Insights into sulfur resistance of Ce-doped CaO in sorption-enhanced steam gasification: A combined DFT and experimental study

The sorption-enhanced steam gasification of biomass using CaO-based materials is considered a promising method for H 2 production, while the presence of H 2 S in the syngas results sulfur poisoning of the materials. In this work, DFT calculations were combined with experimental verification to elucidate the mechanism of H 2 S resistance and structural stability of Ce-doped CaO material. The theoretical results reveal that Ce-doping significantly modulates the surface electronic structure, and Ce-doped CaO surface exhibits less negative H 2 S adsorption energies and higher activation barriers for the initial dissociation steps compared with pristine CaO, thus the onset of the sulfidation reaction is inhibited. Furthermore, the formation of oxygen vacancies is energetically less favorable on Ce-doped CaO surfaces, which is a prerequisite for sulfidation reaction. Even under sulfur-poisoning conditions, the Ce-doped CaO retains superior CO 2 adsorption, and the adsorption of Ca 4 O 4 clusters demonstrates that a robust chemical anchoring effect was introduced by Ce-doping. Experimental results from 20 cycles of steam gasification of high‑sulfur Enteromorpha prolifera validate these theoretical findings, and Ce-doped CaO maintains high H 2 production and CO 2 capture performances with minimal sulfur-poisoning deactivation.