Polymer Electrolyte Membrane Fuel Cell (PEMFC) Flow Field Plate: Design, Materials and Characterisation

Abstract

Worldwide, there are growing pressures to develop 'carbonfree' societies, where the majority of the energy is produced from renewable technologies, due to climate change [1], adverse health effects [2], fuel resource depletion [3], security of energy supply, economics [4] and increasing tight international legislations [5]. In response to the above issues, many have proposed hydrogen for use as a replacement energy carrier in future energy economies as it produces no greenhouse gases, GHGs (e.g. CO 2 ) when burned or used in a fuel cell with only electricity, heat and water being formed. A fuel cell is an 'electrochemical' device operating at various temperatures (up to 1,000°C) that continuously and efficiently convert chemical energy (from fuel and oxidant) into electrical energy. There are various types of fuel cell including alkaline (AFC), phosphoric acid (PAFC), molten carbonate (MCFC), solid oxide (SOFC) and polymer electrolyte membrane fuel cell (PEMFC) also known as the proton exchange membrane fuel cell (PEMFC) with an efficiency of up to 60% and operating up to 180°C. There are two types of PEMFC: one uses hydrogen as a fuel and the other, methanol -direct methanol fuel cell (DMFC). They both use membrane electrode assemblies (MEAs) which is the heart of the PEM fuel cell where the electrochemical reactions occur. The MEA is a multilayered membrane consisting of a polymeric membrane sandwiched between catalyst layers and gas diffusion layers (GDLs). Currently, the most promising applications for PEM fuel cell are in the automotive sector with trials of buses, cars and motorcycles becoming increasingly common. Others applications include portable, stationary or backup power units. However, the cost, performance and durability still need to be improved if PEMFC is to become a viable alternative energy technology. For example, as 'a rule of thumb', flow field plates (FFPs) constitute 10% (7.7% for a 5 kWnet stack) of the total cost and more than 60% of the weight in PEM fuel cell stacks. For this reason, the weight, volume and cost of the fuel cell stack can be reduced significantly by improving the layout configuration of FFP and use of lightweight materials. Different combinations of materials, flowfield designs and fabrication techniques have been developed for FPPs to achieve the aforementioned functions efficiently, with the main scope of obtaining high performance and economic advantages. Introduction to Flow Field PlatesThe FPP, also known as the monopolar plate (in a single cell) and bipolar plate (BPP, when used in a stack), is one of the many important components of PEM fuel cell stacks as it supplies fuel and oxidant to the MEA, removes water, collects produced current and provides mechanical support for the single cells in the stack (Figure 1) AbstractThis review describes some recent developments in the area of flow field plates (FFPs) for proton exchange membrane fuel cells (PEMFCs). The function, parameters and design of FFPs in PEM fuel cells are outlined and considered in light of their ...

High temperature (HT) polymer electrolyte membrane fuel cells (PEMFC) – A review

“…Graphite plates have been traditionally used in fuel cells because of their chemical stability and high electrical conductivity, which makes them suitable for HT-PEMFC. Metallic plates are considered superior alternatives for graphite plates due to the reduction in cost, increased volumetric power density and higher mechanical strength [93]. The high temperature cell operation prevents the formation of liquid water in the cell, therefore, allows the use of a wider range of flow field designs without facing the water management problem.…”

“…Too much water and the electrocatalyst layer will flood which leads to a decrease in the fuel cell performance. As a result, design of the flow fields [93] and the material selection for the GDL is of paramount importance. When higher operating temperatures are used in the stack, the reaction product is water in the gas phase and as such it is much simpler to remove through a passive diffusion process.…”

“…When higher operating temperatures are used in the stack, the reaction product is water in the gas phase and as such it is much simpler to remove through a passive diffusion process. This is advantageous for several reasons, for example the design of the flow field plates becomes simpler which means that the stack design can be simplified [93]. However, it must be noted that the higher temperature will result in higher rates of degradation for the individual materials.…”

Carbon-Based Metal-Free Electrocatalysis for Energy Conversion, Energy Storage, and Environmental Protection

“…Fuel cells convert chemical energy directly into electricity by electrochemically oxidizing fuels (e.g., H 2 ) and reducing oxygen into water, providing instant power output with high energy conversion efficiencies and high power densities without any detrimental effects on the environment [139][140][141]. However, noble metal catalysts (e.g., Pt) are required for hydrogen oxidation at the anode and ORR at the cathode [142,143].…”

Fuel Cells: Technologies and Applications

“…The result is that an high effort in research and development is still needed to render this technology approachable, especially regarding the reduction of energy production costs [5][6][7] the use of new materials [8,9] and the improvement of conductivity mechanism in the electrolytes [10], also because the development of new materials remain in progress [11].…”