Origin of the heat-induced improvement of catalytic activity and stability of MnOx electrocatalysts for water oxidation

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Abrashev, Miroslav V.Univ Sofia St Kliment Ohridski, Fac Phys, Sofia 1164, Bulgaria (författare)

Origin of the heat-induced improvement of catalytic activity and stability of MnOx electrocatalysts for water oxidation

Artikel/kapitelEngelska2019

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2019
ROYAL SOC CHEMISTRY,2019
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LIBRIS-ID:oai:DiVA.org:uu-391360
https://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-391360URI
https://doi.org/10.1039/c9ta05108bDOI

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Språk:engelska
Sammanfattning på:engelska

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Catalysis of the oxygen evolution reaction (OER) by earth-abundant materials in the near-neutral pH regime is of great interest as it is the key reaction for non-fossil fuel production. To address the pertinent stability problems and insufficiently understood structure-activity relations, we investigate the influence of moderate annealing (100-300 degrees C for 20 min) for two types of electrodeposited Mn oxide films with contrasting properties. Upon annealing, the originally inactive and structurally well-ordered Oxide 1 of birnessite type became as OER active as the non-heated Oxide 2, which has a highly disordered atomic structure. Oxide 2 also improved its activity upon heating, but more important is the stability improvement: the operation time increased by about two orders of magnitude (in 0.1 M KPi at pH 7). Aiming at atomistic understanding, electrochemical methods including quantitative analysis of impedance spectra, X-ray spectroscopy (XANES and EXAFS), and adapted optical spectroscopies (infrared, UV-vis and Raman) identified structure-reactivity relations. Oxide structures featuring both di-mu-oxo bridged Mn ions and (close to) linear mono-mu-oxo Mn3+-O-Mn4+ connectivity seem to be a prerequisite for OER activity. The latter motif likely stabilizes Mn3+ ions at higher potentials and promotes electron/hole hopping, a feature related to electrical conductivity and reflected in the strongly accelerated rates of Mn oxidation and O-2 formation. Poor charge mobility, which may result from a low level of Mn3+ ions at high potentials, likely promotes inactivation after prolonged operation. Oxide structures related to the perovskite-like zeta-Mn2O3 were formed after the heating of Oxide 2 and could favour stabilization of Mn ions in oxidation states lower than +4. This rare phase was previously found only at high pressure (20 GPa) and temperature (1200 degrees C) and this is the first report where it was stable under ambient conditions.

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NATURVETENSKAP Kemi Materialkemi hsv//swe
NATURAL SCIENCES Chemical Sciences Materials Chemistry hsv//eng

Biuppslag (personer, institutioner, konferenser, titlar ...)

Chernev, PetkoUppsala universitet,Molekylär biomimetik,Free Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany(Swepub:uu)petch350 (författare)
Kubella, PaulFree Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany (författare)
Mohammadi, Mohammad RezaFree Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany;Univ Sistan & Baluchestan, Dept Phys, Zahedan 9816745845, Iran (författare)
Pasquini, ChiaraFree Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany (författare)
Dau, HolgerFree Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany (författare)
Zaharieva, IvelinaFree Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany (författare)
Univ Sofia St Kliment Ohridski, Fac Phys, Sofia 1164, BulgariaMolekylär biomimetik (creator_code:org_t)

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Ingår i:Journal of Materials Chemistry A: ROYAL SOC CHEMISTRY7:28, s. 17022-170362050-74882050-7496

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Av författaren/redakt...: Abrashev, Mirosl ...; Chernev, Petko; Kubella, Paul; Mohammadi, Moham ...; Pasquini, Chiara; Dau, Holger; visa fler...; Zaharieva, Iveli ...; visa färre...

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