Catalysts For Change: The Key Trends for PEM Fuel Cell Catalysts
Dec 07, 2022 Dr Conor O'Brien
Catalysts are critical for the performance of proton exchange membrane (PEM) fuel cells. As the trend towards zero-emission vehicles continues, fuel cell electric vehicles (FCEVs) are projected to grow accordingly as a market sector. The annual demand for typical catalytic materials, such as platinum group metals, is set to exceed 3.5 metric tonnes by 2033. In this article, IDTechEx presents an overview of the catalytic materials market and assesses the key trends for this sector over the coming decade.
IDTechEx covers the electric vehicle industry comprehensively, detailing battery electric vehicles (BEVs) and FCEVs. The FCEV research is segmented by passenger cars, light commercial vehicles (vans), heavy-duty trucks, and city buses. They have released a new report, "Materials for PEM Fuel Cells 2023-2033", which includes granular 10-year forecasts segmented by vehicle type for key fuel cell components and materials in terms of both units and volume, while also detailing the value associated with each segmentation.
Catalysts are necessary for PEM fuel cells to enable the chemical reaction to occur effectively at sub-100°C temperatures, allowing the aqueous conditions that the PEM requires for proton transport. Typically, platinum and other platinum group metals (PGMs) are utilized as catalysts; however, the high cost of these precious metals is inhibitive to the cost reduction of the overall fuel cell stack.
Graphic representation of the PEM, CCM, and MEA - showcasing the need for succinct terminology to discuss catalysts in fuel cells. Further discussion can be found in the IDTechEx market report "Materials for PEM Fuel Cells 2023-2033". Source: IDTechEx
When discussing catalysts for PEM fuel cells, it is imperative to define the area of interest succinctly. While 'catalyst' is an all-encompassing term, IDTechEx notes that catalyst-coated membranes (CCM) cannot be discounted from the conversation. CCMs account for the membrane material with an integrated catalytic layer. This CCM is often sandwiched between gas diffusion layers (GDL) to create a fully integrated component known as a membrane electrode assembly (MEA). For the purpose of this article, IDTechEx will cover the trends seen for the catalytic material itself.
Primarily, there is a drive to reduce the fuel cell stack cost. Given the high value of PGMs, increasing the catalytic activity of the metals would reduce the volume of precious metal required. This can be done by exploring alternative metals such as the Pt3Ni alloy or gold nanoparticles. Another option is to change the form factor of the Pt catalyst, optimizing the number of active catalytic sites. The IDTechEx report covers all of these developments in detail, alongside a review of the targets set by government bodies and an assessment of the current and future loading employed by major players in the value chain.
The reduction of catalytic poisoning in the fuel cell would allow the less precious metal to be used in the stack. Poisoning occurs when carbon monoxide permanently bonds to the platinum catalyst, decreasing desirable catalytic activity. Carbon monoxide (CO) is an unwanted hydrogen gas component produced by steam-reforming hydrocarbons. It should be noted that mass production of pure hydrogen via electrolysis can negate the issue of CO contamination. Other attempts to limit catalytic poisoning involve altering the shape of the catalyst nanoparticles, with certain molecular arrangements of the catalyst providing sites that are less likely to be contaminated by CO bonding.
A major aspect of reducing the catalyst cost is finding alternative materials to the incumbent precious metal - platinum. Some of these materials have already been mentioned, such as the Pt3Ni alloy and Au nanoparticles. Metal/nitrogen/carbon (MNC) catalysts have been proposed as promising alternatives. Although volumetric catalytic activity is only 10% of that seen for Pt, increased loading of MNC catalysts has been proposed as a solution to mitigate this concern due to lower costs. Leading providers of catalyst for fuel cells offer a range of materials, from Pt to IrO2. The report from IDTechEx details the key suppliers of PGM catalysts to OEMs and forecasts the demand for PGM materials and the value associated with integrating these metals into a CCM.
For more details on the materials demand, trends, and emerging novel alternatives to the incumbents for PEM fuel cells, please see the IDTechEx market report "Materials for PEM Fuel Cells 2023-2033".