareto optimal solutions were derived, yielding a superior balance of higher power density and reduced pressure drop. Compared to the baseline, the power density in these Pareto optimal solutions saw an increase of 16.5% to 23.6%, while pressure drop escalated marginally by 1.5% to 8.9%.

Temperature distribution evolution in zero-gap alkaline water electrolyzer: Experimental and modeling

Alkaline water electrolysis technology is currently the most prospective commercial choice for producing green hydrogen, however, accurately modeling the temperature distribution evolution inside the alkaline water electrolyzer is still a challenge, since the existence of strong coupling multi-physical fields among gas–liquid flow, electrochemistry and heat transfer. In this article, 3D simulation models of the zero-gap alkaline water electrolyzer are established considering the mutual coupling relationship among two-phase flow, electrochemistry and heat transfer as well as the bypass current effect to study the heat transfer property and temperature profiles under different electrolysis conditions. The simulation study is conducted for the electrolyzer consisting of five electrolysis cells. The voltage, temperature difference and gas production rate were measured experimentally and simulated well using the established models. It indicates that the average relative error is respectively 0.45% for the estimated cell voltage, 13% for the estimated outlet-inlet temperature difference of the cathode flow channel, and 1.18% for the estimated hydrogen production rate. The characteristics of temperature distribution evolution in the zero-gap alkaline water electrolyzer have been disclosed, accordingly the suitable heat management strategy has been suggested for the stable operation. The results would provide a useful guide on the optimization and design of large-scale alkaline water electrolyzer to implement long-term stable operation with low cost.