Сибирский федеральный университет

Тип публикации: статья из журнала

Год издания: 2017

Идентификатор DOI: 10.1039/c6cp07598c

Ключевые слова: transition-metal sulfides, ANGULAR-DISTRIBUTION PARAMETERS, RANGE 100-5000 EV, Electronic-structure, K-edge, electrochemical oxidation, energy, Xps, dissolution, pyrite

Аннотация: The depletion of oxidized metal sulfide surfaces in metals due to the preferential release of cations is a common, but as yet poorly understood phenomenon. Herein, X-ray photoelectron spectroscopy using excitation energies from 1.25 keV to 6 keV, and Fe K-and S K-edge X-ray absorption near-edge spectra in total electron and partial fluorescence yield modes was employed to study natural chalcopyrite oxidized in air and etched in an acidic ferric sulfate solution. The metal-depleted undersurface formed was found to consist of a thin, 1-4 nm, outer layer containing polysulfide species, a layer with a pronounced deficiency of metals, mainly iron, and an abundant disulfide content but negligible polysulfide content (about 20 nm thick after the chemical etching), and a defective underlayer which extended down to about a hundred nm. DFT+U was used to simulate chalcopyrite with increasing numbers of removed Fe atoms. It was found that the structure with disulfide anion near double Fe vacancies, and the 'defective' structure comprising Cu in the position of Fe and Cu vacancy are most energetically favorable, especially when using a higher Hubbard-type parameter U, and have a large density of states at the Fermi level, whereas polysulfide anions are stable only near the surface. We propose a mechanism explaining the formation of the layered undersurface and 'passivation' of metal sulfides by (i) arrested decomposition of a nearly stoichiometric sulfide surface, and (ii) faster interfacial transfer and solid diffusion of cations towards the surface; (iii) stability limits for specific defect structures, promoting their expansion in depth rather than through compositional changes, excluding surface layers; (iv) decay of surface polysulfide layer yielding elemental sulfur.

Журнал: PCCP: Physical Chemistry Chemical Physics

Выпуск журнала: Т. 19, № 4

Номера страниц: 2749-2759

ISSN журнала: 14639076

Издатель: Royal Society of Chemistry

• Mikhlin Yuri (Russian Acad Sci, Inst Chem & Chem Technol, Siberian Branch, 50-24 Krasnoyarsk, Krasnoyarsk 660036, Russia)
• Nasluzov Vladimir (Russian Acad Sci, Inst Chem & Chem Technol, Siberian Branch, 50-24 Krasnoyarsk, Krasnoyarsk 660036, Russia)
• Romanchenko Alexander (Russian Acad Sci, Inst Chem & Chem Technol, Siberian Branch, 50-24 Krasnoyarsk, Krasnoyarsk 660036, Russia)
• Tomashevich Yevgeny (Russian Acad Sci, Inst Chem & Chem Technol, Siberian Branch, 50-24 Krasnoyarsk, Krasnoyarsk 660036, Russia)
• Shor Alexey (Russian Acad Sci, Inst Chem & Chem Technol, Siberian Branch, 50-24 Krasnoyarsk, Krasnoyarsk 660036, Russia)
• Félix Roberto (Helmholtz Zentrum Berlin Mat & Energie GmbH, Renewable Energy, Lise Meitner Campus,Hahn Meitner Pl 1, D-14109 Berlin, Germany)

• Ядро РИНЦ (eLIBRARY.RU)