Electrocatalytic CO reduction near the theoretical potential in water using Ru complex supported on carbon nanotubes.

We successfully developed a highly efficient electrode for CO reduction using a Ru-complex catalyst ([Ru]) supported on carbon paper coated with multi-walled carbon nanotubes (CPCNT/[Ru]). The CPCNT/[Ru] electrode promoted the CO reduction reaction in aqueous solution near the theoretical potential, and produced formate linearly with a current density of greater than 0.9 mA cm at -0.15 V (versus RHE) for at least 24 h. Due to the outstandingly low overpotential, a monolithic tablet-shaped photo-device was realized by coupling the CPCNT/[Ru] catalyst with amorphous SiGe-jn as a light absorber and IrO as a water oxidation catalyst, and the device produced formate from CO and water in a single-compartment reactor. The nanotubes enhanced the rate for CO reduction at [Ru], and accordingly a solar-to-chemical conversion efficiency of 4.3% for formate production was achieved when the CO reduction and HO oxidation sites had the same area.