Impact of Glass Corrosion on the Electrocatalysis on Pt Electrodes in Alkaline Electrolyte

Abstract

We report on the influence of glass corrosion on establishing the electrocatalytic activity of fuel cell catalysts. A Teflon electrochemical cell was designed for measurements in alkaline electrolyte. The cell performance was tested and compared to a standard electrochemical glass cell by measuring the oxygen reduction reaction and the hydrogen oxidation reaction on polycrystalline platinum in 0.1 M KOH. It is demonstrated that in the Teflon cell the shape of the cyclic voltammogram as well as the activity for the reactions are reproducible and do not alter over a long period of time. By comparison, using the standard electrochemical cell made out of Duran glass, it is found that the experiments on polycrystalline Pt electrodes in alkaline electrolyte are insufficiently reproducible. The cyclic voltammograms alter over time, and the activities of the hydrogen oxidation as well as the oxygen reduction depend on the applied potential scan limits. This is due to the contamination of the electrolyte because of the etching of glass by KOH, which is further supported with an analysis of the alkaline electrolyte after usage in the respective cell types by inductively coupled plasma-optical emission spectroscopy. The oxygen reduction reaction ͑ORR͒ and the hydrogen oxidation reaction ͑HOR͒ are the key reactions in electrochemical energy conversion devices, such as fuel cells and batteries. Tremendous efforts have been directed especially into improving the electrocatalysts for the ORR in acid electrolytes over the last decades, in order to render proton exchange membrane fuel cells ͑PEMFCs͒ commercially viable.

On the oxygen reduction reaction in phosphoric acid electrolyte: Evidence of significantly increased inhibition at steady state conditions

“…All electrochemical measurements were conducted in an in house developed three-compartment electrochemical cell made out of Teflon [36,37]. A saturated calomel electrode (SCE), separated from the working electrode compartment by a membrane, was used as the reference electrode [38].…”

Bulk-Palladium and Palladium-on-Gold Electrocatalysts for the Oxidation of Hydrogen in Alkaline Electrolyte

“…The choice of PTFE as opposed to glass for the measurements in alkaline media was motivated by the detrimental effects of glass corrosion products on the HOR/HER-kinetics of Pt. 30 The PTFE cell was embedded in a stainless steel jacket connected to a calibrated thermostat (Julabo Labortechnik GmbH, Seelbach, Germany) at 293 K, and it was closed with a four-necked glass cover which has no contact to electrolyte. The glass cell used with acid electrolytes also had four necks, and thus both setups consisted of similar working, reference and counter electrodes, along with a gas bubbler that allowed for gas blanketing above the surface of the electrolyte or direct bubbling through a fluorinated ethylene propylene (FEP) tube.…”

Kinetics of the Hydrogen Oxidation/Evolution Reaction on Polycrystalline Platinum in Alkaline Electrolyte Reaction Order with Respect to Hydrogen Pressure

“…On the other hand, Sheng and collaborators 9 have recently estimated essentially identical HOR/HER exchange current densities of ≈0.7 mA · cm Pt −2 (at 293 K) for polycrystalline Pt and carbon-supported Pt nanoparticles of ≈2 nm diameter, which would suggest the absence of structure sensitivity for the HOR/HER, contrary to the well-known structure sensitivity of the ORR on Pt 6,12,13 and to the results of the HOR/HER studies on Pt single crystals 11,14,15 discussed above. One may speculate that this discrepancy might arise from the contamination of the Pt(hkl) surfaces with electrolyte impurities resulting from the leaching of glass components in the electrochemical cell upon contact with the alkaline solution, 16,17 which was successfully suppressed in Ref. 9 by minimizing the measurement delay.…”