Chelating N‐Heterocyclic Carbene Ligands Enable Tuning of Electrocatalytic CO₂ Reduction to Formate and Carbon Monoxide: Surface Organometallic Chemistry

Abstract

Reported here is the chelate effect as ad esign principle for tuning heterogeneous catalysts for electrochemical CO 2 reduction. Palladium functionalizedw ith ac helating tris-N-heterocyclic carbene (NHC) ligand (Pd-timtmb Me ) exhibits a3 2-fold increase in activity for electrochemical reduction of CO 2 to C1 products with high Faradaic efficiency (FE C1 = 86 %) compared to the parent unfunctionalized Pd foil (FE = 23 %), and with sustained activity relative to am onodentate NHC-ligated Pd electrode (Pd-mimtmb Me ). The results highlight the contributions of the chelate effect for tailoring and maintaining reactivity at molecular-materials interfaces enabled by surface organometallic chemistry.

Transition metal-based catalysts for the electrochemical CO2reduction: from atoms and molecules to nanostructured materials

“…448 Chelating multidentate NHC ligands have been successfully used for CO 2 electroreduction in homogeneous molecular catalysts [449][450][451][452] and polycrystalline metallic surfaces (vide infra). 453 The strong s-donating character of the NHC ligands is particularly attractive for CO 2 RR, leading to electron-rich metal surfaces with an enhanced reactivity towards CO 2 . Moreover, their ability to form highly stable M-C bonds with transition metal atoms enables to improve the catalyst stability under electrochemical reductive conditions, preventing nanoclustering deactivation effects.…”

Dramatic HER Suppression on Ag Electrodes via Molecular Films for Highly Selective CO2 to CO Reduction

“…[18][19][20] In this context, molecular modifications of electrode surfaces provide an attractive approach for the electrosynthesis of desired products in CO2RR. [21][22][23][24][25][26][27][28][29] Our research team has recently focused on studying the interaction of molecular films with copper electrodes to control the selectivity of CO2RR. [30][31][32] We have disclosed that water-soluble N-substituted pyridinium-type additives undergo electrochemically induced reductive dimerization in situ, leading to the deposition of an organic film onto the surface of a polycrystalline Cu electrode.…”

Temperature Effects on CO2 Electroreduction Pathways in an Imidazolium-Based Ionic Liquid on Pt Electrode

“…The two groups of Tafel data (Table S3) establish that [Emim]­[NTf 2 ] follows the many mechanistic pathways different from [Bmpy]­[NTf 2 ] for electrochemical CO 2 reduction. [Bmpy]­[NTf 2 ] gives rise to a Tafel slope range from 97 to 126 mV dec –1 at different temperatures, which is close to the 118 mV dec –1 indexing a rate-determining one-electron transfer for the formation of CO 2 •– from the adsorbed CO 2 . , By contrast, the slopes in [Emim]­[NTf 2 ] are observed in the range of 47 to 82 mV dec –1 . These are much closer to 59 mV dec –1 , supporting the mechanism that the reduced [Emim] layer on the electrode occurs before a single-electron transfer to form CO 2 •– prior to a rate-limiting chemical step .…”

“…As illustrated in Figure S4f Tafel plots have been widely used to evaluate kinetic parameters of redox reactions, especially for irreversible or •− from the adsorbed CO 2 . 49,50 By contrast, the slopes in [Emim][NTf 2 ] are observed in the range of 47 to 82 mV dec −1 . These are much closer to 59 mV dec −1 , supporting the mechanism that the reduced [Emim] layer on the electrode occurs before a single-electron transfer to form CO 2…”