CoOx thin film deposited by CVD as efficient water oxidation catalyst: change of oxidation state in XPS and its correlation to electrochemical activity
| Autor: | Sarina Paulus, Sascha Hoch, Artjom Maljusch, Carolin Wittich, Joachim Klett, Wolfram Jaegermann, Patrick Stenner, Natascha Weidler, Joachim Brötz, Jona Schuch, Bernhard Kaiser |
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| Rok vydání: | 2016 |
| Předmět: |
Inorganic chemistry
Oxygen evolution Oxide General Physics and Astronomy Nanotechnology 02 engineering and technology Overpotential 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences chemistry.chemical_compound X-ray photoelectron spectroscopy chemistry Catalytic oxidation Plasma-enhanced chemical vapor deposition Oxidation state Physical and Theoretical Chemistry Thin film 0210 nano-technology |
| Zdroj: | Physical Chemistry Chemical Physics. 18:10708-10718 |
| ISSN: | 1463-9084 1463-9076 |
| DOI: | 10.1039/c5cp05691h |
| Popis: | To reduce energy losses in water electrolysers a fundamental understanding of the water oxidation reaction steps is necessary to design efficient oxygen evolution catalysts. Here we present CoOx/Ti electrocatalytic films deposited by thermal and plasma enhanced chemical vapor deposition (CVD) onto titanium substrates. We report electrochemical (EC), photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) measurements. The electrochemical behavior of the samples was correlated with the chemical and electronic structure by recording XPS spectra before and after each electrochemical treatment (conditioning and cyclovoltammetry). The results show that the electrochemical behavior of CoOx/Ti strongly depends on the resulting electronic structure and composition. The thermal deposition leads to the formation of a pure Co(II)Ox which transforms to a mixed Co(II)Co(III)Ox during the OER. This change in oxidation state is coupled with a decrease in overpotential from η = 0.57 V to η = 0.43 V at 5 mA cm(-2). Plasma deposition in oxygen leads to a Co(III)-dominated mixed CoOx, that has a lower onset potential as deposited due to a higher Co(III) content in the initial deposited material. After the OER XPS results of the CoOx/Ti indicate a partial formation of hydroxides and oxyhydroxides on the oxide surface. Finally the plasma deposition in air, results in a CoOxOH2 surface, that is able to completely oxidizes during OER to an oxyhydroxide Co(III)OOH. With the in situ formed CoOOH we present a highly active catalyst for the OER (η = 0.34 at 5 mA cm(-2); η = 0.37 V at 10 mA cm(-2)). |
| Databáze: | OpenAIRE |
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