Thermal efficiency of solid electrolyte fuel cells with mixed conduction

The effect of mixed anionic and n-type electronic conduction in solid electrolytes on the thermal efficiency of a fuel cell system was analyzed quantitatively. The mixed conduction observed when electrolytes based on ceria are used in H₂/air fuel cell applications lowers the maximum attainable cell thermal efficiency to below 40%. Neither the zirconia nor the ceria based solid oxide electrolytes studied to date can be used in a low temperature (700 °C) system that meets simultaneously the requirements of power density and thermal efficiency for electric utility power plants. The material properties required for an advanced fuel cell power plant solid electrolyte were derived in terms of the ionic conductivity and the Schmalzried parameters P and P : σ_ion > 0.033 (Ω-cm)⁻¹, P > 10³ atm., P < 10⁻²³ atm. at 700 °C.     

Obtention and evaluation of polyethylene-based solid polymer electrolyte membranes for hydrogen production

New cation exchange membranes were developed, intended for use as solid polymer electrolyte (SPE) for the production of hydrogen by water electrolysis. They were produced by radiation grafting of styrene groups on a polyethylene matrix, followed by chemical sulphonation of the resulting polymer. They can be reinforced by an organic polymer fabric, which largely improves their mechanical properties. For such membranes, about 0.1 mm thick, resistivities as low as 60 Ω cm have been achieved, which is of the same order of magnitude as the values for commercially available SPEs. It can be assumed that the nature of the starting materials, and the production process, should make these membranes much less costly than the perfluorinated-hydrocarbon-based polymers which, so far, have been most generally used as SPEs. During life test experiments, at a current density ca. 2 kA m^?2, the membranes described herein showed no noticeable degradation of electrical or mechanical properties after a 3000 h run. Research is now in progress to design and test electrodes and ancillary equipment for a water electrolyzer incorporating such SPE membranes.     

Electrochemical solar cells with layer-type semiconductor anodes. Performance of n-MoSe2 cells

The output characteristics and the long-term performances of n-MoSe₂ (I^?, I₂) electrochemical solar cells have been investigated. It has been confirmed that, by analogy with other layer-type, d-band transition metal dichalcogenide systems, the surface state of the semiconductor plays a key role in the behaviour of the cell. With ‘smooth’ crystal samples, fill factor and efficiency values of the order of 0.6 and 6%, respectively, have been obtained under AM1 illumination. Such performances are, however, drastically reduced if ‘irregular’ crystal samples are used.Control of these undesirable surface state effects has been attempted by chemical treatments specific to the unsaturated transition metal atoms exposed to the electrolyte at the edge sites. Finally, the stability of n-MoSe₂ I^?, I₂) cells under long time operation, has also been evaluated.     

Manganese dioxide — a review of a battery chemical part I. Chemical syntheses and x-ray diffraction studies of manganese dioxides

This review is concerned with the synthesis of manganese dioxide by chemical methods and by the activation of natural ores. Chemical synthesis usually     

Manganese dioxide — a review of a battery chemical Part II. Solid state and electrochemical properties of manganese dioxides

A literature survey indicated that the properties such as electrical conductivity, magnetic susceptibility, thermal decomposition temperature and water content influence the activity of manganese dioxides.Infrared spectroscopy is considered as a convenient analytical tool with which to characterize the various crystal phases of the dioxides. Increasing attention has also been given to predicting the potentials of the system (MnO₂)_1?r. MnOOH_r during electrochemical reduction with a view to understanding the observed discharge characteristics.Further, attempts are being made to correlate the activity of the dioxides with their structural features.