A review on the development of supported non-noble metal catalysts for the endothermic high temperature sulfuric acid decomposition step in the Iodine–Sulfur cycle for hydrogen production

Abstract

The decomposition of sulfuric acid to sulfur dioxide is an important reaction section in both the thermochemical Iodine–Sulfur (IS) cycle and the Hybrid (Hybs) cycle for hydrogen production. This decomposition reaction is a high temperature, highly endothermic reaction whose activation barrier needs to be reduced by a highly active catalyst. The catalysts reported in this reaction are either exorbitantly expensive, synthesized using noble metals, or exhibiting low activity and stability. Hence, the development of non-noble active and stable catalysts in this reaction is a significant challenge. This review comprehensively discusses the recent developments and activity trends of supported non-noble catalysts including their synthesis, activity & stability trends, mechanistic and kinetic aspects. The catalytic activity of nano-catalysts in sulfuric acid decomposition is largely affected by the size of the metal nanoparticles, dispersion, oxygen vacancies, and metal-support interaction. Herein, we report an in-depth theoretical and experimental understanding of the catalytic challenges and solutions that leads to designing a cost-effective, efficient and stable catalyst in this reaction. The role of catalyst support modification for long run stability is also discussed. Further, literature considering reaction kinetics over various catalysts is also reviewed.