High Temperature Polymer Electrolyte Membrane Fuel Cells for Integrated Fuel Cell – Methanol Reformer Power Systems: A Critical Review

Abstract

be generally divided into low temperature fuel cells such as alkaline fuel cells (AFCs), polymer electrolyte membrane fuel cells (PEMFCs) and phosphoric acid fuel cells (PAFCs) and high temperature fuel cells such as molten carbonate fuel cells (MCFCs) and solid oxide fuel cells (SOFCs). Due to their high power-output, fast start-up/shut-down cycles and continuous power supply mode, PEMFCs are particularly applicable as energy sources in portable electronic devices, communication and transportation applications. [1] The core component of PEMFCs is the membrane-electrode-assembly (MEA), which consists of a proton conducting polymer electrolyte membrane (PEM) sandwiched between anode and cathode catalyst layer. In the case of hydrogen fuel, H 2 is oxidized at the anode and protons are transported through the PEM to the cathode. At the cathode, protons are combined with electrons flew through external circuit, reducing ambient oxygen to water. The operation principle of a PEMFC is illustrated in Figure 1. Perfluorosulfonic acid (PFSA) membranes such as Nafion are the most common and successful PEMs for low temperature PEMFCs (i.e., operation at 80 °C or below) and possess a high acidity, high conductivity (e.g., for Nafion 117, conductivity can be as high as ∼0.1 S cm -1 at 30 °C and 100% relative humidity [2] ), and high chemical and structural stability. [3] However, Nafion membrane must be fully hydrated in order to have the high proton conductivity and the stable operation of Nafion membrane based fuel cells because its proton conductivity decreases rapidly with the decrease in relative humidity (RH). [4] Thereby, the operation temperatures are limited to 80 °C or below under ambient pressure in order to maintain a high water content in the membrane. As proton transport requires an aqueous medium or water to maintain the high conductivity, water management is critical for the stable operation of Nafion based PEMFCs. In the case of transportation applications, water-based PEMFC stacks also require adequate heat management, e.g., large radiators/heat exchangers to extract the heat. Another critical issue for PFSA membrane based PEMFCs is the requirement of high purity H 2 as the Pt based electrocatalysts shows a very low resistance to the fuel The development of reliable power sources is important for the continuous operation of various electric equipment in unmanned aircraft and the field environment. Currently electric power delivery to such systems is mainly by battery packs. An alternative is to use fuel cells (FCs). FCs are electrochemical devices that are used to convert chemical energy of fuels such as hydrogen and methanol to electricity. Methanol is an attractive fuel because it is liquid at ambient temperature, has a much higher energy density than hydrogen and low reforming temperature (220-300 °C). Thus, integration of methanol steam reformers (MSRs) with FCs makes it possible to continuously produce electricity. The key challenge in such power system is the development of fuel cells which can be effe...

Iron Single Atoms on Graphene as Nonprecious Metal Catalysts for High‐Temperature Polymer Electrolyte Membrane Fuel Cells

“…Generally, the increase of the operational temperature will increase the kinetics of reactions on the electrodes of fuel cells . On the other hand, an increase in the operational temperature would also decrease the conductivity of SiO 2 /PA/PBI‐based high temperature membranes as shown recently .…”

Advancement toward Polymer Electrolyte Membrane Fuel Cells at Elevated Temperatures

“…Compared with PBI, PVPbased composite membranes have an unparalleled cost advantage due to the wide availability and cheap and easy processing capabilities. A fundamental breakthrough in the membrane and proton carrier system with operating temperatures higher than 200°C will undoubtedly open new opportunities in the development of nonprecious metal (NPM) catalysts [113] and highly efficient and integrated MSR-PEMFC power systems [26] for practical and wide employment of fuel cell technologies in transportation, communication, and portable devices. The development of NPM catalysts will substantially reduce the cost of PEMFCs and is of great significance to the practical application and commercial viability of PEMFCs technology.…”

“…This review is devoted to a summary of the state-of-theart acid-doped PBI and solid inorganic proton conductors. The main focus is placed on updating of the advancement of inorganic/organic composite membranes and proton carriers particularly for operation at elevated temperatures, e.g., 200°C or higher, in order to enable a novel integrated power systems, as outlined recently [26]. Prospect and future direction in the development of new proton carrier systems at elevated temperatures are discussed.…”

An overview of the methanol reforming process: Comparison of fuels, catalysts, reformers, and systems

“…The configuration of an internal reforming methanol fuel cell system can be seen in Figure . Recent advancement in research related to integrated methanol steam reformer HT‐PEMFC power generation systems was reviewed in Zhang et al…”

“…They focused on recent improvements in catalysts for the partial oxidation of methane and alcohols. In addition, Zang et al recently reviewed the latest progress and achievements in integrated methanol steam reformer high‐temperature polymer electrolyte membrane fuel cell (HT‐PEMFC) power generation systems.…”