Irene Gatto

Towards Highly Performing and Stable PtNi Catalysts in Polymer Electrolyte Fuel Cells for Automotive Application

In order to help the introduction on the automotive market of polymer electrolyte fuel cells (PEFCs), it is mandatory to develop highly performing and stable catalysts. The main objective of this work is to investigate PtNi/C catalysts in a PEFC under low relative humidity and pressure conditions, more representative of automotive applications. Carbon supported PtNi nanoparticles were prepared by reduction of metal precursors with formic acid and successive thermal and leaching treatments. The effect of the chemical composition, structure and surface characteristics of the synthesized samples on their electrochemical behavior was investigated. The catalyst characterized by a larger Pt content (Pt3Ni2/C) presented the highest catalytic activity (lower potential losses in the activation region) among the synthesized bimetallic PtNi catalysts and the commercial Pt/C, used as the reference material, after testing at high temperature (95 °C) and low humidification (50%) conditions for automotive applications, showing a cell potential (ohmic drop-free) of 0.82 V at 500 mA·cm−2. In order to assess the electro-catalysts stability, accelerated degradation tests were carried out by cycling the cell potential between 0.6 V and 1.2 V. By comparing the electrochemical and physico-chemical parameters at the beginning of life (BoL) and end of life (EoL), it was demonstrated that the Pt1Ni1/C catalyst was the most stable among the catalyst series, with only a 2% loss of voltage at 200 mA·cm−2 and 12.5% at 950 mA·cm−2. However, further improvements are needed to produce durable catalysts.

Comparative Investigation on Nano-Sized SiO2 as a Filler for Proton Exchange Membranes (PEM) Fuel Cells

A commercial hygroscope SiO2 was used as an inorganic filler in a Nafion ® polymeric matrix. The influence on chemical-physical properties and electrochemical behaviour in Polymer Electrolyte Fuel Cells (PEFCs) was investigated in terms of amount and particle size of the introduced inorganic compound. Such SiO2 has got a good water retention capacity that improves the water uptake and contributes to improve the stiffness of the developed membranes, probably making more efficacy in the medium temperature operation. Current density values of about 720mW/cm 2 and 640W/cm 2 at 80°C and 110°C (0.6V and 100%RH), respectively were reached from the NSiO2 membrane containing a 5%wt/wt of oxide with a particle size of 7 nm. Such result compared to a home-made bare Nafion membrane showed an important improvement, high lightening the benefit of the inorganic filler when PEFC operates at medium temperature.

Double filler reinforced ionomers: a new approach to the design of composite membranes for fuel cell applications

A novel approach to mechanically reinforce polymer electrolyte membranes for fuel cells was developed by using hydrophilic zirconium phosphate (ZP) and hydrophobic fluoroalkyl zirconium phosphate (ZF) as a two-component mixed filler of a short-side-chain perfluorosulfonic acid (PFSA) membrane. Composite membranes filled with 10 wt% ZF and 5 wt% ZP have a strongly enhanced elastic modulus (E) and yield stress (σY) with respect to the unmodified PFSA (ΔE/E ∼ 300%, ΔσY/σY ∼ 95% at 70 °C and 80% relative humidity (RH)) and to the single filler membranes with optimized ZP or ZF loadings. In the RH range 50–95%, the in-plane conductivity of the mixed filler membrane is comparable with that of the unmodified PFSA, both at 80 and 110 °C, in spite of a lower water content. At 50% RH, the mixed filler membrane shows better fuel cell performance in H2/air than the neat PFSA in terms of higher OCV, lower H2 crossover and greater power density, with peaks of 0.82 W cm−2 at 80 °C, and 0.70 W cm−2 at 110 °C.

Solid-State Materials for Hydrogen Storage

Hydrogen (H2) is a promising replacement energy carrier and storage molecular due to its high energy density by weight. For the constraint of size and weight in vehicles, the onboard hydrogen storage system has to be small and lightweight. Therefore, a lot of research is devoted to finding an efficient method of hydrogen storage based on both mechanical compression and sorption on solid-state materials. An overview of the current research trend and perspectives on materials-based hydrogen storage including both physical and chemical storage is provided in the present paper. Part of this chapter was dedicated to recent results on two innovative materials: hybrid materials based on manganese oxide anchored to a polymeric matrix and natural volcanic powders. A prototype H2 tank, filled with the developed hybrid material, was realized and integrated into a polymer electrolyte membrane (PEM) single fuel cell (FC) demonstrating the material capability to coupling with the FC.

Modifications of Sulfonic Acid-Based Membranes

Aiming at intermediate temperature operation (100–150 °C), composite polymer electrolyte membranes consisting of perfluorosulfonic acid (PFSA) ionomer and inorganic fillers, particularly short-side chain perfluorosulfonic membranes, e.g., Aquivion® membranes with an equivalent weight of 790–850 g eq−1 and their composites with inorganic fillers represent a practical approach to advanced membrane materials. This chapter is devoted to an updated review of the methodologies and materials including their practical applications in direct alcohol fuel cells, water electrolysers, and automotive hydrogen fuel cells. An analysis of the basic operation mechanism of such materials is provided and the characteristic performances achieved under intermediate temperature operation are reviewed. The influence of the surface chemistry and acid–base characteristics of the inorganic fillers is also discussed.