Thermochemical looping technologies for clean hydrogen production – Current status and recent advances

This review critically analyses various aspects of the most promising thermochemical cycles for clean hydrogen production. While the current hydrogen market heavily relies on fossil-fuel-based platforms, the thermochemical water-splitting systems based on the reduction-oxidation (redox) looping reactions have a significant potential to significantly contribute to the sustainable production of green hydrogen at scale. However, compared to the water electrolysis techniques, the thermochemical cycles suffer from a low technology readiness level (TRL), which retards the commercial implementation of these technologies. This review mainly focuses on identifying the capability of the state-of-the-art thermochemical cycles to deploy large-scale hydrogen production plants and their techno-economic performance. This study also analyzed the potential integration of the hybrid looping systems with the solar and nuclear reactor designs, which are evidenced to be more cost-effective than the electrochemical water-splitting methods, but it excludes fossil-based thermochemical processes, such as gasification, steam methane reforming, and pyrolysis. Further investigation is still required to address the technical issues associated with implementing the hybrid thermochemical cycles in order to bring them to the market for sustainable hydrogen production.