Optimization of the process parameters of an electrochemical cell in the IS process

One of the key reactions for efficient hydrogen production using the water-splitting iodine–sulfur (IS or S–I) process is the Bunsen reaction (SO₂+I₂+2H₂O=H₂SO₄+2HI). The Bunsen reaction was examined using an electrochemical cell with a cation exchange membrane as the separator. The optimal molalities of anolyte and catholyte were evaluated by total thermal efficiency using the heat/mass balance of the IS process. The I₂/HI ratio had little effect on the required total voltage; the I₂/HI ratio can be reduced to 0.5 without decreasing the total thermal efficiency. On the other hand, HI and H₂SO₄ molality greatly affected the total thermal efficiency. The total thermal efficiency increased with increasing HI molality up to and the maximum thermal efficiency was found at of H₂SO₄. Membrane resistances are very important parameters affecting the efficiency. The total thermal efficiency increased by 3.0% at a current density of the electrochemical cell of by increasing the operating temperature from 313 to 363 K.