Identifying a Key Factor Determining Interfacial Electron Transfer in CO₂ Reduction to Formate: Potential of Zero Charge

Abstract

Electron transfer at the metal−solution interface is crucial to an electrocatalytic reaction, which is generally recognized as a rate-determining step. So far, there is still lack of a universal experimental electrochemical quantity strongly correlated with the interfacial electron transfer rate for different kinds of catalysts, limiting the design of superior electrocatalysts for a given electrocatalytic reaction. Here, we propose that the potential of zero charge (PZC) is theoretically and experimentally correlated with the interfacial electron transfer rate and thus profoundly affects the activity and selectivity of CO 2 electroreduction to formate for Bi, In, Sn, and Pb. PZC takes into account the contributions from both the work function of catalysts and the change in the electron overlapping distribution at the catalyst surface induced by the solvent dipoles. The higher the PZC, the faster the interfacial electron transfer rate of CO 2•− formation in the process of CO 2 electrochemical reduction to formate. Thus, the promotion by accelerating the interfacial electron transfer leads to higher electrocatalytic activity and selectivity for yielding formate. This study demonstrates the relationships between PZC and activity and selectivity, and further lays a theoretical foundation for in-depth insight into the electrocatalytic mechanism of different kinds of metals on highly yielding the same product.

Insights into Electrochemical CO2 Reduction on Metallic and Oxidized Tin Using Grand-Canonical DFT and In Situ ATR-SEIRA Spectroscopy

“…One pathway creates OCHO* adsorbed via surface-oxygen(s) bonds, while the other creates COOH* adsorbed via a surface-carbon bond . However, it is also often proposed that the first elementary step of CO 2 R (to either product) is the single-electron reductive adsorption CO 2 + * + e – → CO 2 – . ,,, The CO 2 –* intermediate can be bound through the carbon atom or the oxygen atom(s), which can be protonated to form COOH* or OCHO*, respectively. We therefore considered both the single-electron reductive adsorption and each of the PCET pathways to activate CO 2 .…”

In Situ Dissociated Chalcogenide Anions Regulate the Bi-Catalyst/Electrolyte Interface with Accelerated Surface Reconstruction toward Efficient CO2 Reduction

“…Generally, anions would display specific adsorption behaviors on the electrode/electrolyte interface, especially for chalcogenide anions. , To further reveal the role of M anions (S 2– , Se 2– , and Cl – ) in the formation of active Bi–O structures, first-principles molecular dynamics (AIMD) is employed to investigate the changes in surface WF and PZC for Bi (110) crystal surface with the presence of M anions (Figures a,b and S33–S37). The WFs of Bi with the adsorption of S 2– , Se 2– and Cl – in aqueous solution are calculated to be 4.25, 4.24, and 4.31 eV, respectively, lower than 4.35 eV of metallic Bi . The PZCs of Bi with the specific adsorption of S 2– , Se 2– , and Cl – are estimated to be −0.19, −0.20, and −0.13 V, which are more negative compared to those of metallic Bi (−0.09 V).…”

“…The WFs of Bi with the adsorption of S 2− , Se 2− and Cl − in aqueous solution are calculated to be 4.25, 4.24, and 4.31 eV, respectively, lower than 4.35 eV of metallic Bi. 45 The PZCs of Bi with the specific adsorption of S 2− , Se 2− , and Cl − are estimated to be −0.19, −0.20, and −0.13 V, which are more negative compared to those of metallic Bi (−0.09 V). The reduced WFs and negatively shifted PZC may promote the surface oxidation of Bi and benefit the formation of the CO 2 RR active Bi−O structures.…”