Pt-Ce_0.9 Cu_0.1 O₂ /activated carbon as highly active and stable HI decomposition catalyst

Abstract

Summary Effects of additives to Pt‐CeO2/activated carbon (M563) catalysts on HI decomposition were studied. Among the additives studied, it was found that the addition of Cu to Pt‐CeO2 is the most effective for increasing the catalytic activity to HI decomposition. On this catalyst, almost the equilibrium hydrogen iodide (HI) conversion was achieved at temperature higher than 573 K. Cu addition increased Pt dispersion by anchoring effects. Therefore, in spite of decreased Brunauer‐Emmett‐Teller surface area of the catalyst, dispersion of Pt was much increased by addition of Cu resulting in the increased HI decomposition activity and stability. Because formed I2 adsorbed on the catalyst at initial ca 20 hours, HI conversion was higher than that of the equilibrium one; however, after 20 hours, stable HI decomposition conversion that was almost the same with equilibrium conversion was achieved in the examined temperature range.

Pt-Rh/TiO2 /activated carbon as highly active and stable HI decomposition catalyst for hydrogen production in sulfur-iodine (SI) process

“…It is reported that the coexistence of water shows negative effects on HI decomposition and so HI decomposition on Pt‐Rh/TiO 2 /M563 catalyst was measured under coexistence of H 2 O. Figure shows temperature dependence of HI conversion under dry and coexistence of H 2 O (25 vol%).…”

“…Advantage of metal oxide‐supported Pt is high stability; however, the activity is still not high enough. In our previous study, we found that Pt/Ce(Cu)O 2 /activated carbon is highly active to HI decomposition (almost the equilibrium conversion) as well as high stability over 100 hours . However, from the equilibrium, CeO 2 has reactivity with I 2 resulting in a decreased HI conversion.…”

Modeling and experimental assessment of the novel HI‐I 2 ‐H 2 O electrolysis for hydrogen generation in the sulfur‐iodine cycle

“…The influence of operating temperature on the electrolytic performance was analyzed in two opposite aspects. First, increase in temperature enhances the activity of species in the solution and increases the reaction kinetic rate because of the endothermic characteristic of HI decomposition . On contrary, the rising temperature reduces the local current density according to Equation .…”

“…And excess H 2 O is also necessary for making the Bunsen reaction more thermodynamically favorable . As a result, the practical excess amounts of I 2 and H 2 O with respect to their stoichiometric value usually reach 4 to 6 and 11 to 13 according to Lee et al The produced light H 2 SO 4 phase (most H 2 SO 4 , H 2 O and less HI, I 2 ) and the heavy HIx phase (most HI, I 2 , H 2 O and less H 2 SO 4 ) require liquid phase separation and purification before the catalytic decomposition of H 2 SO 4 and HI . A large amount of energy is required to remove and recycle the excess iodine and water after liquid phase separation.…”

“…19 As a result, the practical excess amounts of I 2 and H 2 O with respect to their stoichiometric value usually reach 4 to 6 and 11 to 13 according to Lee et al 17 The produced light H 2 SO 4 phase (most H 2 SO 4 , H 2 O and less HI, I 2 ) and the heavy HIx phase (most HI, I 2 , H 2 O and less H 2 SO 4 ) require liquid phase separation 16 and purification [20][21][22] before the catalytic decomposition of H 2 SO 4 and HI. [23][24][25][26] A large amount of energy is required to remove and recycle the excess iodine and water after liquid phase separation. Wang and coworkers 27 has proposed the electrolysis of the HI/H 2 SO 4 /H 2 O/toluene mixture from Bunsen reaction so as to avoid the liquid phase separation.…”