Speaker
Description
Global warming requires humanity to reduce atmospheric CO2 significantly - and fast. Chemically, CO2 reduction (i.e. electron attachment) is a vital step for its conversion to less harmful or even useful carbon-based products. One approach to capture CO2 is to freeze it at cryogenic temperatures before chemical modification. Whether or not single electron transfer to CO2 is feasible at these low temperatures and how it proceeds remained unknown.
In our study, we generate isolated electrons on a cryogenic ammonia film by photoexcitation using a pulsed femtosecond laser system. We monitor these solvated electrons using time-resolved photoelectron spectroscopy that provides us with information about their population dynamics and energy. Adding CO2 to the system reduces the electron lifetime and modifies the work function, i.e. surface potential, which we analyse with a rate equation model. In a nutshell, by using these solvated electrons as both, reactant in the electron transfer reaction and spectator of the same, we do not only show that single electron CO2 reduction is possible at 50 K, but also determine the electron transfer time of 77 ± 6 ps. Remarkably, no side reactions are observed: for sufficiently long solvated electron lifetimes, every electron reacts. These results provide mechanistic insights into a notoriously difficult yet technologically critical electron transfer reaction.
