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 O2-free solutions. However, the purging process to extract O2 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 O2 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 O2. Herein, we accessed the influence of the oxygen reduction reaction on the GEOR by using a flow system with an electrode in wall-jet configuration. The GEOR is investigated on Pt/C nanoparticles (NPs) in the presence of different amounts of O2 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@Au whenever 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 O2 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 O2-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 O2 greatly decreases the stability of Pt@Au during GEOR, mainly due to the improved oxygen reduction and extended surface accessed by O2, while same material controversially displayed good stability in N2-saturated solution. The use of flow configuration shed a light on the influence of O2 on GEOR, providing new information non-accessible by other classic stationary methods.
KeywordsGlycerol electrooxidation reaction Oxygen reduction Stationary system Flow system Electroactive material
We thank LNNano-CNPEM (Campinas, Brazil) for the use of the JEOL JEM 2100F microscope.
The study received financial assistance from CNPq (Grant Nos. 454516/2014-2, 309176/2015-8, and 406779/2016-3), FUNDECT (Grants Nos. 026/2015 and 099/2016), and CAPES and FINEP.
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