Temperature Proton Exchange Membrane Fuel Research Articles

Investigation of Ceria based Heterostructure Composite Mixed Matrix Membrane with Polybenzimidazole for Polymer Electrolyte Fuel Cell Application at High Temperature

In recent years Ceria based heterostructure composites are considered as one of the highest performing solid state ionic conductors, therefore we wanted to leverage the benefits of using these materials for high temperature Proton Exchange Membrane Fuel Cells (PEMFCs). In this study a Polybenzimidazole (PBI)/Ceria carbonate CHC (Ceria based heterostructure composite) membrane was prepared by drop casting method and tested as an electrolyte for a high temperature H2/Air PEMFC application in anhydrous condition. Inorganic composite of ceria and alkali metal carbonates (Li2CO3, Na2CO3) was prepared by solid state route to obtain Ceria carbonate CHC. X-Ray diffraction (XRD) study confirmed the formation of the heterostructure and their successful incorporation into the PBI membranes. Homogeneity of fillers inside the membrane was further verified by Energy Dispersive X-Ray Analysis (EDAX) and Scanning Electron Microscopy (SEM). 5wt% of inorganic powder induced inside the PBI fillers reduced the phosphoric acid uptake of composite membrane (∼17% less) compared to pristine PBI membrane, which ultimately resulted into a lower swelling and dimensional change of the composite membrane. Thermal robustness of the phosphoric acid doped composite and pristine PBI membranes was investigated by thermogravimetric analysis (TGA) which showed that the prepared membranes were gone under a less than 10% reduction in weight up till 200ºC, ensuring their validity of application in high temp PEM fuel cells. The added inorganic functionalities resulted in a slight increase in the proton conductivity of PA doped composite PBI membranes i.e., 42.3 mS cm-1 at 180 ºC while for pristine PBI membrane it is 36 mS cm-1 at same temperature. A single cell with composite PBI membranes outperformed a pristine PBI membrane resulted into a ∼120% higher peak power density i.e., 320.88 mW cm-2. The composite membrane also displayed the excellent durability and showed a less than 10-4 mV/h degradation in cell potential till 180 ºC.

Experimental Investigation on the Backpressure Effect on the Performance of a High Temperature Proton Exchange Membrane Fuel Cell Stack

This study investigated the impact of backpressure of anode and cathode on the performance of a high-temperature proton exchange membrane fuel cell stack consisting of 30 cells, initially operating at a current density of 0.4 A/cm², temperature of 160 ℃, and 0 bar with pure H2. Subsequently, the backpressure on both sides was varied from 0 bar to 1.5 bar, and the changes in stack performance were recorded throughout the testing period. Additionally, the impact of backpressure was also investigated with reformates (H2/CO2/CO/N2 = 69.4%/22.3%/1.40%/6.9%) as anode feed for the stack. The results showed that increase in operating backpressure improves the fuel cell performance. A stack voltage increase of 20 mV per cell and 40 mV per cell were achieved for the pure hydrogen operation and reformate gas operation respectively when increasing backpressure from 0 bar to 0.5 bar. This signifies potential to improve the system’s overall efficiency with only minor penalty in terms of auxiliary power loss to increase the back pressure.

Experimental Investigation on the Backpressure Effect on the Performance of a High Temperature Proton Exchange Membrane Fuel Cell Stack

This study investigated the impact of backpressure of anode and cathode on the performance of a high-temperature proton exchange membrane fuel cell stack consisting of 30 cells, initially operating at a current density of 0.4 A/cm², temperature of 160 ℃, and 0 bar with pure H2. Subsequently, the backpressure on both sides was varied from 0 bar to 1.5 bar, and the changes in stack performance were recorded throughout the testing period. Additionally, the impact of backpressure was also investigated with reformates (H2/CO2/CO/N2 = 69.4%/22.3%/1.40%/6.9%) as anode feed for the stack. The results showed that increase in operating backpressure improves the fuel cell performance. A stack voltage increase of 20 mV per cell and 40 mV per cell were achieved for the pure hydrogen operation and reformate gas operation respectively when increasing backpressure from 0 bar to 0.5 bar. This signifies potential to improve the system’s overall efficiency with only minor penalty in terms of auxiliary power loss to increase the back pressure.

Ionomeric Binders for High Temperature Proton Exchange Membrane Fuel Cells.

