Low Temperature Synthesized H2Ti3O7 Nanotubes with a High CO2 Adsorption Property by Amine Modification.

Carbon dioxide (CO2) capture and storage (CCS) technologies have been attracting attention in terms of tackling with global warming. To date, various CO2 capture technologies including solvents, membranes, cryogenics, and solid adsorbents have been proposed. Currently, a liquid adsorption method for CO2 using amine solution (monoethanolamine) has been practically used. However, this liquid phase CO2 adsorption process requires heat regeneration, and it can cause many problems such as corrosion of equipment and degradation of the solution. Meanwhile, solid adsorption methods using porous materials are more advantageous over the liquid method at these points. In this context, we here evaluated if hydrogen titanate (H2Ti3O7) nanotubes and the surface modification effectively capture CO2. For this aim, we first developed a facile synthesis method of H2Ti3O7 nanotubes different from any conventional methods. Briefly, they were converted from the precursors-amorphous TiO2 nanoparticles at room temperature (25 °C). We then determined the outer and the inner diameters of the H2Ti3O7 nanotubes as 3.0 and 0.7 nm, respectively. It revealed that both values were much smaller than the reported ones; thus the specific surface area showed the highest value (735 m2/g). Next, the outer surface of H2Ti3O7 nanotubes was modified using ethylenediamine to examine if CO2 adsorption capacity increases. The ethylendiamine-modified H2Ti3O7 nanotubes showed a higher CO2 adsorption capacity (50 cm3/g at 0 °C, 100 kPa). We finally concluded that the higher CO2 adsorption capacity could be explained, not only by the high specific surface area of the nanotubes but also by tripartite hydrogen bonding interactions among amines, CO2, and OH groups on the surface of H2Ti3O7.