Synergistic Effect of Chlorine and Reaction Parameter Effect on Addition of Sulphur to CNTs and Their use as Electrocatalysts for ORR and OER

Abstract

<title>Abstract</title> Electrocatalysts with high activity towards both oxygen reduction and evolution reaction are desirable for metal-air batteries. However, most commercially used electrocatalysts result in sluggish kinetics for these oxygen reactions, and different catalysts are usually used for each oxygen reaction. The development of efficient electrocatalysts that can facilitate both reactions, with low overpotentials resulting in less energy consumption is desirable. Herein we report secondary data analysis for materials developed in our previous study, FeS2 electrocatalyst supported on chlorinated carbon nanotubes (ClCNTs) using chemicals that are not harsh chemicals and investigated its catalytic activity towards ORR and OER. FeS2 nanoparticles were produced by thermal annealing of ClCNTs in thiophene at different annealing temperatures. The effect of thiophene volume and reaction time on the growth of FeS2 nanoparticles was also evaluated. The size of FeS2 nanoparticles coated on the surface of ClCNTs increased with an increase in thermal annealing reaction time, and this reduced the catalytic activity of the materials. Whereas as the volume of thiophene was increased during the production of FeS2-loaded ClCNTs, no FeS2 nanoparticles were observed on the surface of the ClCNTs. ClCNTs annealed at 900 °C showed the greatest growth of FeS2 nanoparticles on their surface and provided the greatest enhancement of the ORR and OER activities, evidenced by the low Tafel slope of 63 mV/dec and low overpotential of 252 mV. The number of electrons involved during the reduction of oxygen was found to be 4, which means that the formation of water was favorable when using this electrocatalyst. In our previous study only, cyclic voltammetry was used to evaluate the electrocatalytic activity of the materials toward ORR.