Hydrofluoroolefins (HFOs) are a new generation of refrigerants designed as environmentally friendly replacements for older halocarbons. They have very low global warming potential and zero ozone depletion potential, leading to their rapid adoption in commercial and domestic systems, such as automotive air conditioning and heat pumps. Global emissions of HFOs are projected to exceed one million tonnes annually by 2050, primarily in densely populated regions. Despite their growing use, the atmospheric breakdown of HFOs is poorly understood. Once released, they are oxidised to form potentially hazardous products such as carbonyls, secondary organic aerosols (SOA), and trifluoroacetic acid (TFA), a persistent “forever” chemical with implications for air quality, health, and climate.
A particularly important but underexplored process is the ozonolysis of HFOs, especially at night when photochemical oxidants like OH are absent. Ozonolysis of alkenes generates highly reactive Criegee intermediates (CIs), which are now known to be key drivers of radical and particle formation in the atmosphere. However, the chemistry of fluorinated Criegee intermediates (HFO-CIs) has scarcely been studied. Their potential to form toxic oxidation products, drive SOA growth, and influence tropospheric oxidative capacity represents a major knowledge gap.
This studentship will focus on fundamental laboratory and computational studies of HFO-CIs, providing the first direct spectroscopic detection of their structures, reaction rates, and branching ratios with common atmospheric species. Experiments will be conducted using cutting-edge laser techniques uniquely capable of selective detection of trace reactive intermediates. In parallel, high-level quantum chemical calculations and master-equation modelling will characterise the reaction pathways and provide insights into conformer-specific reactivity.
The results will be incorporated into the Master Chemical Mechanism (MCM), the international benchmark for atmospheric modelling, and applied in urban air quality scenarios (e.g. Beijing, Delhi) to assess the wider impacts of HFO chemistry on oxidative budgets, ozone formation, and aerosol production. This interdisciplinary project bridges laboratory spectroscopy, computational chemistry, and atmospheric modelling, offering the student a unique opportunity to contribute to a pressing environmental challenge at the interface of physical chemistry, climate science, and public health.
This project is not suitable for CASE funding
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The student will develop expertise in advanced spectroscopic techniques to study the ozonolysis products of hydrofluoroolefins. Laboratory work will centre on laser spectroscopy, applied to a custom-built flow reactor, to directly detect fluorinated Criegee intermediates and their reaction products. Experiments will quantify pressure- and temperature-dependent rate coefficients and product branching ratios for reactions with key atmospheric species (H₂O, SO₂, NO₂, organic acids). The student will also investigate the formation of secondary organic aerosol precursors under extended reaction conditions.
Complementing the experiments, the student will perform high-level ab initio quantum chemical calculations and master-equation modelling (using MESMER) to map reaction potential energy surfaces, derive k(T,p) values, and generate predicted infrared spectra for molecular identification. These combined datasets will be incorporated into detailed atmospheric chemical models, including the Master Chemical Mechanism (MCM), Py-CHAM and AtChem, to evaluate the impacts of HFO degradation on urban air quality, radical chemistry, and SOA formation under realistic emission scenarios.
DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.
The student will receive comprehensive training in both experimental and computational aspects of atmospheric chemistry. Technical skills will include advanced spectroscopic methods (laser / cavity-enhanced techniques), flow reactor design, trace intermediate detection, and quantum chemical and master equation calculations. You will also become proficient in programming (e.g. Python) and established atmospheric chemistry modelling tools. Alongside lab and theoretical training, you will develop transferable skills in scientific writing, presenting at conferences, collaborating across multidisciplinary teams, data analysis and project management. Opportunities for workshops, seminars, and co‐supervised work will further support your professional development and readiness for both academic and non‐academic careers.
Not applicable.
Year 1: Laboratory instrument final development and construction (furthering pre-existing instrumentation). Building a computational chemistry framework. Preliminary data collection of HFO-sCI reaction rate coefficients.
Year 2: Generation of a breadth of HFO-sCI rate coefficients. Classification of these coefficients for inclusion into Master Chemical Mechanism and AtChem models for the atmosphere. Evaluation of site-localised impact of rate coefficients. First studies of products, identified through UV/IR spectroscopy.
Year 3: Finalising a body of rate coefficients, and complementary values generated through ab initio computational chemistry. Inclusion of rate coefficients and ideally branching fractions into atmospheric models.
Journal:
Holland, R., Khan, M. A. H., Driscoll, I., Chhantyal-Pun, R., Derwent, R. G., Taatjes, C. A., Orr-Ewing, A. J., Percival, C. J. & Shallcross, D. E. (2021) Investigation of the Production of Trifluoroacetic Acid from Two Halocarbons, HFC-134a and HFO-1234yf and Its Fates Using a Global Three-Dimensional Chemical Transport Model. ACS Earth and Space Chemistry, 5, 849-857. Doi: 10.1021/acsearthspacechem.0c00355
Andreae, M. O. (2013). The Aerosol Nucleation Puzzle. Science, 339, 911-912. Doi:10.1126/science.1233798
Watson, N. A. I. & Beames, J. M. (2023). Bimolecular sinks of Criegee intermediates derived from hydrofluoroolefins – a computational analysis. Environmental Science: Atmospheres, 3, 1460-1484. Doi: 10.1039/D3EA00102D
For any enquiries related to this project please contact:
Dr Joseph M. Beames
Associate Professor of Physical Chemistry,
School of Chemistry,
University of Birmingham.
[email protected]
To apply to this project:
Applications must be submitted by 23:59 GMT on Wednesday 7th January 2026.