Sabrina C. Zignani

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.

Nickel–Iron/Gadolinium-Doped Ceria (CGO) Composite Electrocatalyst as a Protective Layer for a Solid-Oxide Fuel Cell Anode Fed with Biofuels

The performance and reliability of a commercial solid‐oxide fuel cell (SOFC) with the anode coated by a protective catalytic layer is demonstrated. Physico‐chemical and electrochemical characterizations of a Ni–Fe/gadolinium‐doped ceria (CGO) electrocatalyst forming the protective layer are reported. The anode layer was prepared by using a procedure that favors the interaction between Ni and Fe. Power densities approaching 0.3 W cm−2 for the SOFC cell fed with dry organic fuels were obtained. A time test was performed in the presence of a large flow rate of dry organic fuels under operating conditions (0.8 V) showing appropriate fuel flexibility for the device. The resistance to sulfur contamination was verified by feeding increasing amounts of H2S. The cell showed only moderate performance losses until 80 ppm of sulfur contaminant.