The influence of KOH concentration, oxygen partial pressure and temperature on the oxygen reduction reaction at Pt electrodes

• ORR kinetics is inhibited and its pathway shifts as concentration of KOH increases.
• The pathway is confirmed by electrogenerated chemiluminescence and UV.
• An optimal temperature for ORR is obtained in given alkaline solutions.

In this paper, cyclic voltammetry (CV), linear sweep voltammetry (LSV) and rotating ring-disk electrode (RRDE) techniques were employed to investigate the influence of alkali concentration, oxygen partial pressure, and temperature on oxygen reduction reaction (ORR) at Pt electrodes in KOH solutions. It was found that as the KOH concentration increases, the ORR kinetics is greatly inhibited, and the ORR pathway gradually shifts from 4 electrons transfer reaction by directly forming OH− to 2 electrons transfer reaction by forming HO2−. The intermediate species were detected by electrogenerated chemiluminescence and ultraviolet–visible spectrophotometer to confirm the alkali concentration-dependent ORR pathway. In addition, the ORR kinetics was found to be significantly improved by the increasing oxygen partial pressure due to the corresponding increase of oxygen solubility. However, the temperature exhibits dual effects toward ORR and the optimal temperature for the ORR was obtained in given alkaline solutions. The activation energy of ORR was calculated based on the RRDE data.