Cation-Coordinated Inner-Sphere CO₂ Electroreduction at Au–Water Interfaces

Abstract

Electrochemical CO2 reduction reaction (CO2RR) is a promising technology for the clean energy economy. Numerous efforts have been devoted to enhancing the mechanistic understanding of CO2RR from both experimental and theoretical studies. Electrolyte ions are critical for the CO2RR; however, the role of alkali metal cations is highly controversial, and a complete free energy diagram of CO2RR at Au–water interfaces is still missing. Here, we provide a systematic mechanism study toward CO2RR via ab initio molecular dynamics simulations integrated with the slow-growth sampling (SG-AIMD) method. By using the SG-AIMD approach, we demonstrate that CO2RR is facile at the inner-sphere interface in the presence of K cations, which promote the CO2 activation with the free energy barrier of only 0.66 eV. Furthermore, the competitive hydrogen evolution reaction (HER) is inhibited by the interfacial cations with the induced kinetic blockage effect, where the rate-limiting Volmer step shows a much higher energy barrier (1.27 eV). Eventually, a comprehensive free energy diagram including both kinetics and thermodynamics of the CO2RR to CO and the HER at the electrochemical interface is derived, which illustrates the critical role of cations on the overall performance of CO2 electroreduction by facilitating CO2 adsorption while suppressing the hydrogen evolution at the same time.

The importance of a charge transfer descriptor for screening potential CO2 reduction electrocatalysts

“…For simplicity, we assumed that these conclusions hold also for all other considered metal surfaces, an approximation that has to be verified by future simulations. In line with our settings, a recent work has suggested that the transition state of the *CO 2 to *COOH step lies close to *COOH with no additional kinetic barrier, but proposed an additional barrier for CO 2 adsorption which we did not consider here 130 .…”

Solvation of furfural at metal|water interfaces: Implications for aqueous phase hydrogenation reactions

“…Ab initio molecular dynamics (AIMD) provides direct atomistic level insights on adsorption phenomena and catalysis at metal|water interfaces [31][32][33][34][35][36][37] . For instance, Heenen et al studied the adsorption of several common adsorbates (CO*, CHO*, COH*, OCCHO*, OH* and OOH*) on Cu, Au and Pt metal|water interfaces, and found the solvation energies to be dependent on both the identity of the adsorbate and the metal surface.…”

Weakly Coordinating Organic Cations are Intrinsically Capable of Supporting CO2 Reduction Catalysis

“…8,9 Despite the widespread observation of cation effects on the CO2RR, the mechanistic basis for these trends remains the subject of intense debate. [8][9][10][11][12][13][14][15][16][17][18][19][20] Leading explanations put forward bifurcate into two broad categories: (a) cations induce changes to the mean-field electrostatic potential profile at the interface; [15][16][17][18] and (b) cations are involved in coordinative chemical interactions with adsorbed reaction intermediates. 11,12,19,21 The former electrostatic model postulates a sharper electrostatic potential drop in the presence of weakly hydrated cations such as Cs + relative to strongly hydrated ions such as Li + .…”