Electrocatalysis of Oxygen Reduction on Polypyrrole/Mixed Valence Spinel Oxide Nanoparticles

Abstract

Composite electrodes based on mixed valence oxide nanoparticles ͑Ox͒ embedded in an electrically conductive polymer ͑ECP͒ were investigated toward the oxygen reduction reaction ͑ORR͒. ECP was polypyrrole ͑PPy͒, and Ox was the spinel mixed valence oxide Cu 1.4 Mn 1.6 O 4 , which is known to be an electrocatalyst of the ORR in neutral and alkaline media. The main findings were that in such a composite electrode ͑i͒ the spinel lattice and the electrocatalytic activity of the oxide remained remarkably stable in acidic media where normally this oxide would be electrochemically reduced, and ͑ii͒ PPy retained its electrical conductivity at cathodic potentials where it would be normally in its insulating reduced state. Those composite electrodes sustained the ORR for hours without signs of deterioration.

Oxygen reduction on high-area carbon cloth-supported oxide nanoparticles/polypyrrole composite electrodes

“…In subsequent publications [24][25][26], we have confirmed the feasibility for the ORR of multilayer composite electrodes having the structure GC/ PPy/PPy(Ox)/PPy (GC, glassy carbon; PPy, polypyrrole; Ox, oxide), Ox being a spinel oxide of copper and manganese, Cu 1.4 Mn 1.6 O 4 or nickel and cobalt, Ni 0.3 Co 2.7 O 4 . In the composite electrode, nanoparticles of the electrocatalyst, Ox, were sandwiched between two PPy layers.…”

“…If the same procedures was adopted to prepare the composite electrode as in our previously publications [23][24][25][26], much less quantity of the oxide can be involved in the polymer matrix due to the blocking of CC porous structures by first PPy layer and the very limited solubility of the oxide. In this case, therefore, directly pipetting the oxide dispersion solution onto CC was used as described in the experimental section.…”

“…Cu 1.4 Mn 1.6 O 4 mixed valence oxide particles were prepared by thermal decomposition of coprecipitated hydroxides, as reported before [23][24][25][26]. Briefly, an excess quantity of NaOH (pellets, Aldrich, 99.99%) was slowly added to a mixed solution of MnSO 4 ·H 2 O + CuSO 4 (Aldrich, 98%) in stoichiometric proportions.…”

“…In the composite electrode, nanoparticles of the electrocatalyst, Ox, were sandwiched between two PPy layers. The external PPy layer has a protective role that resulted in the possibility of its application in neutral and acidic electrolytes [24][25][26]. To illustrate the achievement of a high current density for ORR with Cu 1.4 Mn 1.6 O 4 oxide nanoparticles as electrocatalyst, which is very important in battery and wastewater treatment applications, in this report we construct specifically a high-area tridimensional electrode based on carbon cloth (CC) with the oxide sandwiched between CC fiber backbone and PPy layer.…”

Highly methanol-tolerant non-precious metal cathode catalysts for direct methanol fuel cell

“…To date, non-PGM cathode catalysis research has focused on three main groups of compounds with particularly good promise: inorganic oxides [4][5][6], metal selenides [7,8], and pyrolyzed N 4 -transition metal macrocycles and N 4 -metal chelates of Fe or Co [9][10][11][12]. Several groups showed that templated CoTMPP-based ORR catalysts, supported on various carbon or silica templates and then heat-treated, are active in oxygen reduction but not methanol oxidation [9][10][11][12].…”