High-throughput design of complex oxides as isothermal, redox-activated CO2 sorbents for green hydrogen generation†

Sorption-enhanced reforming and gasification (SERG) offers a promising approach to intensify hydrogen production from carbonaceous feedstocks. However, conventional sorbents require substantial temperature increases for the endothermic CO₂ release step and are prone to deactivation. This study introduces a new class of redox-activated sorbents capable of stable isothermal operation and tunable heats of reactions, thereby facilitating an efficient reactive separation scheme. Using plane-wave density functional theory (DFT) calculations of structures and free energies, we screened 1225 perovskite-structured sorbent candidates, followed with extensive experimental validation. An effective descriptor, (ΔG_abs + ΔG_reg), was identified to expedite sorbent optimization. The advanced sorbents showed reversible, isothermal carbonation of up to 78% of the A-site cation, permitting isothermal SERG or “iSERG”. Their versatility was demonstrated in a fluidized bed for woody biomass gasification and a packed bed for biogas conversion, yielding hydrogen-enriched (73 vol%) syngas from biomass and 95+% pure H₂ from biogas. Our results also support integrated CO₂ capture to produce carbon-negative hydrogen products.