High-Temperature Proton Exchange Membrane Fuel Research Articles

Design, modeling, and optimization of a novel 6 kWe hybrid solid oxide fuel cell high temperature-proton exchange membrane fuel cell system

This work investigates a novel approach in terms of design, configuration, heat integration and optimization of a 6 kWe total energy system fueled with natural gas. Specifically, a Solid Oxide Fuel Cell (SOFC) is used for both electricity generation and fuel reforming, since its exhaust stream fuels a polybenzimidazole (PBI)-based, High Temperature-Proton Exchange Membrane Fuel Cell (HT-PEMFC). The study investigates the possible advantages of such a system in both technical and economic terms. After modeling each component/subsystem, the total system model is optimized with the objective function aiming to maximize the net electrical efficiency of the total hybrid system. The system is optimized with a genetic algorithm-based optimization strategy, reaching a net electrical efficiency of 43.6 %. In comparison to standalone fuel cell systems with the same net electrical power output, the proposed hybrid system outperforms both an HT-PEMFC system and an SOFC system, which perform at net electrical efficiencies of 23.2 % and 40.7 %, respectively. Also, the lifecycle cost for the proposed system is $64,097, which is lower than both standalone HT-PEMFC and SOFC systems. Therefore, with the current high rising costs for natural gas, such highly efficient systems are likely to become important elements of the future energy infrastructure.

Influence of the Polymer Precursor Structure on the Porosity of Carbon Nanofibers: Application as Electrode in High-Temperature Proton Exchange Membrane Fuel Cells

Influence of the Polymer Precursor Structure on the Porosity of Carbon Nanofibers: Application as Electrode in High-Temperature Proton Exchange Membrane Fuel Cells

Grafting of Amine End-Functionalized Side-Chain Polybenzimidazole Acid-Base Membrane with Enhanced Phosphoric Acid Retention Ability for High-Temperature Proton Exchange Membrane Fuel Cells.

A high phosphoric acid uptake and retention capacity are crucial for the high performance and stable operation of phosphoric acid/polybenzimidazole (PA/PBI)-based high-temperature proton exchange membranes. In this work, amine end-functionalized side-chain grafted PBI (AGPBI) with different grafting degrees are synthesized to enhance both the phosphoric acid uptake and the acid retention ability of the accordingly formed membranes. The optimized acid-base membrane exhibits a PA uptake of 374.4% and an anhydrous proton conductivity of 0.067 S cm-1 at 160 °C, with the remaining proton conductivity percentages of 91.0% after a 100 h stability test. The accordingly fabricated membrane electrode assembly deliver peak power densities of 0.407 and 0.638 W cm-2 under backpressure of 0 and 200 kPa, which are significantly higher than 0.305 and 0.477 W cm-2 for the phosphoric acid-doped unmodified PBI membrane under the same conditions.

Impact of Nonuniform Platinum Loading Distribution Design in the Catalyst Layer on the High-Temperature Proton Exchange Membrane Fuel Cell Performance

Impact of Nonuniform Platinum Loading Distribution Design in the Catalyst Layer on the High-Temperature Proton Exchange Membrane Fuel Cell Performance

Multi-Objective Assessment and Optimization of a High-Temperature Proton Exchange Membrane Fuel Cell: Steady-State Analysis

The design and operational conditions of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) substantially impact their performance. This model aims to investigate the influence of various parameters on the performance of HT-PEMFC. A comprehensive examination revealed that the performance of HT-PEMFC experienced a significant enhancement through modifications to the operating temperature, doping levels, and membrane thickness. Significantly, it can be observed that operating pressure showed a limited influence on performance. The HT-PEMFC was optimized using the non-dominated sorting genetic algorithm II (NSGA-II), specifically emphasizing three primary performance indicators: equivalent power density, energy efficiency, and exergy efficiency. The findings demonstrate promising outcomes, as they reveal a noteworthy enhancement in power density by 17.72% and improvements in energy efficiency and exergy efficiency by 21.11% and 10.37%, respectively, compared to the baseline case.

