Impact of toluene contamination on the oxygen reduction at polycrystalline platinum electrode: Poisoning and mitigation

Abstract

Cyclic and hydrodynamic voltammetric measurements have been used to examine mechanistically the oxygen reduction reaction (ORR) at toluene-poisoned polycrystalline platinum (poly-Pt) electrode to explore the effect of poisoning with toluene, as a hydrocarbon model, on the electrochemical behavior of ORR at poly-Pt electrode. For this purpose, ORR is used as a marker reaction for the poisoning extent and for the ease of the in-situ mitigation of the poly-Pt electrode activity. The in-situ recovery at various scenarios is examined as it is crucial for the development of proton-exchange membrane fuel cells (PEMFs). Rotating ring-disk electrode voltammetry proved that the toluene-poisoning of poly-Pt electrode results in the change in ORR mechanism from the direct reduction of O2 to H2O to the reduction of O2 to H2O2 followed by further reduction to H2O. Voltammetric studies shows a preferential adsorption of toluene on the various facets of poly-Pt electrode. Recovery scenario in which the potential of the electrode was scanned in the range −0.2 to 1.3 V was found to be remedial in complete recovery of the poisoned electrode. Using RRDE, it has been shown that the limiting current in 100 ppm toluene contaminated H2SO4 at the previously reduced and oxidized electrodes to decrease to 60% and 20% of the value obtained in the absence of toluene.