Impact of SO2 poisoning of platinum nanoparticles modified glassy carbon electrode on oxygen reduction

An extraordinary recovery characteristic of Pt-nanoparticles from SO2 poisoning is introduced in this study. Platinum nanoparticles (nano-Pt) modified glassy carbon electrode (nano-Pt/GC) has been compared with polycrystalline platinum (poly-Pt) electrode towards SO2 poisoning. Two procedures of recovery of the poisoned electrodes were achieved by cycling the potential in the narrow potential range (NPR, 0–0.8 V vs. Ag/AgCl/KCl (sat.)) and wide potential range (WPR, −0.2 to 1.3 V). The extent of recovery was marked using oxygen reduction reaction (ORR) as a probing reaction. SO2 poisoning of the electrodes changed the mechanism of the oxygen reduction from the direct reduction to water to the stepwise reduction involving the formation of H2O2 as an intermediate, as indicated by the rotating ring-disk voltammetry. Using the WPR recovery procedure, it was found that two potential cycles were enough to recover 100% of the activity of the ORR on the nano-Pt/GC electrode. At the poly-Pt electrode, however, four potential cycles of the WPR caused only 79% in the current recovery, while the peak potential of the ORR was 130 mV negatively shifted as compared with the fresh poly-Pt electrode. Interestingly, the NPR procedure at the nano-Pt/GC electrode was even more efficient in the recovery than the WPR procedure at the poly-Pt electrode.

Research highlights▶ SO2 poisoning of platinum nanoparticles modified glassy carbon (nano-Pt/GC) and polycrystalline platinum (poly-Pt) electrodes changes the adsorption mode of molecular oxygen. ▶ SO2 poisoning changes the oxygen reduction mechanism from the one-step four-electron reduction to water to the stepwise reduction involving the formation of H2O2 as an intermediate. ▶ Nano-Pt/GC electrode shows an improved resistance to SO2 poisoning compared with the poly-Pt electrode. ▶ The poisoned nano-Pt/GC electrode could be recovered by cycling the potential in the potential range of oxygen reduction reaction. ▶ Platinum oxide has a crucial role in SO2 poisoning and recovery of the Pt electrode.