Improvement of the thermochemical water splitting IS process by an electrochemical cell using a cation exchange membrane

摘要

One of the key reactions for efficient hydrogen production through the water splitting IS(Iodine-Sulfur) process is the Bunsen reaction (SO2+I2+2H2O= H2SO4+2HI). The Bunsenreaction was examined by an electrochemical cell featuring a cation exchange membrane asthe separator, using sulfuric acid dissolving sulfur dioxide as the anolyte and hydriodic aciddissolving iodine as the catholyte. In galvanostatic electrolysis, molality of H2SO4 in theanolyte and that of HI in the catholyte were increased up to 17.8 mol kg-H2O -1 and 14.9 molkg-H2O -1 at I2/HI = 1, respectively. These concentrations were far higher than the reportedones that were obtained by the Bunsen reaction carried out in the presence of large amount ofiodine (e.g. I2/HI=4). The optimal concentrations of anolyte and catholyte were discussedby changing only one parameter. I2/HI ratio had little effects on the required total voltagesuggesting that lower I2 concentration is desired for the efficient operation. H2SO4concentration was found to be lower than 16 mol kg-H2O -1 for anolyte. One of the importantparameter that should be corrected was water content of the cation exchange membraneduring the experimental especially for the higher concentrations of anolyte and catholyte.