Re(tBu-bpy)(CO) 3 Cl Supported on Multi-Walled Carbon Nanotubes Selectively Reduces CO 2 in Water.

The selective electrochemical reduction of CO ₂ to CO in water by a Re(tBu-bpy)(CO) ₃ Cl catalyst incorporated into multi-walled carbon nanotubes (MWCNT) was investigated. Current densities of ∼4 mA/cm ² and selectivities (FE _CO ) of 99% were achieved at -0.56 V vs RHE in CO ₂ -saturated aqueous KHCO ₃ solutions. The Re(tBu-bpy)(CO) ₃ Cl catalyst has been widely studied as a homogeneous catalyst in organic solvents. Supporting Re(tBu-bpy)(CO) ₃ Cl on MWCNTs increases current densities, decreases overpotential, retains selectivity for reduction of CO ₂ 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.