Occurrence of the Bunsen side reaction in the sulfur-iodine thermochemical cycle for hydrogen production

This study aimed to establish a closed-cycle operation technology with high thermal efficiency in the thermochemical sulfur-iodine cycle for large-scale hydrogen production. A series of experimental studies were performed to investigate the occurrence of side reactions in both the H₂SO₄ and HI _x phases from the H₂SO₄/HI/I₂/H₂O quaternary system within a constant temperature range of 323–363 K. The effects of iodine content, water content and reaction temperature on the side reactions were evaluated. The results showed that an increase in the reaction temperature promoted the side reactions. However, they were prevented as the iodine or water content increased. The occurrence of side reactions was faster in kinetics and more intense in the H₂SO₄ phase than in the HI _x phase. The sulfur or hydrogen sulfide formation reaction or the reverse Bunsen reaction was validated under certain conditions.