(506b) Characterization of HBr PEM Electrolyzer for Hydrogen Production

Recently, many efforts are captured on the highly efficient and low costly processes for bulk production of hydrogen. Traditionally, hydrogen could be extracted from hydrocarbons via steam reforming, water gas shift reaction and coal gasification, or from water via algae biochemical reactions, electrolysis or thermochemical reactions. In the indirect splitting of water via thermochemical reactions, not only pure hydrogen and zero carbon species emissions are produced, but also, recovering heat from the nuclear reactor, overall efficiency from heat to hydrogen could approach 50%.

The calcium-bromide-based cycle, for example the known UT-3 cycle [1-4], is one of promising thermo-chemical cycles. To eliminate the drawback of high pressure drop in the step of regeneration of bromine in the iron oxide fix bed reactor in the UT-3 cycle, single electrochemical step [5-8] could directly be utilized to recover the bromine from hydrogen bromide. In our last paper [7], direct electrolysis of gaseous hydrogen bromide to bromine and hydrogen was successfully demonstrated in a proton exchange membrane (PEM) reactor on. Anhydrous gaseous hydrogen bromide was fed at the anode to promote mass transfer, while hydrogen is evolved at the cathode. In this work, a model HBr PEM electrolytic reactor was characterized with respects to analyzing individual voltage losses, developing non-Pt electrocatalysts, and investigating water effects. Temperature and pressure on the equilibrium cell potential are modeled with VLE modeling in OLI lab of Aspen. A mathematical model was used to predict the water content distribution in the Nafion membrane and thus the membrane resistance under polarization conditions. It was then verified with the current interruption data. Overpotential of hydrogen evolution reaction at cathode is then verified in the hydrogen pump. Finally, voltage losses in the HBr cell are quantified from the total polarization curve. Effects of pressure, temperature and electrocatalysts on the cell polarization are then discussed.

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