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The hydrogen bromine (H2-Br2) fuel cell system is an attractive system for electrical energy storage because of its high round-trip conversion efficiency, high power density capability, and anticipated low costs. The hydrogen-bromine fuel cell system can be operated in the acid or alkaline modes. The alkaline H2-Br2 fuel cell was evaluated because of its advantages over the acid system such as higher cell potential and low cost catalyst for the hydrogen evolution and oxidation reactions. A fuel cell was assembled to validate the feasibility of the alkaline system and evaluate its performance. The results confirmed that an alkaline H2-Br2 fuel cell has higher cell voltage and fast electrode reaction kinetics like in the acid system. However, the performance is currently limited by the low ionic conductivity of the membranes which is attributed to the slow diffusivity of the K+ ions.

Rhodium sulfide on carbon support (denoted as Rh2S3/C) was synthesized by refluxing of rhodium chloride (RhCl3) with ammonium thiosulfate. By thermal treatment in Ar, Rh2S3 can be transformed into different phases, such as Rh17S15, Rh3S4 and Rh, which were evident from XRD analysis. The particle size distribution of catalysts with the range from 3 to 12 nm (average 6 nm) was observed by transmission electron microscopy (TEM). The activity in terms of exchange current density (i0) for hydrogen oxidation (HOR) and hydrogen evaluation (HER) reaction in H2-saturated 1M hydrobromic acid (HBr) solution was obtained from the slope of Butler-Volmer plots.

In a hydrogen PEM fuel cell (PEMFC), liquid water is generated as a by-product (O2 + 4 H+ + 4 e- - 2H2O) at the cathode during operation. The presence of liquid water results in a two-phase (gas/liquid) condition in the porous media, such as, the gas diffusion and catalyst layers. In a direct methanol PEM fuel cell (DMFC), in addition to the two-phase condition in the cathode similar to that of a hydrogen PEMFC, another two-phase condition also exists in the anode when gaseous carbon dioxide is generated as a by-product (CH3OH + H2O - CO2 + 6 H+ + 6 e-) during operation. These two-phase conditions affect the transport rates of the reactants (oxygen and methanol/water) to the reactive sites in the electrodes. Knowledge of two-phase transport properties of the porous media used in PEMFCs and DMFCs is required to develop materials that will result in optimal fuel cell performance. This paper discusses the techniques that we have developed for measuring two-phase transport properties of porous media used in PEMFCs and DMFCs and the results obtained for some commercially available materials.