## 1 Introduction  
As the global economy and society continue to develop, energy consumption is steadily increasing. The Energy Institute (EI), in its _Statistical Review of World Energy_[1], reported that 2023 was marked by global energy shortages, with primary energy consumption rising by 2% compared to 2022. Renewable energy accounted for over 18% of total consumption, while the share of fossil fuels declined by 0.4%. Although the global energy transition remains gradual, different regions are adopting diverse approaches to energy transformation. Hydrogen, recognized as a clean and efficient energy carrier, has garnered significant attention worldwide. In October 2024, the International Energy Agency (IEA) released the 2024 Global Hydrogen Review [2], which indicated that global hydrogen demand reached 97 million tons in 2023, reflecting a 2.5% year-on-year increase. Despite planned projects aiming to produce up to 49 million tons of green hydrogen annually by 2030, supply is projected to fall short of demand. Consequently, the development of efficient, clean, and scaled-up hydrogen production technologies has become a research priority. Among various hydrogen production methods, the thermochemical iodine-sulfur (I-S) cycle, initially proposed by General Atomics (GA) [3, 4, 5], is regarded as one of the most promising technologies due to its industrial scalability and compatibility with diverse energy sources such as solar, nuclear, and industrial waste heat [6; 7]. The I-S cycle comprises three key reactions:  
\[\text{The Bunsen reaction}:2\text{H}_{2}\text{O}+\text{I}_{2}+\text{SO}_{2} \overset{290-390\text{ K}}{\rightarrow}\text{H}_{2}\text{SO}_{4}+2\text{HI} \tag{1}\]  
\[\text{The HI decomposition reaction}:2\text{HI}\overset{570-770\text{ K}}{\rightarrow}\text{H}_{2}+\text{I}_{2} \tag{2}\]  
\[\text{The H}_{2}\text{SO}_{4}\text{ decomposition reaction}:\text{H}_{2}\text{SO}_{4} \overset{970-1270\text{ K}}{\rightarrow}\text{H}_{2}\text{O}+\text{SO}_{2}+1/2 \text{O}_{2} \tag{3}\]  
In recent years, significant progress has been made in fundamental research on the three aforementioned reactions. However, challenges remain, including severe corrosion conditions, the high temperature required for sulfuric acid decomposition, and the continuous transport and circulation of gases and liquids. While researchers from various countries have made efforts to improve system construction and continuous operation, they continue to encounter difficulties in the practical application of the technology. As the originator of the iodine-sulfur cycle process, General Atomics (GA) designed and built the world's first thermochemical iodine-sulfur cycle hydrogen production system. The theoretical hydrogen production rate of the system was 4 L/min, with a thermal efficiency of 47% [8]. However, due to various issues, the actual hydrogen production rate during intermittent operation was only 20 mL/min. Subsequently, with support from the U.S. Department of Energy's Nuclear Energy Office and in collaboration with Sandia National Laboratories (SNL) and the French Commissariat a l'Energie Atomique (CEA), GA undertook an International Nuclear Energy Research Initiative (INER) [9] to explore the feasibility of using the iodine-sulfur cycle for hydrogen production with nuclear energy. The system, constructed from glass-lined steel and tantalum-tungsten alloy, ultimately achieved continuous operation for 18 h, with hydrogen production rates ranging from 10 to 75 L/h. The Italian National Agency for New Technologies, Energy, and Sustainable Economic Development (ENEA) designed and successfully operated a 10 L/h iodine-sulfur hydrogen production system constructed from glass and polytetrafluoroethylene (PTFE), achieving 48 h of operation [10; 11]. The Japan Atomic Energy Agency (JAEA) successfully operated a 1 L/h hydrogen production system made of glass for 48 h in 1997, confirming the feasibility of the iodine-sulfur hydrogen production method [12].