Guanidinium/Hydroxyl-Functionalized Polybenzimidazole for High-Temperature Proton Exchange Membrane Fuel Cell Applications

Guanidinium/Hydroxyl-Functionalized Polybenzimidazole for High-Temperature Proton Exchange Membrane Fuel Cell Applications

Insights into Oxygen Mass Transport Mechanisms in High-Temperature Proton Exchange Membrane Fuel Cells with Microelectrode

The mass transport of oxygen in the cathode catalyst layer of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) has a great impact on cell performance. However, some bulk average methods are unable to study the permeation properties of oxygen near the triple phase boundary of HT-PEMFCs due to the size mismatch. Here, we develop a microelectrode integrated system to quantitatively study the O2 mass transport behavior at the Pt/binder interface under actual operating temperatures (100 °C–180 °C). The oxygen diffusion coefficients and solubility obtain from potential-step chronoamperometry and a modified Cottrell equation follow the diffusion “ball-cage” model and the dual-mode solubility model. Subsequently, molecular dynamics simulations are used to describe the key structural elements and diffusion behavior of oxygen molecules from the microscopic perspective. These results provide a scientific approach to study the mass transfer process of oxygen at the local environment, endowing with insightful strategies for future improvement and applications of HT-PEMFCs.

Experimental Analysis of Catalyst Layer Operation in a High-Temperature Proton Exchange Membrane Fuel Cell by Electrochemical Impedance Spectroscopy

High-temperature proton exchange membrane fuel cells (HT-PEMFC) directly convert hydrogen and oxygen to produce electric power at a temperature significantly higher than conventional low-temperature fuel cells. This achievement is due to the use of a phosphoric acid-doped polybenzimidazole membrane that can safely operate up to 200 °C. PBI-based HT-PEMFCs suffer severe performance limitations, despite the expectation that a higher operating temperature should positively impact both fuel cell efficiency and power density, e.g., improved ORR electrocatalyst activity or absence of liquid water flooding. These limitations must be overcome to comply with the requirements in mobility and stationary applications. In this work a systematic analysis of an HT-PEMFC is performed by means of electrochemical impedance spectroscopy (EIS), aiming to individuate the contributions of components, isolate physical phenomena, and understand the role of the operating conditions. The EIS analysis indicates that increases in both the charge transfer and mass transport impedances in the spectrum are negatively impacted by air humidification and consistently introduce a loss in performance. These findings suggest that water vapor reduces phosphoric acid density, which in turn leads to liquid flooding of the catalyst layers and increases the poisoning of the electrocatalyst by phosphoric acid anions, thus hindering performance.

Performance, Efficiency, and Flexibility Analysis of a High-Temperature Proton Exchange Membrane Fuel Cell-Based Micro-Combined Heat-and-Power System with Intensification of the Steam Methane Reforming Step by Using a Millistructured Reactor.

The complete simulation model of an existing 1 kW high-temperature proton exchange membrane (HT-PEM) fuel cell-based residential micro-combined heat-and-power process, including a compact intensified heat-exchanger-reactor, is developed in the simulation software ProSimPlus v3.6.16. Detailed simulation models of the heat-exchanger-reactor, a mathematical model of the HT-PEM fuel cell, and other components are presented. The results obtained by the simulation model and by the experimental micro-cogenerator are compared and discussed. To fully understand the behavior of the integrated system and assess its flexibility, a parametric study is performed considering fuel partialization and important operating parameters. The values of the air-to-fuel ratio = [30, 7.5] and steam-to-carbon ratio = 3.5 (corresponding to net electrical and thermal efficiencies of 21.5 and 71.4%) are chosen for the analysis of inlet/outlet component temperatures. Finally, the exchange network analysis of the full process proves that the process efficiencies can still be increased by further improving the process internal heat integration.

A Comparative Study of CCM and CCS Membrane Electrode Assemblies for High-Temperature Proton Exchange Membrane Fuel Cells with a CsH5(PO4)2-Doped Polybenzimidazole Membrane.

