Oxygen Vacancy Enhanced Proton Transfer to Boost Carbamate Decomposition Kinetics with Tunable Heterostructure Ni/NiO

Catalytic carbamate decomposition is a feasible option for reducing the heat duty of amine solvent regeneration during the chemisorption of CO2 capture; advanced material with excellent proton transfer and exchange performance is crucial to boost the decomposition kinetics in an alkaline environment. Here, we prepared magnetic heterostructure Ni/NiO nanocatalysts with tunable Ni(0) nanoparticles and NiO support. The heterointerface of the proposed materials creates abundant surface oxygen vacancies (OVs) and offers abundant reactive active sites ascribed to the special electron transfer scheme of Ni-0-NiO. The generated surface hydroxyls and unsaturated coordinated Ni, respectively, provide transferable protons and electrons, involved in the deprotonation of RNH3+ and C-N break of RNHCOO-. Thus, the obtained nanomaterials achieved considerably improved CO2 desorption of up to 3 mmol/min for a CO2-saturated monoethanolamine solvent, representing a substantial (approximately 50%) increase over the catalyst-free case. The reinforcement mechanism of OV generation by the Ni/NiO heterostructure and the induced proton transfer were revealed through in situ spectroscopic measurement and theoretical calculations. The results verified that the OVs stimulate the production of surface hydroxyls and water-assisted proton hopping, providing an advantageous condition for carbamate decomposition.