Thermal stability and decomposition of two gelled electrolyte systems, designed for alternative Grätzel-type solar cells, based on a short or a long chain bisUreaSil gel with or without an electrolyte (LiI/I2/MPII, MPII = 1-methyl-3-propylimidazolium iodide), have been followed by thermogravimetric analyzers coupled with quadrupole mass spectrometer (MS) or FTIR spectroscopic gas cell. These evolved gas analytical tools allow us to make comparisons on thermally accelerated processes of solvents’ vaporization, gels’ degradation and electrolytes’ decomposition. The solvents, acetic acid and sulfolane are retarded at room temperature, but released gradually at higher temperature. Above 300 °C, an oxidative thermal degradation is indicated by formaldehyde and carbon monoxide, or dinitrogen-oxide and ammonia, for long- and short-chain gel samples (S4000 and S230), respectively. The inclusion of iodic electrolyte components (LiI/I2/MPII) into the gels seems to lower the degradation temperature of the gels’ framework significantly, meanwhile evolution of various alkyl iodides could also be detected by EGA-MS. Thermal decomposition of pure ionic liquid, MPII alone and also in fully assembled samples have also been studied in details. Several gaseous decomposition products were observed, and possible degradation pathways are established.
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry