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Special Issue "Fuel Cells"

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A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (31 December 2009)

Special Issue Information

Summary

Fuel cells allow the direct conversion of chemically stored energy into electrical energy by means of electrochemical oxidation of gaseous, liquid or solid chemical substances. Depending on the type of electrolyte being used, we distinguish between Alkaline Fuel Cells (AFC), Phoshoric Acid Fuel Cells (PAFC), Proton Exchange Membrane Fuel Cells (PEMFC), Molten Carbonate Fuel Cells (MCFC) and Solid Oxide Fuel Cells (SOFC). The preferred fuel for fuel cells is hydrogen. But since this is not a natural resource, hydrogen has to be produced either externally or internally, i.e. outside or inside the fuel cells. The latter case leads to the very attractive concept of direct fuel cells, which are able to convert hydrocarbons into hydrogen, e.g. via internal reforming. The special issue covers current trends and future developments of fuel cell technology, including both chemical as well as electrical engineering aspects.

Keywords

  • AFC
  • PAFC
  • PEMFC
  • MCFC
  • SOFC
  • hydrogen
  • electrochemical energy conversion

Published Papers (19 papers)

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Research

Jump to: Review

Open AccessArticle A Transient Model for Fuel Cell Cathode-Water Propagation Behavior inside a Cathode after a Step Potential
Energies 2010, 3(5), 920-939; doi:10.3390/en3050920
Received: 9 March 2010 / Revised: 21 April 2010 / Accepted: 26 April 2010 / Published: 30 April 2010
Cited by 2 | PDF Full-text (421 KB) | HTML Full-text | XML Full-text
Abstract
Most of the voltage losses of proton exchange membrane fuel cells (PEMFC) are due to the sluggish kinetics of oxygen reduction on the cathode and the low oxygen diffusion rate inside the flooded cathode. To simulate the transient flooding in the cathode [...] Read more.
Most of the voltage losses of proton exchange membrane fuel cells (PEMFC) are due to the sluggish kinetics of oxygen reduction on the cathode and the low oxygen diffusion rate inside the flooded cathode. To simulate the transient flooding in the cathode of a PEMFC, a transient model was developed. This model includes the material conservation of oxygen, vapor, water inside the gas diffusion layer (GDL) and micro-porous layer (MPL), and the electrode kinetics in the cathode catalyst layer (CL). The variation of hydrophobicity of each layer generated a wicking effect that moves water from one layer to the other. Since the GDL, MPL, and CL are made of composite materials with different hydrophilic and hydrophobic properties, a linear function of saturation was used to calculate the wetting contact angle of these composite materials. The balance among capillary force, gas/liquid pressure, and velocity of water in each layer was considered. Therefore, the dynamic behavior of PEMFC, with saturation transportation taken into account, was obtained in this study. A step change of the cell voltage was used to illustrate the transient phenomena of output current, water movement, and diffusion of oxygen and water vapor across the entire cathode. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessArticle Integration of A Solid Oxide Fuel Cell into A 10 MW Gas Turbine Power Plant
Energies 2010, 3(4), 754-769; doi:10.3390/en3040754
Received: 4 February 2010 / Accepted: 9 March 2010 / Published: 14 April 2010
Cited by 12 | PDF Full-text (381 KB) | HTML Full-text | XML Full-text
Abstract
Power generation using gas turbine power plants operating on the Brayton cycle suffers from low efficiencies. In this work, a solid oxide fuel cell (SOFC) is proposed for integration into a 10 MW gas turbine power plant, operating at 30% efficiency. The [...] Read more.
Power generation using gas turbine power plants operating on the Brayton cycle suffers from low efficiencies. In this work, a solid oxide fuel cell (SOFC) is proposed for integration into a 10 MW gas turbine power plant, operating at 30% efficiency. The SOFC system utilizes four heat exchangers for heat recovery from both the turbine outlet and the fuel cell outlet to ensure a sufficiently high SOFC temperature. The power output of the hybrid plant is 37 MW at 66.2% efficiency. A thermo-economic model predicts a payback period of less than four years, based on future projected SOFC cost estimates. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessArticle Current Density Distribution Mapping in PEM Fuel Cells as An Instrument for Operational Measurements
