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 (FE_CO) 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.