High-temperature proton exchange membrane fuel cell (HT-PEMFC) based on phosphoric acid doped polybenzimidazole membrane (PBI/PA) operating at 120-200 °C can provide insensitivity to carbon monoxide (CO) and simplified managements of water and heat and thus attract significant global attention. However, one significant drawback is its low utilization of precious metal catalysts resulted from the PA poisoning and inefficient three-phase boundary. Studies of binder materials in catalyst layers for HT-PEMFC are gradually emerging and there are few literature reviews on this important topic. The purpose of this review is to describe the various types of binders based on their molecular structure and electrochemical properties, with particular emphasis on catalyst layer for fuel cells. Importantly, this review provides a better understanding of relationship between fuel cell performance and the gas permeability and conductivity of different binders. Then, future directions of research and development in binder materials of HT-PEMFC are pointed out.

An Air Over-Stoichiometry Dependent Voltage Model for HT-PEMFC MEAs

In this work, three commercially available Membrane Electrode Assemblies (MEAs) from Advent Technology Inc. and Danish Power Systems, developed for a use in High Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC), were tested under various Operating Conditions (OCs): over-stoichiometry of hydrogen gas (1.05, 1.2, 1.35), over-stoichiometry of air gas (1.5, 2, 2.5), gas oxidant (O2 or air) and temperature (140 °C, 160 °C, 180 °C). For each set of operating conditions, a polarization curve (V–I curve) was performed. A semi-empirical and macroscopic (0D) model of the fuel cell voltage was established in steady state conditions in order to model some of these experimental data. The proposed parameterization approach for this model (called here the “multi-VI” approach) is based on the sensitivity to the operating conditions specific to each involved physicochemical phenomenon. According to this method, only one set of parameters is used in order to model all the experimental curves (optimization is performed simultaneously on all curves). A model depending on air over-stoichiometry was developed. The main objective is to validate a simple (0D) and fast-running model that considers the impact of air over-stoichiometry on cell voltage regarding all commercially available MEAs. The obtained results are satisfying with AdventPBI MEA and Danish Power Systems MEA: an average error less than 1.5% and a maximum error around 15% between modelled and measured voltages with only nine parameters to identify. However, the model was not as adapted to Advent TPS® MEA: average error and maximum error around 4% and 21%, respectively. Most of the obtained parameters appear consistent regardless of the OCs. The predictability of the model was also validated in the explored domain during the sensibility study with an interesting accuracy for 27 OCs after being trained on only nine curves. This is attractive for industrial application, since it reduces the number of experiments, hence the cost of model development, and is potentially applicable to all commercial HT-PEMFC MEAs.

Perspectives on Membrane Development for High Temperature Proton Exchange Membrane Fuel Cells

Perspectives on Membrane Development for High Temperature Proton Exchange Membrane Fuel Cells

Modeling and Simulation of a High Temperature Proton Exchange Membrane Fuel Cell

High temperature (HT) (around 120-200°C) PEM FCs are predicted to be the next generation of PEMFCs particularly for hydrogen-powered automobiles and combined heat and power (CHP) systems because the water management can be simplified at such temperatures as only a single phase of water vapor needs to be considered. Additionally, the cooling system can be streamlined due to an increase in temperature gradient between the coolant and the FC stack. This will also allow easy recovery of waste heat that can be used as a practical heat source. Furthermore, the CO tolerance improves dramatically at high temperatures thereby allowing HT PEMFCs to utilize reformed and impure hydrogen.A single phase three-dimensional, steady-state, isothermal model for a single 5 HT PEM fuel cell with serpentine flow channels is implemented in COMSOL to investigate the effect of various operating conditions like temperature, back pressure and cathode flow rate and design parameters like catalyst layer loading, cathode GDL porosity, and flow field channels including parallel and interdigitated channels. Different performance indicators in terms of polarization curve, loss mechanisms, oxygen molar concentration, and anode and cathode pressure are represented for a complete overall analysis. In fact, the breakdown of different overpotential loss mechanism for HT PEMFC presented here is unique that not only quantifies these losses but also provides an accurate comparison with corresponding low temperature counterpart. The result from the computational model follows the experimental result very closely, thus, validating our model. The simulations stipulates that the performance of a HT PEMFC improves with increasing temperature, back pressure, and air flow rate. Increasing catalyst layer loading improves the performance up to a point after which it starts to drop at low voltages because of hindered gas diffusion. Similarly, a comparative study among different flow field channel is also presented indicating improved performance when going from parallel to interdigitated and serpentine channels. Furthermore, this study provides guidelines to optimize HT PEMFC performance through comprehensive parametric study.