Energies 2010, 3(4), 770-783; doi:10.3390/en3040770
Received: 3 February 2010 / Accepted: 23 February 2010 / Published: 14 April 2010
Cited by 7 | PDF Full-text (670 KB) | HTML Full-text | XML Full-text
Abstract
A newly developed measurement system for current density distribution mapping has enabled a new approach for operational measurements in proton exchange membrane fuel cells (PEMFC). Taking into account previously constructed measurement systems, a method based on a multi layer printed circuit board [...] Read more.
A newly developed measurement system for current density distribution mapping has enabled a new approach for operational measurements in proton exchange membrane fuel cells (PEMFC). Taking into account previously constructed measurement systems, a method based on a multi layer printed circuit board was chosen for the development of the new system. This type of system consists of a sensor, a special electronic device and the control and visualization PC. For the acquisition of the current density distribution values, a sensor device was designed and installed within a multilayer printed circuit board with integrated shunt resistors. Varying shunt values can be taken into consideration with a newly developed and evaluated calibration method. The sensor device was integrated in a PEM fuel cell stack to prove the functionality of the whole measurement system. A software application was implemented to visualize and save the measurement values. Its functionality was verified by operational measurements within a PEMFC system. Measurement accuracy and possible negative reactions of the sensor device during PEMFC operation are discussed in detail in this paper. The developed system enables operational measurements for different operating phases of PEM fuel cells. Additionally, this can be seen as a basis for new opportunities of optimization for fuel cell design and operation modes. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessArticle Assessment of the Effects of Flow Rate and Ionic Strength on the Performance of an Air-Cathode Microbial Fuel Cell Using Electrochemical Impedance Spectroscopy
Energies 2010, 3(4), 592-606; doi:10.3390/en3040592
Received: 5 January 2010 / Revised: 27 February 2010 / Accepted: 15 March 2010 / Published: 26 March 2010
Cited by 17 | PDF Full-text (245 KB) | HTML Full-text | XML Full-text
Abstract
Impedance changes of the anode, cathode and solution were examined for an air-cathode microbial fuel cell (MFC) under varying conditions. An MFC inoculated with a pre-enriched microbial culture resulted in a startup time of less than ten days. Over this period, the [...] Read more.
Impedance changes of the anode, cathode and solution were examined for an air-cathode microbial fuel cell (MFC) under varying conditions. An MFC inoculated with a pre-enriched microbial culture resulted in a startup time of less than ten days. Over this period, the anode impedance decreased below the cathode impedance, suggesting a cathode-limited power output. Increasing the anode flow rate did not impact the anode impedance significantly, but it decreased the cathode impedance by 65%. Increasing the anode-medium ionic strength also decreased the cathode impedance. These impedance results provide insight into electron and proton transport mechanisms and can be used to improve MFC performance. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessArticle Synthesis and Evaluation of Highly Tolerant Pd Electrocatalysts as Cathodes in Direct Ethylene Glycol Fuel Cells (DEGFC)
Energies 2009, 2(4), 944-956; doi:10.3390/en20400944
Received: 29 July 2009 / Accepted: 11 September 2009 / Published: 27 October 2009
Cited by 6 | PDF Full-text (678 KB) | HTML Full-text | XML Full-text
Abstract
Highly selective Pd electrocatalysts were synthesized by the formic acid (FA) method and evaluated as cathodes for DEGFC applications. In rotating disc measurements in acid medium, the Pd/C cathode showed important catalytic activity for the Oxygen Reduction Reaction (ORR). In the presence [...] Read more.
