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

Abstract

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.

Keywords: carbon dioxide reduction; cobalt complexes; electrochemical catalysis; hybrid materials; supported homogeneous catalysis.