Low-temperature chemical looping steam methane reforming process using facet-controlled nano CeO2 carbon carrier

• Low-temperature methane steam reforming enabled via chemical looping. • 001 facet-exposed CeO 2 nanocubes serve as carbon carriers to enhance hydrogen production. • Hydrogen is selectively produced during methane flow, with carbon removed during steam flow. • Oxygen vacancies govern the overall pathway, driving sustained hydrogen generation. Conventional steam methane reforming (SMR) requires high temperatures (>800 °C) and suffers from carbon deposition, reducing efficiency and deactivating catalysts. To overcome these challenges, we propose a low-temperature Chemical Looping Steam Methane Reforming (CL-SMR) process using 001-facet-exposed cubic CeO 2 (c-CeO 2) as a carbon carrier. Unlike conventional looping systems, this process enables direct hydrogen generation during methane conversion via active oxygen vacancies. c-CeO 2, with a high oxygen vacancy density (2. 26 × 10 2 µmol·g −1 at 500 °C), promotes methane activation and facilitates effective regeneration of oxygen vacancies while enabling carbon oxidation during the steam step. Cyclic CH 4 –H 2 O reactions at 500 °C under isothermal conditions yielded stable hydrogen production (∼30 µmol·g −1) after the initial cycles, and kinetic analysis indicated that the desorption and oxidation of carbon species coupled with vacancy regeneration constitutes the rate-determining step. This CL-SMR approach demonstrates the potential for efficient low-temperature hydrogen production using c-CeO 2 as a carbon carrier, providing a promising route toward energy-efficient and environmentally sustainable reforming technologies.