Highly selective Pd electrocatalysts were synthesized by the formic acid (FA) method and evaluated as cathodes for DEGFC applications. In rotating disc measurements in acid medium, the Pd/C cathode showed important catalytic activity for the Oxygen Reduction Reaction (ORR). In the presence of ethylene glycol (EG, C2H6O2), Pd/C exhibited a noteworthy electrochemical behavior and full tolerance to the organic molecule. No current density peaks associated to the EG oxidation reaction emerged and the shift in onset potential for the ORR (Eonset) toward more negative potentials was negligible on this cathode. As a comparison, commercial Pt/C was tested under the same conditions showing a poor selectivity for the ORR when EG was present. The detrimental effect of EG on the Pt electrocatalysts resulted in high intensity current density peaks due to the oxidation of EG and a significant shift in Eonset. The evaluation of Pd/C in a DEGFC operating at 80 °C demonstrated its good performance as cathode material. Given these results, it is expected that highly efficient Pd-based cathodes can find application in DEGFCs. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessArticle Methanol Electro-Oxidation on Pt-Ru Alloy Nanoparticles Supported on Carbon Nanotubes
Energies 2009, 2(3), 789-804; doi:10.3390/en20300789
Received: 5 August 2009 / Accepted: 11 September 2009 / Published: 16 September 2009
Cited by 19 | PDF Full-text (209 KB) | HTML Full-text | XML Full-text
Abstract
Carbon nanotubes (CNTs) have been investigated in recent years as a catalyst support for proton exchange membrane fuel cells. Improved catalyst activities were observed and attributed to metal-support interactions. We report a study on the kinetics of methanol electro-oxidation on CNT supported [...] Read more.
Carbon nanotubes (CNTs) have been investigated in recent years as a catalyst support for proton exchange membrane fuel cells. Improved catalyst activities were observed and attributed to metal-support interactions. We report a study on the kinetics of methanol electro-oxidation on CNT supported Pt-Ru alloy nanoparticles. Alloy catalysts with different compositions, Pt53Ru47/CNT, Pt69Ru31/CNT and Pt77Ru23/CNT, were prepared and investigated in detail. Experiments were conducted at various temperatures, electrode potentials, and methanol concentrations. It was found that the reaction order of methanol electro-oxidation on the PtRu/CNT catalysts was consistent with what has been reported for PtRu alloys with a value of 0.5 in methanol concentrations. However, the electro-oxidation reaction on the PtRu/CNT catalysts displayed much lower activation energies than that on the Pt-Ru alloy catalysts unsupported or supported on carbon black (PtRu/CB). This study provides an overall kinetic evaluation of the PtRu/CNT catalysts and further demonstrates the beneficial role of CNTs. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessArticle A Simulation Tool for Geometrical Analysis and Optimization of Fuel Cell Bipolar Plates: Development, Validation and Results
Energies 2009, 2(3), 582-594; doi:10.3390/en20300582
Received: 1 July 2009 / Revised: 16 July 2009 / Accepted: 29 July 2009 / Published: 31 July 2009
Cited by 4 | PDF Full-text (696 KB)
Abstract
Bipolar plates (BPs) are one of the most important components in Proton Exchange Membrane Fuel Cells (PEMFC) due to the numerous functions they perform. The objective of the research work described in this paper was to develop a simplified and validated method [...] Read more.
Bipolar plates (BPs) are one of the most important components in Proton Exchange Membrane Fuel Cells (PEMFC) due to the numerous functions they perform. The objective of the research work described in this paper was to develop a simplified and validated method based on Computational Fluid Dynamics (CFD), aimed at the analysis and study of the influence of geometrical parameters of BPs on the operation of a cell. A complete sensibility analysis of the influence of dimensions and shape of the BP can be obtained through a simplified CFD model without including the complexity of other components of the PEMFC. This model is compared with the PEM Fuel Cell Module of the FLUENT software, which includes the physical and chemical phenomena relevant in PEMFCs. Results with both models regarding the flow field inside the channels and local current densities are obtained and compared. The results show that it is possible to use the simple model as a standard tool for geometrical analysis of BPs, and results of a sensitivity analysis using the simplified model are presented and discussed. Full article
(This article belongs to the Special Issue Fuel Cells)
