Abstract
Nanocubic pyrite (FeS2) crystals with exposed (100) crystal faces and sizes of 100–200 nm were successfully synthesized via a facile hydrothermal method using greigite (Fe3S4) as the iron precursor and thiourea (NH2CSNH2) as the sulfur source. When the concentration of thiourea was 40 mmol/L, both pyrite and hematite were observed in the as-prepared sample, indicating incomplete conversion of greigite into pyrite. With an increased thiourea concentration to 80 mmol/L, pyrite was found to be the only crystalline phase in the synthesized samples. All greigite could be transformed to pyrite within 24 h via the hydrothermal method, while further prolonging the hydrothermal time had insignificant effect on the crystal phase composition, crystallinity, and morphologies of the prepared nanocubic pyrite crystals. In contrast, when a mixture of Na2S and S powder was used to replace the thiourea as the sulfur source, tetragonal, orthorhombic, cubic, and irregular pyrite crystal particles with sizes of 100 nm–1 μm were found to co-exist in the prepared samples. These results demonstrate the critical influence of sulfur source on pyrite morphology. Furthermore, our hydrothermal process, using a combination of greigite and thiourea, is proved to be effective in preparing nanocubic pyrite crystals. Our findings can also provide new insight into the formation environments and pathways of nanocubic pyrite under hydrothermal conditions.
Highlights
Iron sulfides, pyrite (FeS2 ), are ubiquitous in various hydrothermal ore deposits as well as Earth surface environments, and their scientific merits have been demonstrated in many fundamental studies
To further investigate the influence of the type of sulfur source on the synthesis of pyrite, a mixture of Na2 S and S powder was used as the sulfur source to react with greigite precursor
Nanocubic pyrite crystals with exposed (100) crystal faces and edge lengths of approximately 100–200 nm were fabricated via a facile hydrothermal method with greigite as the iron precursor and thiourea as the sulfur source
Summary
Pyrite (FeS2 ), are ubiquitous in various hydrothermal ore deposits as well as Earth surface environments, and their scientific merits have been demonstrated in many fundamental studies. Thanks to its high optical absorption coefficient, unique electrical and semiconducting properties, and suitable band gap (0.95 eV), pyrite (especially micro-nanopyrite) has received extensive attention for its potential applications in electrocatalytic hydrogen evolution reactions (HERs), catalytic hydrogenation, high capacity lithium ion batteries, photovoltaics, photocatalysts, photoelectrochemical solar cells, and so on [16,17,18,19]. It should be noted the chemical composition (or purity), size, morphology, exposed surface facet, and microstructure can significantly affect the surface physiochemical properties of pyrite, and impact its application performance [3]. Synthesis of pure-phase pyrite with controllable morphology and specific facets is of great significance for their application and, has attracted considerable research interest in recent years
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