Core-shell iron-based oxygen carrier material for highly efficient green hydrogen production by chemical looping

The provision of green hydrogen on an industrial scale is one of the challenges for a successful CO₂-neutral energy transition. Sintering is still the bottleneck for the use of iron-based oxygen carriers for efficient hydrogen production and storing performance in chemical looping in a large-scale system. In this work, we demonstrate an effective way for hydrogen production by the synthesis of structured oxygen carriers (OC) from cost efficient, green and environment-friendly materials. The novel structured oxygen carriers with a core–shell architecture show an innovative concept to prevent the agglomeration of pellets in the fixed bed reactor system. The environment-friendly iron-based material maintained an oxygen exchange capacity of over 80 % for 100 cycles. The pore network of the catalytic system was preserved by incorporating a structure with separate compartments. A synergistic effect between the sintering, especially of the porous network, and the gas transport was revealed. In addition, an undiscovered leach-out effect of the OC system on the Al₂O₃ support material, which is associated with a deactivation phenomenon, was also revealed. The work provides fundamental new insights for understanding the phenomena that occur during the sintering process in the OC material and the influence on the lifetime of the chemical looping process. Finally, we present that the structured OC exhibits excellent performance and provides a new approach in material design for successful implementation in high temperature catalytic fixed bed system for long term operation.