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Open AccessArticle A Microscale Modeling Tool for the Design and Optimization of Solid Oxide Fuel Cells
Energies 2009, 2(2), 427-444; doi:10.3390/en20200427
Received: 22 May 2009 / Revised: 9 June 2009 / Accepted: 10 June 2009 / Published: 23 June 2009
Cited by 13 | PDF Full-text (650 KB) | HTML Full-text | XML Full-text
Abstract
A two dimensional numerical model of a solid oxide fuel cell (SOFC) with electrode functional layers is presented. The model incorporates the partial differential equations for mass transport, electric conduction and electrochemical reactions in the electrode functional layers, the anode support layer, [...] Read more.
A two dimensional numerical model of a solid oxide fuel cell (SOFC) with electrode functional layers is presented. The model incorporates the partial differential equations for mass transport, electric conduction and electrochemical reactions in the electrode functional layers, the anode support layer, the cathode current collection layer and at the electrode/electrolyte interfaces. A dusty gas model is used in modeling the gas transport in porous electrodes. The model is capable of providing results in good agreement with the experimental I-V relationship. Numerical examples are presented to illustrate the applications of this numerical model as a tool for the design and optimization of SOFCs. For a stack assembly of a pitch width of 2 mm and an interconnect-electrode contact resistance of 0.025 Ωcm2, a typical SOFC stack cell should consist of a rib width of 0.9 mm, a cathode current collection layer thickness of 200–300 μm, a cathode functional layer thickness of 20–40 μm, and an anode functional layer thickness of 10–20 μm in order to achieve optimal performance. Full article
(This article belongs to the Special Issue Fuel Cells)
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Open AccessArticle A Self-Supported Direct Borohydride-Hydrogen Peroxide Fuel Cell System
Energies 2009, 2(2), 190-201; doi:10.3390/en20200190
Received: 20 March 2009 / Revised: 2 April 2009 / Accepted: 8 April 2009 / Published: 14 April 2009
Cited by 8 | PDF Full-text (418 KB) | HTML Full-text | XML Full-text
Abstract
A self-supported direct borohydride-hydrogen peroxide fuel cell system with internal manifolds and an auxiliary control unit is reported. The system, while operating under ambient conditions, delivers a peak power of 40 W with about 2 W to run the auxiliary control unit. [...] Read more.
A self-supported direct borohydride-hydrogen peroxide fuel cell system with internal manifolds and an auxiliary control unit is reported. The system, while operating under ambient conditions, delivers a peak power of 40 W with about 2 W to run the auxiliary control unit. A critical cause and effect analysis, on the data for single cells and stack, suggests the optimum concentrations of fuel and oxidant to be 8 wt. % NaBH4 and 2 M H2O2, respectively in extending the operating time of the system. Such a fuel cell system is ideally suited for submersible and aerospace applications where anaerobic conditions prevail. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessArticle Analysis of the Coupling Behavior of PEM Fuel Cells and DC-DC Converters
Energies 2009, 2(1), 71-96; doi:10.3390/en2010071
Received: 8 January 2009 / Accepted: 19 February 2009 / Published: 4 March 2009
Cited by 3 | PDF Full-text (1543 KB) | HTML Full-text | XML Full-text
Abstract
The connection between PEM fuel cells and common DC-DC converters is examined. The analysis is model-based and done for boost, buck and buck-boost converters. In a first step, the effect of the converter ripples upon the PEM fuel cell is shown. They [...] Read more.
The connection between PEM fuel cells and common DC-DC converters is examined. The analysis is model-based and done for boost, buck and buck-boost converters. In a first step, the effect of the converter ripples upon the PEM fuel cell is shown. They introduce oscillations in the fuel cell. Their appearance is explained, discussed and possibilities for their suppression are given. After that, the overall behaviors of the coupled fuel cell-converter systems are analyzed. It is shown, that neither stationary multiplicities nor oscillations can be introduced by the couplings and therefore separate control approaches for both the PEMFC and the DC-DC converters are applicable. Full article
(This article belongs to the Special Issue Fuel Cells)
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Review

