Addressing the Effectiveness and Molecular Mechanism of the Catalytic CO₂ Hydration in Aqueous Solutions by Nickel Nanoparticles

Abstract

Hydration of carbon dioxide in water solution is the rate limiting step for the CO 2 mineralization process, a process which is at the base of many carbon capture and utilization (CCU) technologies aiming to convert carbon dioxide to added-value products and mitigate climate change. Here, we present a combined experimental and computational study to clarify the effectiveness and molecular mechanism by which nickel nanoparticles, NiNPs, may enhance CO 2 hydration in aqueous solutions. Contrary to previous literature, our kinetic experiments recording changes of pHs, conductivity, and dissolved carbon dioxide in solution reveal a minimal effect of the NiNPs in catalyzing CO 2 hydration. Our atomistic simulations indicate that the Ni metal surface can coordinate only a limited number of water molecules, leaving uncoordinated metal sites for the binding of carbon dioxide or other cations in solution. This deactivates the catalyst and limits the continuous re-formation of a hydroxyl-decorated surface, which was a key chemical step in the previously suggested Ni-catalyzed hydration mechanism of carbon dioxide in aqueous solutions. At our experimental conditions, which expand the investigation of NiNP applicability toward a wider range of scenarios for CCU, NiNPs show a limited catalytic effect on the rate of CO 2 hydration. Our study also highlights the importance of the solvation regime: while Ni surfaces may accelerate carbon dioxide hydration in water restricted environments, it may not be the case in fully hydrated conditions.

The Future of CO2 Geological Sequestration: An Overview of Mineralization in Aqueous and Supercritical States

“…For wet scCO 2 , the water content is a contributing factor to mineralization, despite its small quantity. As water is typically fully dissolved in scCO 2 , the effect of water content on mineralization is often described in terms of water film thickness and relative humidity , This is due to the low volume of water film. This section discusses the importance of water film thickness in relation to ion concentration and transverse diffusion efficiency, and how it affects supersaturation and carbonate precipitation .…”