First Assessments of the Influence of Oxygen Reduction on the Glycerol Electrooxidation Reaction on Pt

The electroactivity of new nanomaterials candidates to be used as anodes for glycerol fuel cells or electrolysers has been largely investigated, but most of the literature reports the use of O-2-free solutions. However, the purging process to extract O-2 from glycerol solution and the storage at similar condition is costly. Moreover, the lack of knowledge on the glycerol electrooxidation reaction (GEOR) in the presence of O-2 prevents alternative applications, as that in single channel microfluidic fuel cells, when the anode must be selective for the alcohol oxidation in the presence of O-2. Herein, we accessed the influence of the oxygen reduction reaction on the GEOR by using aflow system with an electrode in wall-jet configuration. The GEOR is investigated on Pt/C nanoparticles (NPs) in the presence of different amounts of O-2 in solution as a proof of concept. We also used synthesized Pt@Au to apply the method for a new material candidate to be used as catalyst in glycerol technologies. The presence of oxygen in solution barely influences GEOR on Pt/C or Pt@Auwhenever classic stationary measurements are used. We found comparable electrocatalytic parameters and the same carbonyl products, but at slightly different proportions, in the presence or absence of O-2 after long-time electrolysis followed by chromatographic analysis. On the other hand, oxygen competes with glycerol by the active sites when the reactants are convectively forced towards the electrode surface, at flow configuration. The competition between GEOR and oxygen reduction results in a net cathodic current density when using O-2-saturated glycerol solution at potentials suitable for the reduction reaction on Pt/C. Pt@Au shows remarkable activity for the oxygen reduction, producing high cathodic currents even in air-saturated glycerol solution. Moreover, the presence of O-2 greatly decreases the stability of Pt@Au during GEOR, mainly due to the improved oxygen reduction and extended surface accessed by O-2, while same material controversially displayed good stability in N-2-saturated solution. The use of flow configuration shed a light on the influence of O-2 on GEOR, providing new information non-accessible by other classic stationary methods.