title: Improvement of catalytic water oxidation on MnOx films by heat treatment.
abstract: Manganese oxides (MnOx ) are considered to be promising catalysts for water oxidation. Electrodeposited MnOx 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 MnOx 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.
authors: ARC Centre of Excellence for Electromaterials Science, School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
authors: Fengling
authors: F
authors: Zhou
authors: Alex
authors: A
authors: Izgorodin
authors: Rosalie K
authors: RK
authors: Hocking
authors: Vanessa
authors: V
authors: Armel
authors: Leone
authors: L
authors: Spiccia
authors: Douglas R
authors: DR
authors: Macfarlane
mesh_terms: D002384:Catalysis; D006358:Hot Temperature; D017895:Manganese Compounds / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D014867:Water / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy; D014961:X-Ray Diffraction
chemical_list: D017895:Manganese Compounds; D010087:Oxides; D014867:Water; C027424:manganese oxide