Chemical absorption of CO2: Investigations on molecular structure-activity relationships for primary and secondary amine solutions.
10:30 - 11:30
Dr. Ronny Golnak
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Department of Highly Sensitive X-Ray Spectroscopy (FG-AHSX)
We applied a combination of resonant inelastic
X-ray scattering (RIXS) and resonant photoelectron spectroscopy (RPES)
measurements to different amine-solutions before and after CO2 uptake. These
core level spectroscopies are highly sensitive to the effects of hydrogen bonding
interactions with solute species as well as charge transfer in liquid solutions.
By probing the N, O and C K-edge we were able to determine the energy gaps
between the lowest unoccupied molecular orbital (LUMO) and the highest occupied
molecular orbital (HOMO). The HOMO-LUMO gap is of large interest because it serves
as an indicator of molecular properties, such as stability and reactivity, as
well as the chemical environment of the dissolved molecules. By acquiring the N
1s and C 1s XPS spectra of the solutions, the binding energies of 1s core
levels were obtained. The differences of the local chemical environment around
N sites make it possible to distinguish amine from amine-H+ in water in the XPS
spectra, while the carbamate and carbamic acid species are clearly observable
by their different C 1s binding energies. It is also possible to determine the
relative concentration of the species from the measured photoelectron signal
intensities. Moreover, the pKa values could be determined for the carbamic acid
Everyone is warmly welcome to attend.