This Keynote talk will present recent mechanistic insights gleaned from state-of-the-art quantum mechanics computations of photoelectrocatalytic and electrocatalytic reduction of CO2 to a variety of products, including formic acid, methanediol, and methanol, among others. The product distribution depends is, unsurprisingly, highly electrode-dependent. For photoelectrochemical reduction, we find that hydride transfer dominates the chemistry, rather than proton-coupled electron transfer. Further, we find CdTe stops at formic acid (as seen experimentally), metal-rich facets of GaP stop at methanediol, while reduction all the way to methanol occurs on other facets of GaP and CuInS2. For electrocatalysis on metal electrodes, we show the critical need to describe electron transfer using embedded correlated wavefunction theory rather than pure density functional theory, in order to obtain electrochemistry consistent with observed onset potentials. Mechanistic predictions are strikingly different between the two theories, suggesting a need to revisit past mechanistic assessments that have used the less expensive method.

Mechanisms of (photo)electrochemical conversion of CO2 to fuels from first principles

ACS Fall 2021

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