Jump to: Research

Open AccessReview Principles and Materials Aspects of Direct Alkaline Alcohol Fuel Cells
Energies 2010, 3(8), 1499-1528; doi:10.3390/en3081499
Received: 21 July 2010 / Revised: 6 August 2010 / Accepted: 16 August 2010 / Published: 24 August 2010
Cited by 116 | PDF Full-text (424 KB) | HTML Full-text | XML Full-text
Abstract
Direct alkaline alcohol fuel cells (DAAFCs) have attracted increasing interest over the past decade because of their favourable reaction kinetics in alkaline media, higher energy densities achievable and the easy handling of the liquid fuels. In this review, principles and mechanisms of [...] Read more.
Direct alkaline alcohol fuel cells (DAAFCs) have attracted increasing interest over the past decade because of their favourable reaction kinetics in alkaline media, higher energy densities achievable and the easy handling of the liquid fuels. In this review, principles and mechanisms of DAAFCs in alcohol oxidation and oxygen reduction are discussed. Despite the high energy densities available during the oxidation of polycarbon alcohols they are difficult to oxidise. Apart from methanol, the complete oxidation of other polycarbon alcohols to CO2 has not been achieved with current catalysts. Different types of catalysts, from conventional precious metal catalyst of Pt and Pt alloys to other lower cost Pd, Au and Ag metal catalysts are compared. Non precious metal catalysts, and lanthanum, strontium oxides and perovskite-type oxides are also discussed. Membranes like the ones used as polymer electrolytes and developed for DAAFCs are reviewed. Unlike conventional proton exchange membrane fuel cells, anion exchange membranes are used in present DAAFCs. Fuel cell performance with DAAFCs using different alcohols, catalysts and membranes, as well as operating parameters are summarised. In order to improve the power output of the DAAFCs, further developments in catalysts, membrane materials and fuel cell systems are essential. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessReview Microbial Fuel Cells, A Current Review
Energies 2010, 3(5), 899-919; doi:10.3390/en3050899
Received: 19 January 2010 / Revised: 13 March 2010 / Accepted: 24 March 2010 / Published: 28 April 2010
Cited by 130 | PDF Full-text (507 KB) | HTML Full-text | XML Full-text
Abstract
Microbial fuel cells (MFCs) are devices that can use bacterial metabolism to produce an electrical current from a wide range organic substrates. Due to the promise of sustainable energy production from organic wastes, research has intensified in this field in the last [...] Read more.
Microbial fuel cells (MFCs) are devices that can use bacterial metabolism to produce an electrical current from a wide range organic substrates. Due to the promise of sustainable energy production from organic wastes, research has intensified in this field in the last few years. While holding great promise only a few marine sediment MFCs have been used practically, providing current for low power devices. To further improve MFC technology an understanding of the limitations and microbiology of these systems is required. Some researchers are uncovering that the greatest value of MFC technology may not be the production of electricity but the ability of electrode associated microbes to degrade wastes and toxic chemicals. We conclude that for further development of MFC applications, a greater focus on understanding the microbial processes in MFC systems is required. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessReview Recent Advances in Enzymatic Fuel Cells: Experiments and Modeling
Energies 2010, 3(4), 803-846; doi:10.3390/en3040803
Received: 4 January 2010 / Revised: 23 February 2010 / Accepted: 3 March 2010 / Published: 21 April 2010
Cited by 79 | PDF Full-text (1572 KB) | HTML Full-text | XML Full-text
Abstract
Enzymatic fuel cells convert the chemical energy of biofuels into electrical energy. Unlike traditional fuel cell types, which are mainly based on metal catalysts, the enzymatic fuel cells employ enzymes as catalysts. This fuel cell type can be used as an implantable [...] Read more.
Enzymatic fuel cells convert the chemical energy of biofuels into electrical energy. Unlike traditional fuel cell types, which are mainly based on metal catalysts, the enzymatic fuel cells employ enzymes as catalysts. This fuel cell type can be used as an implantable power source for a variety of medical devices used in modern medicine to administer drugs, treat ailments and monitor bodily functions. Some advantages in comparison to conventional fuel cells include a simple fuel cell design and lower cost of the main fuel cell components, however they suffer from severe kinetic limitations mainly due to inefficiency in electron transfer between the enzyme and the electrode surface. In this review article, the major research activities concerned with the enzymatic fuel cells (anode and cathode development, system design, modeling) by highlighting the current problems (low cell voltage, low current density, stability) will be presented. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessReview Single-Chamber Solid Oxide Fuel Cell Technology—From Its Origins to Today’s State of the Art
Energies 2010, 3(1), 57-134; doi:10.3390/en3010057
