Inhibiting Hydrogen Evolution using a Chloride Adlayer for Efficient Electrochemical CO₂ Reduction on Zn Electrodes

Abstract

A challenge in electrochemical CO 2 reduction is inhibiting hydrogen evolution reaction (HER). Herein, a bulk Zn electrode was chosen to reveal the effect of specifically adsorbed Cl − ions on HER during CO 2 reduction. We found that in the Cl − ion-containing electrolyte, the Zn−Cl adlayer formed because the weakly solvated Cl − ions can strip the solvation shell and form a direct chemical bond with the metal Zn. As a result, the Zn−Cl bonds on the Zn electrode notably blocked the hydrogen evolution and significantly facilitated the electron transfer process via the Cl to the vacant orbitals of inert CO 2 , therefore stabilizing the CO 2 − radical and leading to a four times higher CO Faradaic efficiency for CO 2 reduction in the KCl electrolyte than that in the KHCO 3 electrolyte at a moderate potential of −1.2 V versus a reversible hydrogen electrode.

Controlled Formation of Dimers and Spatially Isolated Atoms in Bimetallic Au‐Ru Catalysts via Carbon‐Host Functionalization

“…The high sensitivity of the HER to the metal speciation enabled to probe and discern the different catalytic fingerprints of Au‐Ru dimers and isolated atoms, unveiled by the more prominent promotional effect of Au atoms on Ru atoms in the presence of intermetallic bonds. To this end, although [Au 1 ‐Ru 1 ] SA /NC presents a higher chlorination degree with respect to [Au 1 ‐Ru 1 ] D /AC (Au‐Cl CN = 1.7 and 0.9, respectively, and Ru‐Cl CN = 2.8 and 1.2, respectively, Table S1, Supporting Information), which may affect the activity for the HER, [ 31 ] both samples present a similar decrease in the chlorination degree compared to their Ru SACs counterparts (Ru‐Cl CN = 4.3 and 3.2, respectively, Table S1, Supporting Information). Therefore, the normalization of the catalytic activity of the bimetallic catalysts with respect to the activity of the Ru SACs on the same support accounts for the potential activity enhancement due to the lower chlorination degree of the bimetallic catalysts with respect to the Ru SACs, enabling a reliable comparison and discernment between the synergistic interplays in [Au 1 ‐Ru 1 ] D /AC and [Au 1 ‐Ru 1 ] SA /NC.…”

Recent Advances in Interface Engineering for Electrocatalytic CO2 Reduction Reaction

“…for selective CO production [237][238][239][240][241][242]. The adsorption of CN − and Cl − on Au surface is demonstrated to give a higher current density than the pristine one for CO production [243].…”

“…The selectivity of Cu-based electrodes to CH 4 , C 2 H 4 , formate, and C 2 H 5 OH was reported to be increased in the presence of halide [ 232 – 234 ]. In addition, the effects of halide on the activity of Ag and Zn have also been investigated for selective CO production [ 237 – 242 ]. The adsorption of CN − and Cl − on Au surface is demonstrated to give a higher current density than the pristine one for CO production [ 243 ].…”

A comparative study of the effects of different TiO2 supports toward CO2 electrochemical reduction on CuO/TiO2 electrode

“…1,2 However, signicant competition between CO 2 reduction and hydrogen evolution in aqueous solution occurs, leading to the low efficiency and product selectivity. 3,4 Therefore, the application of CO 2 reduction is rather limited.…”