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Improvement of Catalytic Water Oxidation on MnO x Films by Heat Treatment
Author(s) -
Zhou Fengling,
Izgorodin Alex,
Hocking Rosalie K.,
Armel Vanessa,
Spiccia Leone,
MacFarlane Douglas R.
Publication year - 2013
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201200849
Subject(s) - catalysis , aqueous solution , raman spectroscopy , inorganic chemistry , manganese , x ray absorption spectroscopy , electrolyte , chemical engineering , fourier transform infrared spectroscopy , microstructure , thermal treatment , catalytic oxidation , chemistry , materials science , absorption spectroscopy , metallurgy , organic chemistry , electrode , physics , quantum mechanics , optics , composite material , engineering
Manganese oxides (MnO x ) are considered to be promising catalysts for water oxidation. Electrodeposited MnO x films from aqueous electrolytes have previously been shown to exhibit a lower catalytic action than films deposited from ionic liquids when tested in strongly alkaline conditions. In this study, we describe a thermal treatment that converts the MnO x films deposited from aqueous electrolytes to highly catalytic films with comparable activity to ionic‐liquid‐deposited films. The films deposited from aqueous electrolytes show a remarkable improvement in the catalysis of water oxidation after heat treatment at a low temperature (≤120 °C) for 30 min. The films were characterised by using XRD and SEM, and energy‐dispersive X‐ray (EDX), FTIR and Raman spectroscopy, which indicate that dehydration occurs during the heat treatment without significant change to the microstructure or bulk composition. The X‐ray absorption spectroscopy (XAS) results show the growth of small amounts (ca. 3–10 %) of reduced Mn species (Mn II or Mn III ) after heat treatment. The dehydration process removes structural water and hydroxyl species to result in a conductivity improvement and a more active catalyst, thereby contributing to the enhancement in water oxidation performance.