(348d) Electrochemical Generation of Hydrogen Via Gas Phase Oxidation of Sulfur DI Oxide and Hydrogen Bromide

Hydrogen is abundant in nature but occurs primarily in stable compounds that require significant energy to produce hydrogen for use as a fuel. Therefore hydrogen is an energy carrier, much like electricity, that requires a primary energy source to produce. Domestic energy sources that do not generate greenhouse gases and have the potential to produce hydrogen at costs competitive with carbon based fuels will be essential components of the long term energy supply. Thermochemical cycles which produce hydrogen through a series of chemical reactions have the potential to produce pure hydrogen at high efficiencies. Two promising cycles which are of interest are based on the internal recycle of sulfuric acid and bromine. We present here an electrochemical process that produces pure hydrogen and recycles sulfuric acid and bromine via the electrochemical oxidation of SO₂ and HBr, respectively in the gas phase. Both of these electrochemical reactions take place in a proton exchange membrane (PEM) reactor, similar in construction to a PEM fuel cell. The reactants, either SO₂ or HBr, are fed to the anode and water is fed to cathode. Protons are formed at the anode, and transported across a Nafion membrane, which are then reduced at the cathode to form hydrogen. The performance of the reactor is studied at the optimal conditions of operation for the PEM reactor. The process details for the SO₂ oxidation are reported and it can be shown that there are two distinct reactions occurring during the electrolysis in both higher and lower current densities.