LAUSR

This study reveals the efficient catalytic role of Ca-Fe-based oxygen carriers (Ca2Fe2O5) in biomass chemical looping gasification. With oxygen carrier introduction, the CO yield doubled (0.13 Nm3/kg→0.26 Nm3/kg), with 76.10% selectivity. Steam co-feeding further increased the H2 yield from 0.19 Nm3/kg to 0.72 Nm3/kg, significantly elevating the H2/CO ratio to 2.62. Combined with density functional theory (DFT), the micro-mechanism of reduced oxygen carrier surfaces activating CO2/H2O was elucidated. CO2 (adsorption charge −0.952 |e|) and H2O (adsorption charge −0.612 |e|) chemically adsorb at the CaO(111)/Fe(110) interface, where Fe atoms (charges 0.433 |e|, 0.927 |e|) act as electron donors to drive efficient molecule activation. CO2 undergoes single-step splitting (CO2→CO* + O*), with the desorption energy barrier (Ea = 1.09 eV, 105.17 kJ/mol) determining the reaction rate. H2O splits via two-step cleavage (H2O→HO* + H*→2H* + O*), which is rate-limited by the first step (Ea = 0.42 eV, 40.52 kJ/mol). Simultaneously, the reduced oxygen carrier achieves oxidative regeneration through surface O* lattice incorporation. This work atomically reveals the “electron transfer–oxygen transport” synergy at the Ca-Fe bimetallic interface, establishing a theoretical framework for the directional regulation of the syngas composition and the design of high-performance oxygen carriers.