A.S. Aricò

Investigation of IrO2/Pt Electrocatalysts in Unitized Regenerative Fuel Cells

IrO2/Pt catalysts (at different concentrations) were synthesized by incipient wetness technique and characterized by XRD, XRF, and SEM. Water electrolysis/fuel cell performances were evaluated in a 5 cm2 single cell under Unitized Regenerative Fuel Cell (URFC) configuration. The IrO2/Pt composition of 14/86 showed the highest performance for water electrolysis and the lowest one as fuel cell. It is derived that for fuel cell operation an excess of Pt favours the oxygen reduction process whereas IrO2 promotes oxygen evolution. From the present results, it appears that the diffusion characteristics and the reaction rate in fuel cell mode are significantly lower than in the electrolyser mode. This requires the enhancement of the gas diffusion properties of the electrodes and the catalytic properties for cathode operation in fuel cells.

Composite Anode Catalysts Based on PtRu and Metal Oxide Nanoparticles for DMFCs

A composite anode was investigated with the aim of enhancing the performance of direct methanol fuel cells (DMFCs). Fine iridium oxide nanoparticles were synthesized by a sulfite complex method. These IrO2 nanoparticles were mixed by sonication with a 50% PtRu/C catalyst prepared by the same procedure, considered as benchmark anode catalyst. A significantly higher performance was recorded for the composite electrode compared to the bare one based only on PtRu/C. The results confirm that the electrocatalytic activity is related to the characteristics of water displacement of the additive, evidencing that a multifunctional catalyst can operate better than PtRu for methanol oxidation since this multi-step process requires different functionalities to speed up the reaction rate.