Accelerating carbon mineralization and hydrogen generation in peridotite via CO2 nanobubbles

CO2 mineralization is currently the safest permanent carbon sequestration solution. However, under natural geological conditions, CO2 mineralization occurs at an extremely low rate, typically taking hundreds or even millions of years. Herein, CO2 nanobubbles are employed as a new possible alternative to accelerate carbon mineralization and simultaneously generate hydrogen in peridotite, and the acceleration mechanisms of CO2 nanobubbles are brought to light. The findings indicate that CO2 nanobubbles enhance the supersaturation of CO2 in the aqueous phase and promote the dissolution of peridotite particles. Mineralogical and spectroscopic analyses further confirmed accelerated silicate dissolution and carbonate precipitation in the nanobubble system. Notably, CO2 nanobubbles increase the macropore proportion by approximately 28% and enhance the product layer diffusion coefficient from 1.08×10-16 m2·s-1 to 11.89×10-16 m2·s-1. The ultimate mineralization degree and hydrogen yield of the CO2 nanobubble system are approximately 2.08-fold and 1.45-fold that of the carbonated water system, respectively, corresponding to an additional 53.7 kg of CO2 sequestered and 2.34 g of H2 generated per tonne of peridotite. Furthermore, the generation of H2 is related to changes in the interfacial water structure and the oxidation of Fe(II), in which Fe(II) may act as an electron donor for proton reduction. This research provides a pathway for efficient CO2 sequestration and hydrogen generation, which provides theoretical assistance for CO2 geological sequestration and energy transition.