Membrane electrode assemblies (MEAs) are critical components in influencing the electrochemical performance of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). MEA manufacturing processes are mainly divided into the catalyst-coated membrane (CCM) and the catalyst-coated substrate (CCS) methods. For conventional HT-PEMFCs based on phosphoric acid-doped polybenzimidazole (PBI) membranes, the wetting surface and extreme swelling of the PA-doped PBI membranes make the CCM method difficult to apply to the fabrication of MEAs. In this study, by taking advantage of the dry surface and low swelling of a CsH5(PO4)2-doped PBI membrane, an MEA fabricated by the CCM method was compared with an MEA made by the CCS method. Under each temperature condition, the peak power density of the CCM-MEA was higher than that of the CCS-MEA. Furthermore, under humidified gas conditions, an enhancement in the peak power densities was observed for both MEAs, which was attributed to the increase in the conductivity of the electrolyte membrane. The CCM-MEA exhibited a peak power density of 647 mW cm-2 at 200 °C, which was ~16% higher than that of the CCS-MEA. Electrochemical impedance spectroscopy results showed that the CCM-MEA had lower ohmic resistance, which implied that it had better contact between the membrane and catalyst layer.

Phosphonated Ionomers of Intrinsic Microporosity with Partially Ordered Structure for High-Temperature Proton Exchange Membrane Fuel Cells.

High mass transport resistance within the catalyst layer is one of the major factors restricting the performance and low Pt loadings of proton exchange membrane fuel cells (PEMFCs). To resolve the issue, a novel partially ordered phosphonated ionomer (PIM-P) with both an intrinsic microporous structure and proton-conductive functionality was designed as the catalyst binder to improve the mass transport of electrodes. The rigid and contorted structure of PIM-P limits the free movement of the conformation and the efficient packing of polymer chains, resulting in the formation of a robust gas transmission channel. The phosphonated groups provide sites for stable proton conduction. In particular, by incorporating fluorinated and phosphonated groups strategically on the local side chains, an orderly stacking of molecular chains based on group assembly contributes to the construction of efficient mass transport pathways. The peak power density of the membrane electrode assembly with the PIM-P ionomer is 18-379% greater than that of those with commercial or porous catalyst binders at 160 °C under an H2/O2 condition. This study emphasizes the crucial role of ordered structure in the rapid conduction of polymers with intrinsic microporosity and provides a new idea for increasing mass transport at electrodes from the perspective of structural design instead of complex processes.

Construction of Highly Conductive Cross-Linked Polybenzimidazole-Based Networks for High-Temperature Proton Exchange Membrane Fuel Cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) are of great interest to researchers in industry and academia because of their wide range of applications. This review lists some creative cross-linked polybenzimidazole-based membranes that have been prepared in recent years. Based on the investigation into their chemical structure, the properties of cross-linked polybenzimidazole-based membranes and the prospect of their future applications are discussed. The focus is on the construction of cross-linked structure of various types of polybenzimidazole-based membranes and their effect on proton conductivity. This review expresses the outlook and good expectation of the future direction of cross-linked polybenzimidazole membranes.

Thermodynamic Modeling and Exergy Analysis of A Combined High-Temperature Proton Exchange Membrane Fuel Cell and ORC System for Automotive Applications

A combined system consisting of a high-temperature proton exchange membrane fuel cell (HT-PEMFC) and an organic Rankine cycle (ORC) is provided for automotive applications in this paper. The combined system uses HT-PEMFC stack cathode exhaust gas to preheat the inlet gas and the ORC to recover the waste heat from the stack. The model of the combined system was developed and the feasibility of the model was verified. In addition, the evaluation index of the proposed system was derived through an energy and exergy analysis. The numerical simulation results show that the HT-PEMFC stack, cathode heat exchanger, and evaporator contributed the most to the total exergy loss of the system. These components should be optimized as a focus of future research to improve system performance. The lower current density increased the ecological function and the system efficiency, but reduced the system's net out-power. A higher inlet temperature and higher hydrogen pressures of the stack and the lower oxygen pressure helped improve the system performance. Compared to the HT-PEFC system without an ORC subsystem, the output power of the combined system was increased by 12.95%.

Thermodynamic and Physical Simulation of a High-Temperature Proton-Exchange Membrane Fuel Cell

Thermodynamic and Physical Simulation of a High-Temperature Proton-Exchange Membrane Fuel Cell

Performance Analysis Based on Sustainability Exergy Indicators of High-Temperature Proton Exchange Membrane Fuel Cell.

