(569ad) Synergistic Approach for Enhanced Hydrogen Generation from Hydrogen Sulfide Using Nanoparticles for Sulfur Looping: Reactivity Improvement By Structural Tuning.

With the increase in global energy demand, it is estimated that more than 50% of this demand will still be dependent on fossil-based energy sources by 2050. Hydrogen sulfide (H₂S) encountered in fossil fuels is currently treated using the state-of-the-art Claus process that faces limitations such as high energy requirements, poor energy efficiencies, and loss of H content from H₂S in the form of low-value steam. Sulfur looping presents a viable two-step thermochemical alternative to convert H₂S to hydrogen (H₂) and elemental sulfur using an intermediate sulfur carrier. Iron sulfide (FeS) has been widely studied as the carrier material, but the poor kinetics significantly limit the H₂S conversions. In this work, we aim to enhance the reactivity of iron-based sulfide carriers by developing nano-sized Fe₉S₁₀ carrier for the nanoparticle enhanced sulfur looping (NE-SL) scheme. Extended testing of nano-sized redox carrier in a thermogravimetric analyzer shows a stable reactivity with an improvement in sulfur uptake over bulk-sized carriers by ~69%. Additionally, co-feed experiments in the presence of CO₂ were conducted to test the robustness of the nano-sized carriers. The results indicate a similar performance with no impurity phase formation in the solid carrier. Solid characterization techniques such as temperature programmed sulfidation, N₂ physisorption, X-ray diffraction, and transmission electron microscopy were used to support and validate the observed reactivity enhancement. Atomistic level density functional theory calculations were performed to understand the reaction mechanism of the sulfur looping process using nano-sized carriers. Finally, a detailed process analysis of the NE-SL scheme indicates an energy and exergy efficiency improvement of 22 and 7.71 percentage points, respectively, over the Claus process. Therefore, this work provides valuable insights into the design of the sulfur carriers for the sulfur looping process and establishes the thermodynamic superiority of the NE-SL scheme over the state-of-the-art Claus process.