Aquivion® PFSA

Aquivion PFSA mebrane performance data, http //www.solvaysites.com/sites/ solvayplastics/EN/specialty polymers/Specialties/Pages/Aquivion PFSA.aspx... 

Similar PFSA materials have been developed by other companies such as the Asahi chemical company (trade name Aciplex), the Asahi glass company (trade name Flemion), Solvay (trade name Hyflon and Aquivion), Fumatech (trade name Fumion), 3 M, the Dow chemical company and others. These materials are sometimes differing in the equivalent weight or the chemical nature of the side chains [3]. 

A modification of the polymer that has been adopted by various groups is to have shorter side chains as compared to Nafion. Short side chains increase the crystallinity of the PFSA, thus reducing the solubility. Solvay Solexis has developed Aquivion, a membrane based on Hyflon, which is a copolymer of Teflon and sulfonyl fluoride vinyl ether with low EW (790-870) and good crystallinity, with proton conductivity values in the order of 30 mS cm at 120°C, 30% RH [22]. A similar approach is followed by 3M, who have shown 580 EW membranes approaching 100 mS cm at 120°C and RH 50% [23]. Gore recently reported values >50 mS cm at 30% RH and > 100 mS cm 50% RH with a new, undisclosed ionomers [24]. DuPont recently presented results on MEAs with new ionomer that showed a much reduced dependence on the RH as compared to Nafion-based membranes [17]. 

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... 

Stack tests on Aquivion-containing MEAs have shown that only a moderate decrease in performance occurs at 110 °C, 1.5 bar abs. with 33 % RH. MEA hydration in the stack at intermediate temperature was mainly assured by the internal humidification and the back-diffusion of the water from the cathode to the anode through the thin (30 pm) low equivalent weight (790 g eq ) PFSA membrane. In the stack, the new Aquivion E79-03S membrane showed high conductivity, good water retention, and mechanical properties above 100 °C as compared to the conventional PFSA membranes and appropriate characteristics for a rapid startup in a cold environment as well as suitable operation in duty cycles. These promising characteristics were supported by improved MEA structures,... 

Proton conductivity in PFSA membranes depends upon the polymer EW (nrrmber of charge carriers), and the hydration number (A, number of water molecrrles/srrlforric acid group), polymer stracture, membrane morphology and temperatirre, all of which affect proton mobility. The proton conductivity of some recent PFSA membrane materials is shown in Fig. 2.3-2 5. Figure 2.3 illustrates for 3MTM PFSA membranes the effect of polymer EW and hydration niunber on proton conductivity at 80 °C, Fig. 2.4 displays the variation of proton conductivity of Aquivion membranes with temperature and relative hirmidity, and Fig. 2.5 shows the conductivity of Nafion NR-211 at 30 °C, 50 °C and 80 °C over a range of relative humidity values. 

The success of DuPont s Nafion spurred the development of other polymeric materials with similar chemical architecture. The most notable material developments have been the Dow experimental membrane (Dow Chemicals), Flemion (Asahi Glass), Aciplex (Asahi Kasei), as well as Hyflon Ion and its most recent modification Aquivion (SolviCore). In addition to excellent ionic conductivity, materials of the PFSA family, illustrated in Figure 2.2, exhibit exceptional stability and durability in highly corrosive acidic environments, owing to their Teflon-like backbone (Yang et al., 2008 Yoshitake and Watakabe, 2008). 

Systems showed significant improvements in fnel cell performance using SSC-PFSA monbranes obtained from the Dow Chanical Company. Merlo et al. reported that the fuel ceU performance of Hyflon Ion-based MEAs at medium (75°C) and high (120°C) tanperatures demonstrated extronely good power output. Stassi et al. reported that a maximum power density of about 870 mW/cm was obtained with Aquivion at 130 (3 bar, abs. 100% RH). This value was significantly better compared to the power density of 620 mW/cm measured with Nafion membrane. ... 

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