A Hybrid Co Quaterpyridine Complex/Carbon Nanotube Catalytic Material for CO₂ Reduction in Water

Associating a metal-based catalyst to a carbon-based nanomaterial is a promising approach for the production of solar fuels from CO₂. Upon appending a Co^II quaterpyridine complex [Co(qpy)]²⁺ at the surface of multi-walled carbon nanotubes, CO₂ conversion into CO was realized in water at pH 7.3 with 100 % catalytic selectivity and 100 % Faradaic efficiency, at low catalyst loading and reduced overpotential. A current density of 0.94 mA cm⁻² was reached at −0.35 V vs. RHE (240 mV overpotential), and 9.3 mA cm⁻² could be sustained for hours at only 340 mV overpotential with excellent catalyst stability (89 095 catalytic cycles in 4.5 h), while 19.9 mA cm⁻² was met at 440 mV overpotential. Such a hybrid material combines the high selectivity of a homogeneous molecular catalyst to the robustness of a heterogeneous material. Catalytic performances compare well with those of noble-metal-based nano-electrocatalysts and atomically dispersed metal atoms in carbon matrices.