Study on Synthesis of Polybenzimidazole (PBI) Using Low Cost & High Impurity Industrial 3,3'-diaminobenzidine (DAB) for Application in High Temperature Proton Exchange Membrane Fuel Cells

Poly[2,2-(m-phenylene)−5,5-bibenzimidazole] (m-PBI), the most studied PBI, is close to practical application, however, the high cost of m-PBI restricts its application for HT-PEMFCs. The cost can be reduced by 85% if the low cost & high impurity industrial DAB can be used to synthesize m-PBI after pre-treatment. Herein, we study the influence of impurities in industrial 3,3′-diaminobenzidine (DAB) on the synthesis of polybenzimidazole (PBI), and the possibility of the synthesis of m-PBI based on purified low cost & high impurity industrial DAB. It is shown that impurities would reduce the molecular weight and thermal stability of PBI, and mechanical strength and oxidation stability of the according PBI and H3PO4/PBI membranes. Using industrial DAB (94.40%) without any treatment as a reactant, the molecular weight of the obtained PBI is too low to prepare a membrane. A simple method of purifying low cost & high impurity industrial DAB is proposed, by dissolution and recrystallization using the absorption effect of carbon powder. It is proven that the performances of PBI synthesized using purified DAB are near to the PBI synthesized using high-purity DAB. The peak power density of HT-PEMFC based on PBI from purified industrial DAB reached 426 mW cm−2 at 180 °C.

Numerical Analysis on the Effect of Stoichiometric Ratio on Fuel Utilization and Performance of High Temperature Proton Exchange Membrane Fuel Cells

Numerical Analysis on the Effect of Stoichiometric Ratio on Fuel Utilization and Performance of High Temperature Proton Exchange Membrane Fuel Cells

Numerical Study on Thermal Stress of High Temperature Proton Exchange Membrane Fuel Cells during Start-Up Process

High-temperature proton-exchange membrane fuel cells (HT-PEMFCs) with phosphoric-doped polybenzimidazole (PBI) membranes have a higher operating temperature compared to the PEMFCs operating below 373.15 K. The fuel cell is first heated from room temperature to the minimum operating temperature to avoid the generation of liquid water. The existence of liquid water can result in the loss of phosphoric acid and then affect the cell performance. In this study, the start-up process of HT-PEMFCs is numerically studied by establishing a three-dimensional non-isothermal mathematical model. Preheated gas is supplied into gas flow channels to heat the fuel cell, and then voltage load is applied to accelerate the start-up process. Effects of voltage (0.9 V, 0.7 V and 0.5 V) and flow arrangement (co-flow and counter flow) on temperature, current density, proton conductivity and stress distributions of fuel cells are examined. It is found that the maximum stress is increased when a lower voltage is adopted, and the counter-flow arrangement provides a more uniform stress distribution than that of co-flow arrangement.

Towards the Reduction of Pt Loading in High Temperature Proton Exchange Membrane Fuel Cells - Effect of Fe-N-C in Pt-Alloy Cathodes.

Pt poisoning by phosphate in high temperature proton exchange membrane fuel cells (HT-PEMFC) leads to loadings up to 1 mgPt cm-2 per electrode of costly materials. While cheaper Fe-N-C catalysts are unaffected by phosphate deactivation and contribute to the catalysis of the oxygen reduction reaction, their volumetric activity is substantially lower. In this study, the effect of Pt-loading reduced hybrid cathodes for HT-PEMFC is investigated using commercial Celtec®-P-based assembling. A promising effect of Fe-N-C incorporation in terms of acid attraction and activity retention is found. A longer activation (230 h, 0.3 A cm-2 ) for the hybrid membrane electrode assembly (MEA) is necessary, due to the slower acid distribution within Fe-N-Cs. This study shows the potential of Pt-content reduction by up to 25 % compared to standard MEA using hybrid electrodes. Moreover, important insights for future strategies of cell activation are revealed for these hybrid MEAs.

Experimental study of the potential degradation due to the polarization curve of a high temperature proton exchange membrane fuel cell

The polarization curve is the most common characterization used to describe the steady-state of a fuel cell. The methods proposed in the literature to realize polarization curves for High Temperature Proton Exchange Membrane Fuel Cells (HT-PEMFC) are mainly focused on ensuring stable operating conditions. However, if degradations are caused during its realization, the interpretation of the experimental results may be biased. In order to understand and highlight these different phenomena, an experimental campaign is carried out on Advent PBI (formerly BASF Celtec®-P 1100W) membrane-electrode assemblies (MEA). Four different methodologies for the realization of polarization curves including impedance spectroscopies are proposed. Each one is cycled 30 times in order to compare their impact on fuel cell degradation. The use of a CO2 sensor confirms that carbon corrosion is the main degradation caused by the passage to high voltage. Moreover, the analysis shows that this degradation can be intensified according to the conditions preceding the switch to these voltages. However, the realization of a current truncated polarization curve in order to avoid this degradation can be at the origin of the generation of reversible losses which can distort the interpretation of the results. The atmospheric pressure variation also generates a bias as the polarization curves are not necessarily realized at the same value because the gas outlet pressures are not regulated. A methodology of voltage readjustment according to the operating conditions is thus applied in order to compensate for this effect. Finally, the cycling of one of the polarization curve realization methods shows an interest for improvingthe break-in period.

