Development of catalysts for hydrogen production from hydrogen iodide decomposition in thermo-chemical water-splitting sulfur-iodine cycle: A review

Hydrogen iodide (HI) decomposition is an important part of thermo-chemical water-splitting sulfur-iodine (SI) cycle which can generate large amount of hydrogen without releasing green-house carbon dioxide gas. HI-decomposition is a very slow reaction even at a high temperature of 500 degrees C. The use of catalyst in this reaction increases the reaction rate. So, a highly active and stable catalyst is desired from long time. Development of active and stable non-noble catalysts for HI-decomposition reaction is a significant challenge. Recent developments and trends in catalysis towards the catalyst synthesis, activity, and stability are discussed in this review. The activity, stability, and kinetic studies of different support materials, different monometallic and bimetallic catalysts are summarized here. The effect of preparation methods of catalysts on their activity and stability is also discussed. The high activity of catalysts for HI reaction is related to nanosize particles, metal dispersion, high specific surface area, oxygen vacancies (defects), and alloy formation between two metals. This article also summarized the different material of construction (MoC) used for HI reaction which are essential for building big pilot plants.