Infrared investigation of CO2 sorption by amine based materials for the development of a NDIR CO2 sensor

We present a new CO2 IR sensor concept for indoor air quality (IAQ) combining infrared detection and CO2 sorbent material. Different CO2 sorbent materials were screened and polyethyleneimine cross-linked with glutaraldehyde shows the best sorption performance. CO2 sorption into/desorption from PEI layers was monitored at different CO2 concentrations, temperatures and humidities by in-situ transmission infrared spectroscopy. It was found that the CO2 adsorption takes place in two steps: a fast adsorption at the upper surfaces followed by the slow diffusion of the chemisorbed CO2 in the bulk. The adsorption depends on the CO2 concentration in the gas phase during the first 10 min. 50 °C is found to be the optimum adsorption temperature in the case of thick (mm scale) PEI layers. An increase in humidity results in enhanced CO2 sorption. CO2 desorption requires inert gas flow and long exposure times at room temperature. As temperature increases, thermal desorption is prevalent at 70 °C and is faster at 100 °C.