Modeling of Packed Bed Methanol Steam Reformer Integrated with Tubular High Temperature Proton Exchange Membrane Fuel Cell

Modeling of Packed Bed Methanol Steam Reformer Integrated with Tubular High Temperature Proton Exchange Membrane Fuel Cell

Analyses of the Effects of Electrolyte and Electrode Thickness on High Temperature Proton Exchange Membrane Fuel Cell (H-TPEMFC) Quality.

Researchers have been striving to minimize proton exchange membrane fuel cell components thickness. This is believed to reduce the losses (active losses, ohmic losses and mass transfer losses) associated with this cell. In this study, we numerically analyze the electrodes and electrolyte thickness effects on high-temperature proton exchange membrane fuel cell (H-TPEMFC) performance. COMSOL Multiphysics is adopted to model both the impedance spectroscopy and polarization of the cell. Increased cell catalyst layer (thick electrode) improves the overall cell performance by ±10%, because of the improved reaction rate. It presents 0.89 mol m-3 lesser oxygen compared to that of the thin electrode cell. On the contrary, thick cell electrodes come with increased mass transport loss. The high reaction rate is also confirmed by the high amount of generated water, which is 0.42 mol m-3 higher than that of thin electrode cell. The experiment used to set the modeling parameter renders results with only less than 5% discrepancy to the modeling results. Also revealed is that over a limited range, electrolytes thickness variation has negligible effects on H-TPEMFC performance.

CFD simulation of water droplet adhesion on the GDL of a low temperature PEM FC in air cross-flow conditions

Water management is a critical challenge in low temperature (LT) Proton Exchange Membrane Fuel Cells (PEM FC); condensed liquid appears mainly at the cathode side, where water from the reduction reaction is generated. Differences in concentration may result in the transfer of water to the anode side across the membrane electrode assembly (MEA). Excessive liquid can negatively affect fuel cell performance, causing low efficiency and instability. This occurs due to water movement through porous layers and channels that are the essential pathways for the reactant gas to reach the MEA. However, water is necessary in the PEM FC for enhancing ion conductivity of the membrane. The present study can contribute to the optimization of LT PEM FCs by analysing the water behaviour under flow conditions. The widely used Volume Of Fluid (VOF) method is adopted for simulating multiphase flow. CFD simulation of droplet adhesion on the gas diffusion layer (GDL) is performed to describe the interaction between water and gas flow. Deformation and oscillations of droplets with diameters in the 0.3-1.0 mm range are investigated by considering airflow rates up to 15.0 m/s. CFD analysis is validated by optical data from digital imaging with high spatial (up to 5.8 μm/pixel) and temporal (up to 1.0 ms) resolution.

(Invited) Catalyst Challenges for Ion-Pair High Temperature Proton Exchange Membrane Fuel Cells

High temperature proton exchange membrane fuel cells (HT-PEMFCs) have several merits over low temperature PEMFCs, including simplified fuel cell systems and high CO tolerance. Recently developed ion-pair HT-PEMFCs1 has a significantly lower concentration of phosphoric acids in the membrane-electrode assembly (MEA) that allows ion-conducting binders (ionomers) in the electrodes. Here, we first explain the difference in MEA configurations and fuel cell performance between conventional polybenzimidazole-based and ion-pair HT-PEMFCs2. Next, we discuss catalyst challenges for ion-pair HT-PEMFCs by comparing half-cell and single-cell results.We focus on three critical areas in that electrocatalysts face challenges: i) phosphate anion poisoning on oxygen reduction reaction catalysts, ii) phenyl adsorption on hydrogen oxidation reaction catalysts and iii) phosphoric acid flooding. Research progress mitigating those adverse effects is demonstrated using various commercial Pt-based catalysts and homemade ionomers. Lastly, we provide general directions for designing high-performing catalysts of ion-pair HT-PEMFCs.References Lee, K. S.; Spendelow, J. S.; Choe, Y. K. Fujimoto, C.; Kim, Y. S. An Operationally Flexible Fuel Cell Based on Quaternary Ammonium-Biphosphate Ion Pairs, Nature Energy, 1, 16120 (2016).Lim, K. H.; Lee, A. S.; Atanasov, V.; Kerres, J.; Park, E. J.; Adhikari, S.; Maurya, S.; Manriquez, L. D.; Jung, J.; Fujimoto, C.; Matanovic, I.; Jankovic, J.; Hu, Z.; Jia, H.; Kim, Y. S. Protonated phosphonic acid electrodes for high power heavy-duty vehicle fuel cells, Nature Energy, 7, 248 (2022).

