Are Radicals Formed During Anion-Exchange Membrane Fuel Cell Operation?

Abstract

In this paper we present a study on stable radicals and short-lived species generated in anion-exchange membrane (AEM) fuel cells (AEMFCs) during operation. The in situ measurements are performed with a micro-AEMFC inserted into a resonator of an electron paramagnetic resonance (EPR) spectrometer, which enables separate monitoring of radicals formed on the anode and cathode sides. The creation of radicals is monitored by the EPR spin trapping technique. For the first time, we clearly show the formation and presence of stable radicals in AEMs during and after long-term AEMFC operation. The main detected adducts during the operation of the micro-AEMFC are DMPO-OOH and DMPO-OH on the cathode side, and DMPO-H on the anode side. These results indicate that oxidative degradation involving radical reactions has to be taken into account when stability of AEMFCs is investigated.

Durability of anion exchange membrane water electrolyzers

“…157,158 Also, hydroxyl (HO ) and hydroperoxyl (HO 2 ) radicals can be produced from the intermediated species of the OER [159][160][161] or cation-site catalyzed reduction of dioxygen. 162,163 Radical induced hydrolysis of polymer electrolytes is expected as hydrogen peroxide is detected in AEMWE cells. 164,165 To evaluate the oxidative stability against radical-induced degradation, Fenton's reagent is commonly employed as a preliminary ex situ accelerated degradation test due to its ability to generate oxygen-containing free radicals in solution.…”

Recent Advances in Electrocatalysts for Alkaline Hydrogen Oxidation Reaction

“…Kruczała and co-workers are the first to prove the formation of stable radicals and short-living radicals during the AEMFCs tests by in situ measurements (Figure 13c). [152] The electron paramagnetic resonance (EPR) spectroscopy was used to quantitatively study stable radicals and the spin trapping technique was used for the determination of the short-living radicals. The results show that the formatted radicals are mainly .OOH and .OH on the cathode side and the H. on the anode side.…”

“…[136] Copyright 2019, ACS; Panel (c): Reproduced with permission. [152] Copyright 2020, ACS; Panels (d, e): Reproduced with permission. [154] Copyright 2020, Nature; Panels (f, g): Reproduced with permission.…”

The joint effect of electrical conductivity and surface oxygen functionalities of carbon supports on the oxygen reduction reaction studied over bare supports and Mn–Co spinel/carbon catalysts in alkaline media

“…However, to make them more widely used, several obstacles must be overcome. As a result, vast-ranging investigations focus on improving the properties of conductive polymer membranes [1][2][3][4][5][6][7] and catalysts for the oxygen reduction reaction (ORR). [8][9][10][11][12][13][14][15] Due to the slow ORR kinetics, which is usually attributed to the high stability of the oxygen molecule, with an OO bond strength of 498 kJ mol −1 , it is necessary to use efficient electrocatalysts to accomplish this process.…”