Received: 3 November 2009 / Accepted: 31 December 2009 / Published: 15 January 2010
Cited by 42 | PDF Full-text (977 KB) | HTML Full-text | XML Full-text
Abstract
In single-chamber solid oxide fuel cells (SC-SOFCs), both anode and cathode are situated in a common gas chamber and are exposed to a mixture of fuel and oxidant. The working principle is based on the difference in catalytic activity of the electrodes [...] Read more.
In single-chamber solid oxide fuel cells (SC-SOFCs), both anode and cathode are situated in a common gas chamber and are exposed to a mixture of fuel and oxidant. The working principle is based on the difference in catalytic activity of the electrodes for the respective anodic and cathodic reactions. The resulting difference in oxygen partial pressure between the electrodes leads to the generation of an open circuit voltage. Progress in SC-SOFC technology has enabled the generation of power outputs comparable to those of conventional SOFCs. This paper provides a detailed review of the development of SC-SOFC technology. Full article
(This article belongs to the Special Issue Fuel Cells)
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Open AccessReview Enzymatic Biofuel Cells—Fabrication of Enzyme Electrodes
Energies 2010, 3(1), 23-42; doi:10.3390/en3010023
Received: 9 November 2009 / Accepted: 4 January 2010 / Published: 11 January 2010
Cited by 50 | PDF Full-text (833 KB) | HTML Full-text | XML Full-text
Abstract
Enzyme based bioelectronics have attracted increasing interest in recent years because of their applications on biomedical research and healthcare. They also have broad applications in environmental monitoring, and as the power source for portable electronic devices. In this review, the technology developed [...] Read more.
Enzyme based bioelectronics have attracted increasing interest in recent years because of their applications on biomedical research and healthcare. They also have broad applications in environmental monitoring, and as the power source for portable electronic devices. In this review, the technology developed for fabrication of enzyme electrodes has been described. Different enzyme immobilisation methods using layered structures with self-assembled monolayers (SAM) and entrapment of enzymes in polymer matrixes have been reviewed. The performances of enzymatic biofuel cells are summarised. Various approaches on further development to overcome the current challenges have been discussed. This innovative technology will have a major impact and benefit medical science and clinical research, healthcare management, energy production from renewable sources. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessReview Strategies for Lowering Solid Oxide Fuel Cells Operating Temperature
Energies 2009, 2(4), 1130-1150; doi:10.3390/en20401130
Received: 27 October 2009 / Accepted: 13 November 2009 / Published: 25 November 2009
Cited by 31 | PDF Full-text (794 KB) | HTML Full-text | XML Full-text
Abstract
Lowering the operating temperature of solid oxide fuel cells (SOFCs) to the intermediate range (500–700 ºC) has become one of the main SOFC research goals. High operating temperatures put numerous requirements on materials selection and on secondary units, limiting the commercial development [...] Read more.
Lowering the operating temperature of solid oxide fuel cells (SOFCs) to the intermediate range (500–700 ºC) has become one of the main SOFC research goals. High operating temperatures put numerous requirements on materials selection and on secondary units, limiting the commercial development of SOFCs. The present review first focuses on the main effects of reducing the operating temperature in terms of materials stability, thermo-mechanical mismatch, thermal management and efficiency. After a brief survey of the state-of-the-art materials for SOFCs, attention is focused on emerging oxide-ionic conductors with high conductivity in the intermediate range of temperatures with an introductory section on materials technology for reducing the electrolyte thickness. Finally, recent advances in cathode materials based on layered mixed ionic-electronic conductors are highlighted because the decreasing temperature converts the cathode into the major source of electrical losses for the whole SOFC system. It is concluded that the introduction of alternative materials that would enable solid oxide fuel cells to operate in the intermediate range of temperatures would have a major impact on the commercialization of fuel cell technology. Full article
(This article belongs to the Special Issue Fuel Cells)
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Open AccessReview A Review of Water Management in Polymer Electrolyte Membrane Fuel Cells
Energies 2009, 2(4), 1057-1106; doi:10.3390/en20401057
Received: 4 September 2009 / Accepted: 11 November 2009 / Published: 17 November 2009
Cited by 74 | PDF Full-text (1362 KB) | HTML Full-text | XML Full-text
Abstract
At present, despite the great advances in polymer electrolyte membrane fuel cell (PEMFC) technology over the past two decades through intensive research and development activities, their large-scale commercialization is still hampered by their higher materials cost and lower reliability and durability. In [...] Read more.