Experimental and Numerical Analysis of Low Temperature Proton Exchange Membrane Fuel Cell (PEMFC) with Different Fuel Flow Rate in Improving Fuel Cell Performance

The PEM fuel cell was examined using numerical simulation in varied circumstances. To restore the fuel cell performance, a 3D-based PEMFC model was designed employing COMSOL Multiphysics 5.1. The analysis validity was confirmed using the V-I curves derived from data analysis in varied operational circumstances. The continuity, momentum, species transport and charge equations were used to represent the cell transport phenomenon. The flow of permeable medium in the gas diffusion layer was defined by employing Brinkman equations. V-I curves were obtained using the Butler-Volmer equations. According to findings, the current supply in the cathode catalyst layer achieves an optimum one, functioning as mass transport, ionic and charge transport resistances. It indicates optimum current supply in the cell holds a feature of highest oxygen deprivation on the channel's output side.

Real-Time Monitoring of the Temperature, Flow, and Pressure Inside High-Temperature Proton Exchange Membrane Fuel Cells.

The proton exchange membrane fuel cell (PEMFC) system is a highly efficient and environmentally friendly energy conversion technology. However, the local temperature, flow, and pressure inhomogeneity within the fuel cell during the electrochemical reaction process may lead to depletion of PEMFC material and uneven fuel distribution, thus affecting the performance and service life of high-temperature PEMFCs. In this study, micromachining technology is used to develop a three-in-one flexible micro-sensor that is resistant to a high-temperature electrochemical environment (120~200 °C). Appropriate materials and process parameters are used to protect the micro-sensor from failure or damage under long-term testing, and to conduct a real-time micro-monitor of the local temperature, flow, and pressure distribution inside high-temperature PEMFCs.

A Review on Temperature Reduction Management and Heat Management System to be Implemented in High Temperature Proton Exchange Membrane Fuel Cell

Commercialization of technology of PEMFC (proton electron membrane fuel cells) remains a big obstacle regardless of the broad research on PEM and other fuel cells.High temperature proton exchange fuel cell has found its wide application now days and it is very important to manage the Heat and apply cooling arrangement for the fuel cell stack as durability is at stake when exposed for the longer duration. Considering the heat sources HT-PEM has three heat sources: 1) irreversible joule heating caused by the charge transport in the solid electrolyte or the conductor 2) Reversible heating due to the charge entropy change and 3) irreversible heating of the reaction caused due to the over potential. Considering all the aspect it is found that the optimum temperature for HT PEM Fuel cell is 170℃ to 180℃ though it is observed that at 200℃ the efficiency has shown positive effect. The enormous heat generated by the electrochemical reaction of the fuel cell as a by-product and when it reaches to the extreme limit of the recommended temperature which makes cooling necessary and based on the FC power the cooling strategy is to be implemented accordingly, Even though there are many methods for cooling but the medium through which the cooling takes place is restricted to 2 i.e. Air and Liquid..

Comparative Study of Different Activation Procedures of High Temperature Proton Exchange Membrane Fuel Cells

Herein, the objective is to investigate the activation mechanism and activation process in high‐temperature proton exchange membrane fuel cell under different activation procedures from multiple perspectives. The effects of galvanostatic, temperature cycling, current step cycling, and increasing back pressure on cell performance were investigated by current density distribution test, electrochemical impedance spectroscopy, and distribution of relaxation times analysis. The results show that galvanostatic activation was the optimal activation mode. Current step cycling and elevating back pressure activation increase the voltage growth rate, but make the difference in the optimization of each parameter become greater, and do harm to cell performance stability and long‐term durability. Temperature cycling activation increases the charge transfer resistance and makes the uniformity of current density distribution deteriorate due to the thermal and mechanical stresses. It emphasizes the fact that different activation modes had great influence on the uniformity of current density distribution, and the optimization speed and change trend of each key parameter are not synchronized during the activation process. It is insufficient to focus only on voltage reaching steady state, and factors such as voltage, impedance, and uniformity of current density distribution should be considered comprehensively.