CO2 capture and H2 production performance of calcium-based sorbent doped with iron and cerium during calcium looping cycle

As the interest in environmentally-friendly energy processes increases, many studies have been focused on producing hydrogen as an alternative energy carrier via catalytic reaction processes. Sorption enhanced water gas shift (SEWGS) that combines WGS and in situ CO2 removal is a promising technology for high-purity H2 production and CO2 capture. In this study, Fe/Ce-modified CaO-Ca12Al14O33 bi-functional porous nanotubes were synthesized in one step by template method and applied for H2 production from SEWGS process. The unique porous nanotube structure fully exposes the catalytic active sites and facilitates the gas-solid transport, resulting in the excellent H2 production and CO2 capture performance in SEWGS/regeneration cycles. The introduction of Ce enhances the basicity of the nanotube material, thereby increasing the affinity for CO2. The interaction of Fe-Ce improves the redox capability of Fe2+ and Fe3+, which is beneficial to the conversion of CO. In addition, the formed Ca2Fe2O5 and Ca2CeO4 both increase the concentration of oxygen vacancies, further enhancing the SEWGS reactivity of the material. The optimal molar ratio of Fe/Ce/Al/Ca is 10/3/10/100, and the CO conversion, H2 concentration, CO2 capture capacity of the Fe/Ce-modified bi-functional material were 76.9 %, 70.1 % and 83.2 % after 20 cycles. The effect of Fe/Ce doping on CaO-based materials was investigated at the molecular level using density functional theory (DFT). The results demonstrate that the addition of Ce can effectively maintain the stable structure of Fe-CaO-based materials. The modification of Fe/Ce is expected to promote efficient H2 generation from CaO-based materials through the SEWGS process.