Synergistic electrocatalysis of N,Nʹ-bis(salicylidene)-ethylenediamine-cobalt(II) and conductive carbon black (BP) for high efficient CO₂ electroreduction

Gas diffusion electrodes (GDEs) modified with N,Nʹ-Bis(salicylidene)-ethylenediamine-cobalt(II) (Cosalen) and conductive carbon black (BP) have been prepared. It is demonstrated that modified BP-Cosalen/GDE electrode is able to catalyze CO₂ reduction in a more efficient and selective manner than that of bulk Cosalen/GDE in 0.5 M KHCO₃ solution. In the presence of 60 wt% of BP, the as-prepared BP-Cosalen/GDE electrode exhibits the highest activity for catalyzing CO₂ reduction reaction, wherever increase or decrease the amount of BP do not benefit to CO₂ reduction. Compared to other BP-Cosalen/GDE electrodes, the BP-Cosalen/GDE60 shows the most positive onset potential, and the maximum current density reaches 21 mA cm⁻². The improved catalytic activity is largely due to the excellent electrical conductivity and the developed pore structure of BP which provides more active phases for the electrochemical reduction of CO₂. Further analysis of reduction product reveals that the product on BP-Cosalen/GDE60 electrode is formate in 0.5 M KHCO₃ electrolyte. The highest faradaic efficiency reached 27 % along with the production rate of formate as much as 0.44 mM.