Overcoming the Electrode Challenges of High-Temperature Proton Exchange Membrane Fuel Cells

Abstract

Proton exchange membrane fuel cells (PEMFCs) are becoming a major part of a greener and more sustainable future. However, the costs of high-purity hydrogen and noble metal catalysts alongside the complexity of the PEMFC system severely hamper their commercialization. Operating PEMFCs at high temperatures (HT-PEMFCs, above 120 °C) brings several advantages, such as increased tolerance to contaminants, more affordable catalysts, and operations without liquid water, hence considerably simplifying the system. While recent progresses in proton exchange membranes for HT-PEMFCs have made this technology more viable, the HT-PEMFC viscous acid electrolyte lowers the active site utilization by unevenly diffusing into the catalyst layer while it acutely poisons the catalytic sites. In recent years, the synthesis of platinum group metal (PGM) and PGM-free catalysts with higher acid tolerance and phosphate-promoted oxygen reduction reaction, in conjunction with the design of catalyst layers with improved acid distribution and more triple-phase boundaries, has provided great opportunities for more efficient HT-PEMFCs. The progress in these two interconnected fields is reviewed here, with recommendations for the most promising routes worthy of further investigation. Using these approaches, the performance and durability of HT-PEMFCs will be significantly improved.

Catalyst Development for High‐Temperature Polymer Electrolyte Membrane Fuel Cell (HT‐PEMFC) Applications

“…[179] Thereby, a retention of up to 66% in voltage, being in the same range for other Fe-N-C tested in HT-PEMFCs, [184] ranks higher than most Fe-N-C cathodes operated for LT-PEM. [175,185,186] Fe-N-C shows the most comparable SAC ORR activity to commercial Pt-C in acid, [187] but their HT-PEMFC application has been limited due to their lower volumetric activity. Fe-N-C electrodes are ≈ 5-10 times thicker than Pt-C catalyst layers, [188] to compensate for the decreased intrinsic performance toward the ORR.…”

“…[ 179 ] Thereby, a retention of up to 66% in voltage, being in the same range for other Fe–N–C tested in HT‐PEMFCs, [ 184 ] ranks higher than most Fe–N–C cathodes operated for LT‐PEM. [ 175,185,186 ]…”

A Critical Review on Hydrogen Based Fuel Cell Technology and Applications

“…Alternative materials under investigation include hydrocarbon‐based materials like sulfonated poly(phenylene) and perfluorinated ionomers, as well as inorganic materials such as ceramic or proton exchange membranes. The development of membranes capable of operating at higher temperatures is crucial for improving FC efficiency and expanding their applicability in various fields [255,256] . The membranes that can withstand higher temperatures can reduce the need for expensive cooling systems, simplify system design, and enable the use of alternative fuels [257] .…”

Construction of Zr-Metal–Organic Frameworks-Based Composite Materials toward Anhydrous Proton Conduction and Photocatalytic CO2 Reduction

“…Proton exchange membranes (PEMs) are an important component of PEM fuel cells (PEMFCs) and need to have high proton conductivity, thermal stability, and chemical/physical stability. – In the 1960s, commercial perfluoro sulfonic acid membranes (Nafion) with conductivities up to 10 –1 S cm –1 emerged. However, this series of membranes were costly, and their electrical conductivity were poor at high temperatures. , From the 1970s to the 1980s, many inorganic materials emerged, such as metal oxides, solid acids, and ceramic oxides, which have proton conductivities up to 10 –2 S cm –1 but poor thermal stability. , Nowadays, silicon dioxide, graphene, functionalized carbon nanotubes and metal–organic frameworks (MOFs) have been used to prepare high-performance proton conducting materials, which have excellent development prospects. – Among them, MOFs show great proton conductivity by functional improvement of organic ligands and careful selection of metal ions.…”