Electrode-Ligand Interactions Dramatically Enhance CO₂ Conversion to CO by the [Ni(cyclam)](PF₆)₂ Catalyst

Abstract

Dramatic enhancement of electrochemical CO2 conversion to CO, catalyzed by [Ni­(cyclam)]­(PF6)2 is observed on mercury/gold electrodes. We find that Hg provides favorable noncovalent dispersive interactions with the cyclam ligand. As a result, the Hg surface destabilizes the poisoned CO-bound form of the catalyst, leading to enhanced reaction kinetics. These findings are particularly relevant to the design of ligands that improve the electrocatalytic performance of transition-metal complexes on interaction with metallic surfaces under cell operating conditions.

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

“…21c). 246 217,226 Analogous trends correlating the planarity of the ligand scaffold to a more efficient CO release step were also previously discussed for other families of molecular catalysts (see Section 4). 288 The unique properties of Ni-N 4 motifs in promoting an efficient CO 2 RR have been demonstrated in several other recent reports.…”

Electro- and Solar-Driven Fuel Synthesis with First Row Transition Metal Complexes

“…90,464,471 DFT indicates that the trans -III isomer adsorbs most strongly on Hg surfaces and forms a higher energy Ni + –CO adduct which is further destabilized by interaction with the Hg 0 . 90,464 This combination of electronic effects and conformational selectivity speeds up the rate-determining step and avoids CRC deactivation, highlighting the importance of both product clearance and surface interaction.…”

“…The working electrode (WE) material can also have a significant influence on the apparent catalytic activity through direct reaction with the substrate or by altering the properties of the molecular catalyst under investigation. 23,88−90 The above factors should be considered when comparing transition metal-containing molecular complexes, particularly if meaningful structure–activity relationships for improving catalysts are to be revealed.…”

Fast and Selective Photoreduction of CO2 to CO Catalyzed by a Complex of Carbon Monoxide Dehydrogenase, TiO2, and Ag Nanoclusters

“…1–3 An inspirational approach to photo-H 2 production has been to exploit the extremely high catalytic activity of hydrogenases by attaching them directly to light- harvesting systems. 4–6 Direct reduction of a concentrated source of CO 2 (as present in flue gas) is far more challenging than H 2 production, 7–13 but once again, insight has been derived from metalloenzymes such as carbon monoxide dehydrogenase (CODHs: Ni and Fe) 14 or formate dehydrogenase (FRDs: Mo or W), each of which is highly active in catalyzing two-electron reduction of CO 2 with extreme selectivity, avoiding the thermodynamically easier H 2 evolution. 15–18 Importantly, the activities of these enzymes are so high 19 that the performance of the integrated photocatalytic systems in which they are incorporated is limited not by catalysis but by photophysical restrictions and charge-transport connections.…”