N-Doped Carbon Materials Modified with Cobalt Nanoparticles As Catalysts for Oxygen Reduction Reaction
Authors: Stagniunaite Raminta , Kepeniene Virginija , Sukackiene Zita , Norkus Eugenijus , Tamasauskaite-Tamasiunaite Loreta 
Published: December 2020

The oxygen reduction reaction is one of the main reactions which occur in fuel cells and other renewable energy technologies. In addition to this, oxygen reduction reaction on the cathode is more difficult reaction compare to anodic reaction, because the greater amount of Pt must be used as the cathode material to catalyze the reaction. The search for an efficient electrocatalyst for oxygen reduction reaction to replace platinum in fuel cell
cathode materials is one of the hottest topics in electrocatalysis in relation to platinum high price and limited resources. That is the reason why researches put an effort in finding low cost, higher efficient and great performance catalysts. Various alternative catalysts have been studied including noble or non-noble metal catalysts. It is known that carbon is considered as one of the most promising electrocatalytic material for replacement of Pt. Therefore, researches have been trying multifarious methods with the purpose to increase the activity of the carbon. The fabricated N-doped carbon materials, 2D nitrogen-doped hierarchically porous carbon, N and P co-functionalized three-dimensional porous carbon networks, N, S-codoped porous exfoliated carbon nanosheets, N-doped carbon nanotubes, nitrogen-doped carbide-derived carbon catalysts or nitrogen-rich carbon dots decorated graphene oxide hybrid were described as materials having very similar electrocatalytic activity towards oxygen reduction reaction to Pt. Moreover N-doped carbon catalysts show high electrocatalytic activity forward oxygen reduction reaction in both – acidic and alkaline media. Among the many non-noble metal catalysts, metal/nitrogen/carbon composites containing Fe, Cu, Co metals are a promising alternative to Pt.

In this study, the biological waste, such as black liqueur and alder wood chips, were used for the fabrication of catalytic material. Activated carbon and black liqueur were doped with cheap nitrogen precursor dicyandiamide and used as substrates for the deposition of cobalt nanoparticles (CoNPs) with the aim to use them as electrocatalysts for the oxygen reduction reaction. The synthesized catalysts were characterized by Inductively Coupled Plasma Optical Emission Spectroscopy, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. Activity of the prepared catalysts was evaluated for oxygen reduction reaction in O2 - saturated 0.1 M NaOH solution employing the rotating disk electrode method. Electrocatalytic activity of CoNPs-N-doped black liqueur and CoNPs-N-doped activated carbon catalysts were compared with catalytic activities of commercial Pt/C wt. 46.4 % Pt.

It has been found that the N-doped black liqueur and N-doped activated carbon substrates show high electro-catalytic activity for the oxygen reduction reaction. The modification of N-doped black liqueur and N-doped activated carbon with Co nanoparticles enhanced electrocatalytic activity of catalysts towards oxygen reduction reaction. It has been determined that the N-doped black liqueur and CoNPs- N-doped black liqueur samples demonstrated more similar electrocatalytic activity towards oxygen reduction reaction to Pt/C.