We evaluated the reactivity of electrons (both non-solvated and solvated) in CO2/water mixtures at different gas pressures (from 1 to 118 bar) and temperatures (25 and 35°C) using picosecond radiolysis. A custom spectroscopic cell was designed for these high-pressure gas experiments, allowing for the direct measurement of electron trapping, even in a supercritical state. Our results revealed a non-monotonic dependence of electron reactivity on CO2 concentration in water modified under atmospheric pressure effects [Hu2021, Denisov2021, Dobrovolskii2023, Hu2023]. In our quest to achieve the highest conversion yield of CO2 under mild conditions of ambient temperature, neutral pH, and 1 atm CO2 pressure, we developed a new approach leveraging primary radicals generated from water irradiation. To ensure the reduction of CO2 to CO2•− by all primary radicals from irradiated water, we used formate ions to simultaneously trap the parent oxidizing radicals H• and OH•, thereby producing the same transient CO2•− radicals. This strategy enabled us to utilize all available radicals to selectively convert CO2 into oxalate, accompanied by the release of H2, without the need for catalysts and at ambient temperature. Furthermore, we developed a new approach for the time-resolved identification of intermediates bound to the surfaces of metallic nanocatalysts. This approach, combined with molecular simulations, allowed for the identification of surface-bound intermediates exhibiting transient absorption bands characteristic of the nanosecond to second timescale for three typical metallic nanocatalysts: Cu, Au, and Ni [Jiang2023], as illustrated in the figure.

Time-resolved absorption of the stabilization process of CO2•− with different metallic nanoparticles (Gold, Copper, Nickel)