Antonio M. Chaparro

Degradation Study by Start-Up/Shut-Down Cycling of Superhydrophobic Electrosprayed Catalyst Layers Using a Localized Reference Electrode Technique

Degradation of a polymer electrolyte membrane fuel cell (PEMFC) with electrosprayed cathode catalyst layers is investigated during cyclic start-up and shut-down events. The study is carried out within a single cell incorporating an array of reference electrodes that enables measurement of cell current as a function of local cathode potential (localized polarization curves). Accelerated degradation of the cell by start-up/shut-down cycling gives rise to inhomogeneous performance loss, which is more severe close to the gas outlet and occurs predominantly during start-up. The degradation consists primarily of loss of cathode catalyst activity and increase in cell internal resistance, which is attributed to carbon corrosion and Pt aggregation in both anode and cathode. Cells with an electrosprayed cathode catalyst layer show lower degradation rates during the first 100 cycles, compared with those of a conventional gas diffusion electrode. This difference in behavior is attributed to the high hydrophobicity of the electrosprayed catalyst layer microstructure, which retards the kinetics of corrosion of the carbon support. In the long term, however, the degradation rate is dominated by the Pt/C ratio in the cathode catalyst layer.

Testing an isolated system powered by solar energy and PEM fuel cell with hydrogen generation

Abstract Photovoltaic systems are widely used to power telecommunications systems in remote locations, but this is restricted by the irregular availability of solar energy. A European collaboration is developing and testing an autonomous system that combines a photovoltaic power system in combination with an electrolyzer that uses surplus power to produce hydrogen, which can be used in a PEM fuel cell when there is insufficient solar energy.

EQCM Study of the Electrodeposition of Pt-WO3 and Its Catalytic Activity Towards the ORR

The electrodeposition process of WO3 and Pt-WO3 from acid solution has been investigated by means of Electrochemical Quartz Crystal Microbalance. Cyclic potential sweeps on Au substrate show that WO3 is a complex process with at least 5 different growth regimes, combining electrochemical and non electrochemical processes. Substoichiometric oxides and bronzes formation are involved in the deposition processes. When both Pt and WO3 precursors are present, Pt deposition is favoured and interaction between Pt and WO3 bronzes may explain this behaviour. Oxygen reduction (ORR) experiments on Pt-WO3 electrodeposited on glassy carbon and WO3 reveal high catalytic activity compared with platinum alone.

Properties of Catalyst Layers Prepared by Electrospray Deposition

Catalyst layers composed of Pt/C catalyst with ionomer (NafionR), for proton exchange membrane fuel cell (PEMFC) electrodes, have been prepared by electrospray deposition. Relevant properties for electrochemical fuel cell reactions are studied, related with total surface area (BET), platinum electroactive area, and single cell testing. Studies of surface area show lower values on electrospray deposited layers, compared with layers prepared by other methods (airbrush). It appears that a higher proportion of mesopores is filled with the ionomer, which reflects closer interaction between the ionomer and the catalyst aggregates. On the other hand, the electrochemical active area of Pt/C electrosprayed films shows values above those of films deposited by other common techniques or commercial electrodes. Electrode testing as cathodes in single cells shows better performance of electrosprayed layers due to lower electrode resistance, as a consequence of the improved distribution and interaction of the ionomer film among Pt/C catalyst aggregates.

Why portable electricity with hydrogen fuel cells

Abstract Reasons for the application of hydrogen and fuel cell in portable power systems are given. The fuel-cell energy generation concept has fundamental properties that may improve and complement current portable energy generators, mostly batteries, in many consumer applications. Fuel cells may become a solution to improve performance, autonomy, and safety of future portable devices. By analyzing the fundamental properties of batteries and fuel cells, it is concluded that both electrochemical devices may have a complementary role in future portable electronics. Batteries will be more appropriate for low-power applications (