Re(tBu-bpy)(CO)3Cl Supported on Multi-Walled Carbon Nanotubes Selectively Reduces CO2 in Water.

The selective electrochemical reduction of CO2 to CO in water by a Re(tBu-bpy)(CO)3Cl catalyst incorporated into multi-walled carbon nanotubes (MWCNT) was investigated. Current densities of ∼4 mA/cm2 and selectivities (FECO) of 99% were achieved at -0.56 V vs RHE in CO2-saturated aqueous KHCO3 solutions. The Re(tBu-bpy)(CO)3Cl catalyst has been widely studied as a homogeneous catalyst in organic solvents. Supporting Re(tBu-bpy)(CO)3Cl on MWCNTs increases current densities, decreases overpotential, retains selectivity for reduction of CO2 to CO, and allows operation in water at pH = 7.3 compared to the molecular catalyst in acetonitrile solution. The Re/MWCNT electrocatalysts achieve TON > 5600 and TOF > 1.6 s-1. This electrocatalyst material is efficient, robust, simple to prepare, and scalable.