Two-step thermochemical cycle for solar fuel production from H₂O and CO₂: technological challenges and potential solutions

A two-step thermochemical cycle for solar fuel production technology is considered a promising path for alternative energy of fossil fuels, because it employs solar energy as a high-temperature heat supply to directly convert H₂O or/and CO₂ into H₂ or/and CO, which is well in line with the requirements of carbon neutrality. A large amount of effort has been put into this research, but there are still several bottleneck issues that need to be addressed. In this review, we present the working principles of a two-step thermochemical cycle for solar fuel production and discuss the current technological challenges hindering such technology's further development towards large-scale application, such as severe operating conditions and low solar-to-fuel efficiency. Finally, we explore the potential solutions from the perspectives of materials and reactors based on current status and demand, which can serve as guidance for future innovations in this field.