Controlling morphology and phase of pyrite FeS2 hierarchical particles via the combination of structure-direction and chelating agents

Abstract

Pyrite FeS₂ hierarchical microparticles consisting of cubic-like crystals with well defined {100} faceted cubic textures were successfully synthesized using a simple hydrothermal method with the presence of ethylenediamine (en) and polyvinylpyrrolidone (PVP). The roles of PVP and en in the synthesis process were elucidated by the investigation of morphology and crystalline phases of the products under different reaction conditions and by the analysis of atomic structures of the pyrite (100) and (111) surfaces with different termination layers. While en chelates with Fe²⁺ and reacts with S₈ of the reaction agents to help with dispersion and nucleation as well as the role of reducing agent, PVP acts as both a phase regulator due to its reducing ability and a surface capping agent to bind the iron atoms at the FeS₂ (111) surface and direct the formation of {100} facets. It was found that the oxidation state of iron ions and the species of anions in the iron reagents also played important roles in the formation of crystalline phase and morphology of the products. The pyrite hierarchical microparticles could be utilized as a new semiconductor ink for solution processing of photovoltaic devices and photodetectors as well as cathode materials for lithium batteries.