Structure, Property, and Performance of Catalyst Layers in Proton Exchange Membrane Fuel Cells

Abstract

Catalyst layer (CL) is the core component of proton exchange membrane (PEM) fuel cells, which determines the performance, durability, and cost. However, difficulties remain for a thorough understanding of the CLs’ inhomogeneous structure, and its impact on the physicochemical and electrochemical properties, operating performance, and durability. The inhomogeneous structure of the CLs is formed during the manufacturing process, which is sensitive to the associated materials, composition, fabrication methods, procedures, and conditions. The state-of-the-art visualization and characterization techniques are crucial to examine the CL structure. The structure-dependent physicochemical and electrochemical properties are then thoroughly scrutinized in terms of fundamental concepts, theories, and recent progress in advanced experimental techniques. The relation between the CL structure and the associated effective properties is also examined based on experimental and theoretical findings. Recent studies indicated that the CL inhomogeneous structure also strongly affects the performance and degradation of the whole fuel cell, and thus, the interconnection between the fuel cell performance, failure modes, and CL structure is comprehensively reviewed. An analytical model is established to understand the effect of the CL structure on the effective properties, performance, and durability of the PEM fuel cells. Finally, the challenges and prospects of the CL structure-associated studies are highlighted for the development of high-performing PEM fuel cells. Graphical abstract

Optimized mass transfer in a Pt-based cathode catalyst layer for PEM fuel cells

“…Apart from electrochemical techniques, structural characterization such as pore size distribution analysis and contact angle measurement is essential to elucidate the gas/liquid transport behavior in the CL. 63 The pore structure of CLs is highly inhomogeneous and irregular, even though many studies ideally treat the pores in the shapes of cylinders, spheres, slits, and cavities. The critical pore structure-related parameters such as pore size distribution, which can be experimentally determined, are all vital to understanding the transport and electrochemical phenomena in CLs (Fig.…”

In Situ Construction of a Nanostructured Ultrathin Catalyst Layer on Both Sides of a Membrane toward Fuel Cell Application

“…Cross-sectional-view SEM images reveal that the membrane is sandwiched by CLs with a thickness of merely 197 ± 32 nm (Figures 2a,b and S3b and S5), much thinner than that of conventional ones (5−10 μm) fabricated by the ink-based approach in the literature. 5,12 SEM images reveal that the major structural features of the peony flower are well retained after the deposition of Pt (Figures 2c,d and S6a,b). The resulting Pt/Pd nanoflowers were characterized by HAADF-STEM in conjunction with EDX analysis.…”

“…The formed CCMs generally exhibit several disadvantages, including low activity, unaffordable Pt loading (0.2–0.6 mg Pt cm MEA –2 ), − and inefficient mass transportation due to the tortuous and lengthy diffusion pathway in the micrometer-scale thick (ca. 5–10 μm) − catalyst layer (CL).…”

Preparation of Ti/SnO2–Sb–Ir–Mn Electrodes with Low Iridium Content for a Highly Efficient and Stable Oxygen Evolution Reaction

“…Electrodes for the OER are widely used in the electrochemical industry, including hydrogen production, fuel cell, electrochemical descaling, and organic wastewater treatment . There have been a great number of candidates applied to the OER, such as nickel phosphide, transition metal oxide and hydroxide, NiFe selenide, and cobalt sulfide, among which is the titanium based metal oxide anode, known as a dimensionally stable anode (DSA), which has been researched for its excellent ability for corrosion resistance .…”