Oxygen Carriers for Chemical-looping Water Splitting to Hydrogen Production: A Critical Review

Chemical looping water splitting (CLWS) process using metal oxides or perovskites as oxygen carriers (OCs), is capable of producing pure H2 in an efficient, simple, and flexible way. The OCs are first reduced by hydrocarbon fuels and then oxidized by steam in a cyclic way. After the condensation of the gaseous mixture of steam and H2 from the oxidation step, pure H2 is obtained. In recent years, great efforts for CLWS have been made to improve the redox activity and stability of OCs. In this paper, the development of the OCs for hydrogen production from CLWS were discussed. Effects of supports and additives on the performances of OCs were compared based on redox reactions in CLWS. Fe-based OCs with CeO2, Al2O3, ZrO2, CuO, MoO3, Rh etc. are very attractive for the CLWS process. Issues and challenges for the development of OCs were analyzed.