A DFT and microkinetic modeling study of pressure effects on electroreduction reduction of CO2 to ethanol

Abstract

The CO₂ electroreduction reaction (CO₂RR) is a promising way to convert surplus renewable electricity into valuable low-carbon fuel. Ethanol is one of the most beneficial products because of its high energy density, ready transport, and extensive use. The CO₂ partial pressure (P_CO2) significantly impacts ethanol formation. This work explores the mechanism of pressure dependence in ethanol formation on the Cu₂O/Cu(1 1 1) surface via the density functional theory (DFT) and microkinetic model calculations. DFT results show that *CO is the major adsorbate on the catalyst surface, and its coverage is the descriptor of pressure. Initially, increasing the coverage of *CO promotes the C–C coupling to ethanol, while the excess coverage shifts the potential determining step (PDS) from the *CHO formation to the *CHO–*CO addition, prejudicing the ethanol formation. The degree of selectivity control (DSC) results show that *CO stability positively affects ethanol production, while the stabilities of *H and *CH₃CH₂OH exhibit the reverse. Their effects decrease and increase with pressure increase, respectively, leading to the volcano plot of the pressure dependence on ethanol formation. The mechanistic insights gained from this work provide relevant guidelines to optimize the reaction pressure conditions for the CO₂RR to ethanol reaction.