Electrocatalyst supports membrane electrode assembly

Recently, taking advantage of the very narrow size distribution of the metal particles obtained, microemulsion has been used to prepare electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs) Catalysts containing 40 % Pt Ru (1 1) and 40% Pt Pd (1 1) on charcoal were prepared by mixing aqueous solutions of chloroplatinic acid, ruthenium chloride and palladium chloride with Berol 050 as surfactant in iso-octane. Reduction of the metal salts was complete after addition of hydrazine. In order to support the particles, the microemulsion was destabilised with tetrahydrofurane in the presence of charcoal. Both isolated particles in the range of 2-5 nm and aggregates of about 20 nm were detected by transmission electron microscopy. The electrochemical performance of membrane electrode assemblies, MEAs, prepared using this catalyst was comparable to that of the MEAs prepared with a commercial catalyst. 

Typical results were obtained with a membrane-electrode assembly (MBA) consisting of a Nafion 117 membrane on which are pressed the anodic electrocatalysts (Pt or Pt-based catalysts dispersed on a high surface area carbon support) and the cathodic catalyst (usually Pt/C with metal loading from 40 % to 60 %). An example of the electrical characteristics of a DEFC with Pt/C, PtSn/C or PtSnRu/C anode catalysts is given in Fig. 2. 

Table 23.1. Electrocatalyst cycle and metrics [44]. (Reproduced from United States Department of Energy. DOE cell component accelerated stress test protocols for PEM fuel cells electrocatalysts, supports, membranes, and membrane electrode assemblies. 2007. With permission from DOE.)...

Aquivion E87-12S short-side chain perfluorosulfonic acid (SSC-PFSA) membrane with equivalent weight (EW) of 870 g eq and 120 pm thickness produced by Solvay Specialty Polymers was tested in a polymer electrolyte membrane water electrolyser (PEMWE) and compared to a benchmark Nation N115 membrane (EW 1100 g eq ) of similar thickness [27]. Both membranes were tested in conjunction with in-house prepared unsupported Ir02 anode and carbon-supported Pt cathode electrocatalyst. The electrocatalysts consisted of nanosized Ir02 and Pt particles (particle size 2-4 nm). The electrochemical tests showed better water splitting performance for the Aquivion membrane and ionomer-based membrane-electrode assembly (MEA) as compared to Nafion (Fig. 2.21). Lower ohmic drop constraints and smaller polarization resistance were observed for the electrocatalyst-Aquivion ionomer interface indicating a better catalyst-electrolyte interface. A current density of 3.2 A cm for water... 

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