Experimental and kinetic studies of the electrochemical Bunsen reaction in the sulfur-iodine cycle for hydrogen production

摘要

To reduce the excess of iodine and water in the Bunsen reaction of sulfur-iodine cycle, application of an electrochemical cell to Bunsen reaction has been proposed. The cell consists of two electrodes and two compartments separated by a proton exchange membrane, SO_2 is oxidized to H_2SO_4 at anode while I_2 is reduced to HI at cathode. Concentration of H_2SO_4 and HI solutions and electric energy consumption were determined using Nafion 115 and 117. Apart from the desired proton transferring from anolyte to catholyte, other unexpected solutes can pass through membrane. So the cross-contamination between two solutions was measured. Both electrodes were electrochemically characterized using cyclic voltammetry and electrochemical impedance spectroscopy, and electrode reaction kinetics was analyzed. Results showed that each of membrane was more favorable at some conditions. The concentration of contaminants in anolyte was 2-10 times higher than that in catholyte using Nafion 115. A high electrode reaction rate was obtained for HI of 8 mol/kg_(H2O), I_2/HI molar ratio of 0.5, and H_2SO_4 of 13 mol/kg_(H2O). Compared with the traditional Bunsen reaction, 85-95% of the iodine content in HI solution was reduced, so did 10-50% of the water in H_2SO_4 solution using this method.