Hydroxyl-assisted proton migration and interfacial electron transfer over Ni(OH)2/NiOOH for low-energy CO2 desorption from phase-change absorbent

Integrating phase-change absorption with catalytic desorption offers a promising strategy for low-energy amine-based CO 2 capture; however, catalytic desorption of the CO 2 -rich phase in phase-change absorbents remains challenging because the highly enriched ionic products hinder product activation, proton transfer, and interfacial mass transport. Herein, a Ni(OH) 2 /NiOOH catalyst with an open layered nanosheet structure, abundant surface hydroxyl groups, and interlayer water was developed and applied to both our previously reported phase-change absorbent and a 30 wt% aqueous MEA system. The catalyst increased the maximum CO 2 desorption rate by 40% in the phase-change system and by 43% in the aqueous MEA system, while reducing the relative heat duty by 32.9% in the phase-change system, demonstrating efficient catalytic desorption performance and good cross-system applicability. Structural and mechanistic analyses reveal that the open nanosheet architecture shortens diffusion pathways and improves active-site accessibility, while surface hydroxyl groups and interlayer water construct a hydrogen-bond network for proton migration. Meanwhile, the Ni 2+ /Ni 3+ interface promotes interfacial electron transfer, enhances carbamate polarization, and weakens the C N bond. These effects synergistically facilitate carbamate decomposition and protonated amine deprotonation, providing new insights into catalyst design for low-energy CO 2 capture.