Transitioning to a hydrogen economy: Kinetic isotope effects of stratospheric monodeuterated hydrogen accumulation

• No studies examine the KIE of replacing H with D in the Cl reservoir.
• KIE results for CH4 oxidation imply decreases in PSC formation.
• Stratospheric HD increases slow the rate at which ClCl acts as a sink for H2.

This paper investigates for the first time the influence of monodeuterated hydrogen on kinetics of seven stratospheric radical reactions in a consistent, unified manner using the same level of quantum chemistry computational theory. We optimize transition-state structures using MP2 perturbation theory within the finite aug-cc-pVTZ, and show that the evolution to a full-scale hydrogen economy results in the atmospheric accumulation of heavy methane and heavy hydrogen, which can lead to a decrease of polar stratospheric clouds on which ozone is depletion occurs. KIEs imply that increased deuterium in the stratosphere will slow the rate at which HCl reacts with the hydroxyl radical by, approximately, a factor of four. Notwithstanding the improvements of dual-tuning effects of the thermodynamics and kinetics for hydrogen storage materials, these results evidence the need to further investigate, in a systemic rather than piecemeal fashion, the potential impact of anthropogenically released heavy hydrogen on atmospheric radical reactions.