(583b) Direct Characterisation of Gas Adsorption with Raman Spectroscopy

Characterising the sorption properties of materials is necessary for many industrial applications, as well as the development of novel materials with improved capacity and advanced functionality. However, depending on the characterisation technique, measurements are typically limited by a combination of relatively long acquisition time, pressure range, and required sample size. To overcome such constraints, we demonstrate a direct characterisation of gas adsorption using high-resolution Raman spectroscopy. Raman spectroscopy allows the physical and chemical features of optically compatible materials to be directly investigated by detecting vibrational modes that identify the composition and phase of the constituent molecules. In conjunction with a custom built high-pressure, temperature controlled visual cell, this approach enables absolute adsorption capacity to be rapidly measured over a wide range of temperature and pressure. In this work, we validate this novel technique by reporting results for the CO₂ adsorption capacity of a commercial silica gel, measured at 30 °C and at pressures up to 3 MPa. The results from Raman spectroscopy are compared to independent measurements using commercial gravimetric sorption and physisorption apparatuses at high and low pressures respectively, with good agreement over the entire pressure range within the combined uncertainties of each technique. Work is currently underway to extend the functionality of this technique to include adsorption selectivity. Moreover, Raman imaging opens the possibility for heterogeneous adsorption to be spatially resolved and studied within individual particles.