Influence of pre-treatment on the catalytic activity of carbon and its Co-based catalyst for oxygen reduction reaction

• Methods involving thermal treatment, H2O2-oxidation and KOH-activation are used.
• Carbon pre-treatment has an effect on the catalytic activity and selectivity.
• Pre-treatment shows different effect in acid and alkaline electrolyte.
• Pre-treatment can decrease the disorder of carbon matrix.
• Carbon pre-treatment can decrease the size of Co particles in the catalysts.

Impact of carbon pre-treatment on the catalytic activity and selectivity of its own and its relevant non-precious metal Co-based catalyst (carbon-supported cobalt diethylenetriamine, CoDETA/C) for oxygen reduction reaction is investigated. Three pre-treatment methods involving thermal treatment, H2O2-oxidation and KOH-activation are used in this paper. Electrochemical activity demonstrated by cyclic voltammograms and rotating ring disk electrode technique in O2-saturated electrolyte shows that pre-treatment step has a significant effect on the catalytic activity and selectivity of carbon and its Co-based catalyst: (1) for carbon sample, a KOH-activation gives the highest activity in acid medium, while a H2O2-oxidation in alkaline solution; and (2) for its Co-based catalyst, the as-ground gives the highest activity and selectivity in acid solution, while a KOH-activation in alkaline medium. Raman spectra indicate that pre-treatment can decrease the disorder of carbon matrix. X-ray diffraction shows that face-centered cubic α-Co phases are present and pre-treatment of carbon can decrease the size of metal Co dispersed on the catalyst surface.