title: Quasi-in-situ single-grain photoelectron microspectroscopy of Co/PPy nanocomposites under oxygen reduction reaction.
abstract: This paper reports an investigation into the aging of pyrolyzed cobalt/polypyrrole (Co/PPy) oxygen reduction reaction (ORR) electrocatalysts, based on quasi-in-situ photoelectron microspectroscopy. The catalyst precursor was prepared by potentiostatic reverse-pulse coelectrodeposition from an acetonitrile solution on graphite. Accelerated aging was obtained by quasi-in-situ voltammetric cycling in an acidic electrolyte. Using photoelectron imaging and microspectroscopy of single Co/PPy grains at a resolution of 100 nm, we tracked the ORR-induced changes in the morphology and chemical state of the pristine material, consisting of uniformly distributed ∼20 nm nanoparticles, initially consisting of a mixture of Co(II) and Co(III) oxidation states in almost equal amounts. The evolution of the Co 2p, O 1s, and N 1s spectra revealed that the main effects of aging are a gradual loss of the Co present at the surface and the reduction of Co(III) to Co(II), accompanied by the emergence and growth of a N 1s signal, corresponding to electrocatalytically active C-N sites.
authors.affiliation: Dipartimento di Ingegneria dell'Innovazione, Università del Salento , via Monteroni, 73100 Lecce, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Bocchetta
authors.forename: Matteo
authors.initials: M
authors.lastname: Amati
authors.forename: Benedetto
authors.initials: B
authors.lastname: Bozzini
authors.forename: Massimo
authors.initials: M
authors.lastname: Catalano
authors.forename: Alessandra
authors.initials: A
authors.lastname: Gianoncelli
authors.forename: Luca
authors.initials: L
authors.lastname: Gregoratti
authors.forename: Antonietta
authors.initials: A
authors.lastname: Taurino
authors.forename: Maya
authors.initials: M
authors.lastname: Kiskinova
keywords: X-ray photoelectron spectroscopy; cobalt; electrocatalyst; nanocomposites; oxygen reduction; photoelectron microscopy; polypyrrole