Hydrofluoroolefins (HFOs) are the most important 4th generation refrigerants and are hydrofluorocarbons (HFCs i.e. the banned 3rd generation) that incorporate a carbon-carbon double bond, increasing their reactivity in the troposphere.1. They have short atmospheric lifetimes, zero ozone depletion potential and are currently classified to have global warming potentials (GWPs) of approximately 1 (determined by their contribution to surface heating over a century relative, by mass, to CO2) but concerns are mounting on their decomposition to persistent species such as trifluoracetic acid (TFA)2.
Their atmospheric decomposition is often not fully characterised and mostly inferred from the known chemistry of analogous compounds, end-product analysis, as well as computational chemistry predictions. Further, the majority of studies focus on their decomposition in polluted regions, which is less important in low NOx environments such as Europe and Australia, as well as rural and regional locations. Furthermore, atmospheric NOx concentrations are decreasing globally3. due to environmental regulations (NOx is a toxic pollutant in its own right), so this type of chemistry will continue to become more important elsewhere. Unlike NOx conditions, HO2 chemistry is expected to produce a wide array of products,4. However this has not been studied for this family of compounds, which underpins the need for their study before widespread adoption.
This presentation will present recently acquired data from the MPIMS endstation on the Chemical Transformations, Vacuum Ultraviolet beamline (9.0.2) at the Advanced Light Source synchrotron, Lawrence Berkeley National Laboratory focusing specifically on the decomposition of these compounds in low NOx environments where HO2 chemistry becomes more important. Experimental data and preliminary analysis on the identities of reaction products and intermediates, as well as the kinetics of their formation compared to the known NOx chemistry will be discussed.