Alessandro Stassi

Synthesis of Pd3Co1@Pt/C Core‐Shell Catalysts for Methanol‐Tolerant Cathodes of Direct Methanol Fuel Cells

A composite Pd-based electrocatalyst consisting of a surface layer of Pt (5 wt.%) supported on a core Pd3Co1 alloy (95 wt.%) and dispersed as nanoparticles on a carbon black support (50 wt.% metal content) was prepared by using a sulphite-complex route. The structure, composition, morphology, and surface properties of the catalyst were investigated by XRD, XRF, TEM, XPS and low-energy ion scattering spectroscopy (LE-ISS). The catalyst showed an enrichment of Pt on the surface and a smaller content of Co in the outermost layers. These characteristics allow a decrease the Pt content in direct methanol fuel cell cathode electrodes (from 1 to 0.06 mg cm(-2)) without significant decay in performance, due also to a better tolerance to methanol permeated through the polymer electrolyte membrane.

Investigation of Supported Pd-Based Electrocatalysts for the Oxygen Reduction Reaction: Performance, Durability and Methanol Tolerance

Next generation cathode catalysts for direct methanol fuel cells (DMFCs) must have high catalytic activity for the oxygen reduction reaction (ORR), a lower cost than benchmark Pt catalysts, and high stability and high tolerance to permeated methanol. In this study, palladium catalysts supported on titanium suboxides (Pd/TinO2n–1) were prepared by the sulphite complex route. The aim was to improve methanol tolerance and lower the cost associated with the noble metal while enhancing the stability through the use of titanium-based support; 30% Pd/Ketjenblack (Pd/KB) and 30% Pd/Vulcan (Pd/Vul) were also synthesized for comparison, using the same methodology. The catalysts were ex-situ characterized by physico-chemical analysis and investigated for the ORR to evaluate their activity, stability, and methanol tolerance properties. The Pd/KB catalyst showed the highest activity towards the ORR in perchloric acid solution. All Pd-based catalysts showed suitable tolerance to methanol poisoning, leading to higher ORR activity than a benchmark Pt/C catalyst in the presence of low methanol concentration. Among them, the Pd/TinO2n–1 catalyst showed a very promising stability compared to carbon-supported Pd samples in an accelerated degradation test of 1000 potential cycles. These results indicate good perspectives for the application of Pd/TinO2n–1 catalysts in DMFC cathodes.

Platinum Ruthenium Catalysts Supported on Carbon Xerogel for Methanol Electro‐Oxidation: Influence of the Catalyst Synthesis Method

A high surface area, highly mesoporous carbon xerogel was synthesised and used as a support in the preparation of platinum–ruthenium catalysts by different synthetic routes. The platinum–ruthenium carbon xerogel catalysts were physico‐chemically characterised and used for the chemical electro‐oxidation of methanol. The synthetic routes pursued included: 1) impregnation with metal chloride precursors and reduction with two different reducing agents: sodium borohydride and formic acid; 2) a microemulsion‐based method and 3) a sulfite complex method, which led to catalysts with different physico‐chemical features that strongly influence their catalytic behaviour towards methanol oxidation. The electro‐oxidation of methanol was found to depend on both the crystal size and the extent of active phase reduction as well as on the platinum concentration on the catalyst surface, which were maximised for the impregnation method and reduction with formic acid.

A Novel Anode Based on Ni-Modified Perovskite for Direct Alcohol Solid Oxide Fuel Cells

A Ni-modified La0.6Sr0.4Fe0.8Co0.2O3 / Ce0.9Gd0.1O2 catalyst was prepared by incipient wetness. The product thus obtained was calcined at 1100°C for 2 h in static air. After thermal activation, Ni was mainly present as highly dispersed La2NiO4 on the surface of perovskite surface. The thermal reduction at 800 °C caused the occurrence of metallic Ni on the surface. Surface area was determined by BET measurement. The catalyst was used as anode in IT-SOFCs fed with methanol. Studies under steam reforming, partial oxidation and autothermal reforming of methanol were carried out at 800°C. A comparison was made between the performance of SOFCs fed with syngas or methanol. The results with methanol are promising both in terms of energy density as well as suitable performance for portable power sources.

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.

Investigation of a Passive DMFC Mini-Stack at Room Temperature

Direct Methanol Fuel Cells (DMFCs) are promising candidates for portable electric power sources because of their high energy density, lightweight, compactness, simplicity as well as easy and fast recharging. Recently, the attention has been focused on portable applications with passive-feed DMFCs. Under this configuration, DMFCs operate without any external device for feeding methanol and blowing air into the cells. An investigation of properties and operating parameters of a passive DMFC monopolar mini-stack, such as catalyst loading and methanol concentration, was carried out. From this analysis, it was derived that a proper Pt loading is necessary to achieve the best compromise between electrode thickness and number of catalytic sites for the anode and cathode reactions to occurs at suitable rates. Methanol concentrations ranging from 1 M up to 10 M (40 vol%) and an air-breathing operation mode were investigated. A maximum power of 225 mW was obtained at ambient conditions for a three-cell stack, with an active single cell area of 4 cm2 corresponding to a power density of about 20 mW cm-2.