Peak power PEMFC

Since many years now, Morse et al (Lawrence Livermore National Laboratory) have been working on SOFCs and PEMFCs [51]. They combined thin film and MEMS technologies to fabricate miniature FCs. A silicon modular design served as the platform for FCs based on either PEM or SO membrane. In 2002, the PEM cell yielded a computed peak power of 37 mW cm at 0.45 V and 40 °C whereas the SOFC reached 145 mW cm at 0.35 V and 600 °C. Since 2002, the UltraCell company has an exclusive license with Lawrence Livermore National Laboratory to exploit their technology to develop commercial FCs. 

Watanabe et al. [26] and Antonucci et al. [27] investigated the reduction of water above 100°C to maintain proton conductivity by incorporating hydrophilic micronsized metal oxide particles such as SiO and TiO into Nafion with limited success. Peak power densities of 250 and 150 mW-cm" in oxygen and air, respectively, were reported. Mauritz et al. used an in situ sol-gel technique to intfoduce a polymeric form of SiO into Nafion to form composite membranes [28]. Recently, Adjemian et al. utilized Mauritz synthetic procedure to fabricate Nafion/SiOj membranes and demonstrated that water management within Nafion improved at elevated temperatures in a 3-atm pressurized H /O PEMFC [29]. Various PFSAs, including Nafion and Aciplex, were studied as pure and in the SiO composite membranes for operation in H /O PEMFCs from 80 to 140°C. These cells demonstrated acceptable current densities, for instance, Nafion-IH/SiO and Nafion-112/Si02 achieved 850 and 1280 mA cm", respectively, at 0.4 V up to at least 130°C, 3 atm pressure, and 100% relative humidity. 

Furthermore, in 2001, Ballard entered an alliance with Victrex to produce two new membrane alternatives. One membrane is based on sulfonated poly(arylether) ketone (a variant of PEEK) supplied by Victrex, which may be better suited to PEMFC fabrication applications. In March 2002, U.S. Patent 6,359,019 was issued to Ballard Power for a graft-polymeric membrane in which one or more trifluorovinylaromatic monomers are radiation graft polymerized to a preformed polymeric base. The strucmres of BAM membranes have been studied by way of small-angle neutron scattering (SANS) [97]. The study of the ionomer peak position suggests the existence of relatively small ionic domains compared to Nalion, despite large water content. Phase separation in the polymer matrix is possibly crucial for the membrane s mechanical and transport properties. 

---