Electrochemically CO2 conversion using homogeneous and nanostructured heterogeneous Ru (II) electrocatalysts

Abstract

The reduction of carbon dioxide to desirable products is an urgent goal in favour of the environment, the energy-cycle and mankind. We report the electrochemical reduction of CO2 to carbon monoxide by means of the homogeneous electrocatalyst (1), [Ru(bpy)2(L1)](ClO4)2, and the heterogeneous one (2), [Ru(bpy)2L1](ClO4)2@SiO2-NH2@Fe3O4) (meaning 1 fixed onto functionalized nanoparticles). The catalysts have been synthesized and characterized using different spectroscopies (IR, UV–vis, EDAX, SEM and PXRD(. The crystal structure of 1, determined by X-ray diffraction, revealed a distorted octahedral coordination of the Ru (II) center. In 1 the electrocatalytic activity of the complex was investigated for the CO2 reduction under various reaction conditions; this complex is stable and active for the CO2 reduction to CO in 0.5 M of a TBHP acetonitrile electrolyte. Under heterogeneous condition, both 1 and 2 show small electrocatalytic activity for CO2 reduction and remarkable electrocatalytic activity for H2 evolution in 0.5 M KHCO3 aqueous electrolyte, which can be attributed to the HCO3¯ mediated hydrogen evolution reaction (HER) process. It is expected that this could introduce a new type of the electrocatalysts for syngas production from CO2 and H2O in both homogeneous and heterogeneous catalytic systems.