Based on finite-time thermodynamics, an irreversible high-temperature proton exchange membrane fuel cell (HT-PEMFC) model is developed, and the mathematical expressions of exergy efficiency, exergy destruction index (), and exergy sustainability indicators () of HT-PEMFC are derived. According to HT-PEMFC model, the influences of thermodynamic irreversibility on exergy sustainability of HT-PEMFC are researched under different operating parameters that include operating temperatures, inlet pressure, and current density. The results show that the higher operating temperature and inlet pressure of HT-PEMFCs is beneficial to performance improvement. In addition, the single cell performance gradually decreases with increasing current density due to the presence of the irreversibility of HT-PEMFC.

Literature Review of Energy Management in Combined Heat and Power Systems Based on High-Temperature Proton Exchange Membrane Fuel Cells for Residential Comfort Applications

Combined heat and power technologies represent an efficient way to ensure energy efficiency, as they promote usage of both electrical and thermal energy, something not done by most traditional energy sources, especially in residential environments. In this context, high-temperature proton exchange membrane fuel cells allow the implementation of combined heat and power systems. Additionally, in this environment, fuel cells are more efficient and less polluting than their traditional counterparts. We present a literature review of energy management in residential systems based on this type of fuel cell. In addition, we classify and detail the current state of fuel cell technologies, paying special attention to their characteristics, mathematical modelling and control, as well as combined heat and power systems and energy management strategies.

Numerical Study of the Flow Field Distributor in High-temperature Proton-exchange Membrane Fuel Cells

Numerical Study of the Flow Field Distributor in High-temperature Proton-exchange Membrane Fuel Cells

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.

Voltage Readjustment Methodology According to Pressure and Temperature Applied to a High Temperature PEM Fuel Cell

The operating conditions can have uncontrolled effects on the voltage of a High-Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC). For instance, the HT-PEMFC can be used at ambient pressure, i.e., without having a back pressure regulator. In this case, the variation in the atmospheric pressure directly affects pressures inside the fuel cell, which induces voltage variation. Moreover, in transient phases, several coupled phenomena can have an uncontrolled effect on the voltage. For example, following a change in the current operating point, thermal conditions in the fuel cell can vary, and the temperature stabilization then leads to a voltage variation. This article introduces a readjustment method for the fuel cell voltage to compensate for the effects of the pressure and temperature variations that are undergone and to decouple their effects. This methodology is based on the realization of a design of experiments to characterize the voltage sensitivity to pressure ([1; 1.5 bar]) and temperature ([120; 180 °C]) between 0.2 and 1 A/cm2 of an Advent PBI MEA (formerly BASF Celtec®-P 1100 W). The data obtained allowed identifying an empirical model that takes into account the aging caused by the experiment. Finally, the methodology is criticized before proposing an alternative method.

Simulating the effects of flow configurations on auxiliary power requirement and net power output of High-Temperature Proton Exchange Membrane Fuel Cell

High-temperature proton exchange membrane fuel cells have garnered huge attention in the recent past because of faster electrode kinetics, high CO tolerance, and possible waste heat recovery. The flow channel is a crucial component of the fuel cell, which helps to improve its performance by facilitating uniform distribution of the reactant species, current density, and temperature. Conversely, the pressure drop imposed by various flow channel configurations increases the auxiliary power requirement of the fuel cell, which is a critical issue. Here, the main objectives are to enhance the electrochemical performance and reduce the auxiliary power loss of the high-temperature proton exchange membrane fuel cell by selecting a proper flow configuration. This work compares the parallel, serpentine, and hybrid flow configurations using a physics-based fuel cell model. It involves the mass, momentum, energy, species, and current conservation equations. The simulation results show that the shape and size of the common channel width in the parallel flow configuration have a noticeable influence on the cell performance. The thermal analysis demonstrates that the temperature gradients of the serpentine and hybrid configurations are two times lower than the parallel configuration due to uniform current density distribution and heat dissipation. This study illustrates that the hybrid configuration with the net power output of 0.383 W/cm2 provides the best performance with an auxiliary power loss of 3.6% compared to the serpentine configuration with an 11% loss. The net power output of the hybrid configuration remains superior under various stoichiometric conditions, including cell starvation. The outcome of this work provides a helpful insight into the flow configuration design for maximizing the net available power from the cell.