Exploring Colloidal Silica Nanoparticles for Carbon Dioxide Capture and Storage

Reducing the emissions of carbon dioxide is critical to prevent climate change. Carbon dioxide Capture and Storage (CCS) provides one step in that direction. Mesoporous materials, such as silica, are studied as sorption materials for CCS to decrease the energy demand of regeneration compared to the more frequently used liquid amines. In the search for the optimal sorption material, the isosteric heat of adsorption, Qst, of CO2 is a key factor to consider. In this project the CO2 adsorption ability of colloidal silica nanoparticles (NP) provided by AkzoNobel PPC AB was measured optically using Indirect Nanoplasmonic Sensing (INPS). INPS relies on Localized Surface Plasmon Resonance (LSPR), which is highly sensitive to the refractive index of the surrounding medium. Thus, it constitutes a suitable tool for detecting gas adsorption on solid surfaces. Specifically, INPS provides an effective way of studying CO2 adsorption without influencing the sample and without calibration. Colloidal silica nanoparticles of two sizes were studied, along with two types of amine functionalizations. A reproducible method for depositing the silica nanoparticles on the INPS sensor surface was developed. It was established that the silica particles indeed adsorb CO2, and a larger LSPR response was obtained for the smaller particles due to their larger specific surface area. The estimated isosteric heat of adsorption agreed well with literature. The average value for bare silica par- ticles was 19.9 kJ/mol and for amine functionalized NPs the average isosteric heat was slightly lower, namely 14.6 kJ/mol.