At present, despite the great advances in polymer electrolyte membrane fuel cell (PEMFC) technology over the past two decades through intensive research and development activities, their large-scale commercialization is still hampered by their higher materials cost and lower reliability and durability. In this review, water management is given special consideration. Water management is of vital importance to achieve maximum performance and durability from PEMFCs. On the one hand, to maintain good proton conductivity, the relative humidity of inlet gases is typically held at a large value to ensure that the membrane remains fully hydrated. On the other hand, the pores of the catalyst layer (CL) and the gas diffusion layer (GDL) are frequently flooded by excessive liquid water, resulting in a higher mass transport resistance. Thus, a subtle equilibrium has to be maintained between membrane drying and liquid water flooding to prevent fuel cell degradation and guarantee a high performance level, which is the essential problem of water management. This paper presents a comprehensive review of the state-of-the-art studies of water management, including the experimental methods and modeling and simulation for the characterization of water management and the water management strategies. As one important aspect of water management, water flooding has been extensively studied during the last two decades. Herein, the causes, detection, effects on cell performance and mitigation strategies of water flooding are overviewed in detail. In the end of the paper the emphasis is given to: (i) the delicate equilibrium of membrane drying vs. water flooding in water management; (ii) determining which phenomenon is principally responsible for the deterioration of the PEMFC performance, the flooding of the porous electrode or the gas channels in the bipolar plate, and (iii) what measures should be taken to prevent water flooding from happening in PEMFCs. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessReview Transition Metal Carbides and Nitrides as Electrode Materials for Low Temperature Fuel Cells
Energies 2009, 2(4), 873-899; doi:10.3390/en20400873
Received: 28 August 2009 / Accepted: 25 September 2009 / Published: 13 October 2009
Cited by 115 | PDF Full-text (2042 KB) | HTML Full-text | XML Full-text
Abstract
Transition metal carbides (TMCs) and transition metal nitrides (TMNs) have attracted attention as promising electrocatalysts that could replace noble metals of high price and limited supply. Relative to parent metals, TMC and TMN behave like noble metals for electrochemical reactions such as [...] Read more.
Transition metal carbides (TMCs) and transition metal nitrides (TMNs) have attracted attention as promising electrocatalysts that could replace noble metals of high price and limited supply. Relative to parent metals, TMC and TMN behave like noble metals for electrochemical reactions such as oxidation of hydrogen, CO and alcohols, and reduction of oxygen. When TMC and TMN are combined with other metals, the electrocatalytic synergy is often observed in electrochemical reactions. Thus, combinations with a minute amount of Pt or even non-Pt metals give performance comparable to heavily loaded Pt-based electrocatalysts for low temperature fuel cells. It appears that TMC based electrocatalysts are more active as anode catalysts for oxidation of fuels, whereas TMN based catalysts are more active for cathode catalysts for oxygen reduction and more stable. Full article
(This article belongs to the Special Issue Fuel Cells)
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Open AccessReview Direct Utilization of Liquid Fuels in SOFC for Portable Applications: Challenges for the Selection of Alternative Anodes
Energies 2009, 2(2), 377-410; doi:10.3390/en20200377
Received: 11 May 2009 / Revised: 30 May 2009 / Accepted: 2 June 2009 / Published: 12 June 2009
Cited by 51 | PDF Full-text (1439 KB) | HTML Full-text | XML Full-text
Abstract
Solid oxide fuel cells (SOFC) have the advantage of being able to operate with fuels other than hydrogen. In particular, liquid fuels are especially attractive for powering portable applications such as small power generators or auxiliary power units, in which case the [...] Read more.
Solid oxide fuel cells (SOFC) have the advantage of being able to operate with fuels other than hydrogen. In particular, liquid fuels are especially attractive for powering portable applications such as small power generators or auxiliary power units, in which case the direct utilization of the fuel would be convenient. Although liquid fuels are easier to handle and transport than hydrogen, their direct use in SOFC can lead to anode deactivation due to carbon formation, especially on traditional nickel/yttria stabilized zirconia (Ni/YSZ) anodes. Significant advances have been made in anodic materials that are resistant to carbon formation but often these materials are less electrochemically active than Ni/YSZ. In this review the challenges of using liquid fuels directly in SOFC, in terms of gas-phase and catalytic reactions within the anode chamber, will be discussed and the alternative anode materials so far investigated will be compared. Full article
(This article belongs to the Special Issue Fuel Cells)

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