Robust Binding of Disulfide-Substituted Rhenium Bipyridyl Complexes for CO2 Reduction on Gold Electrodes

GUO, FACHENG; KIEFER, LAURA; LIU, QILIANG; BATISTA, VÍCTOR S.; KELLY, H. RAY; GEBRE, SARA; WU, SHAOXIONG; CATTANEO, MAURICIO; VIDELA, PABLO E.; GE, AIMIN; LIAN, TIANQUAN

Frontiers in Chemistry

Frontiers Media

Año: 2020 vol. 8

Heterogenization of homogenous catalysts on electrode surfaces provides a valuableapproach for characterization of catalytic processes in operando conditions usingsurface selective spectroelectrochemistry methods. Ligand design plays a centralrole in the attachment mode and the resulting functionality of the heterogenizedcatalyst as determined by the orientation of the catalyst relative to the surfaceand the nature of specific interactions that modulate the redox properties underthe heterogeneous electrode conditions. Here, we introduce new [Re(L)(CO)3Cl]catalysts for CO2 reduction with sulfur-based anchoring groups on a bipyridyl ligand,where L = 3,3′-disulfide-2,2′-bipyridine (SSbpy) and 3,3′-thio-2,2′-bipyridine (Sbpy).Spectroscopic and electrochemical analysis complemented by computational modelingat the density functional theory level identify the complex [Re(SSbpy)(CO)3Cl] asa multi-electron acceptor that combines the redox properties of both the rheniumtricarbonyl core and the disulfide functional group on the bipyridyl ligand. The firstreduction at −0.85 V (vs. SCE) involves a two-electron process that breaks the disulfidebond, activating it for surface attachment. The heterogenized complex exhibits robustanchoring on gold surfaces, as probed by vibrational sum-frequency generation (SFG)spectroscopy. The binding configuration is normal to the surface, exposing the activesite to the CO2 substrate in solution. The attachment mode is thus particularly suitablefor electrocatalytic CO2 reduction.