Anisotropic Growth of Iron Pyrite FeS₂ Nanocrystals via Oriented Attachment

Pyrite (FeS 2 ) material is attractive for applications in solar cells, lithium batteries, and hydrogen production because of its abundant, nontoxic features as well as the extraordinary electrical and optical properties. Pyrite (FeS 2 ) nanocrystals (NCs) were synthesized via hot injection method, and the crystalline structure and morphologic evolution of pyrite NCs were investigated. We found that pyrite (FeS 2 ) NCs were generated from a mackinawite FeS 0.94 nanosheets template. The initial anisotropic growth of NCs was dominated by oriented attachment mechanism. Ostwald ripening growth became obvious as time progressed, resulting in faceted NCs. In accordance with the analysis of high-resolution transmission electron microscopy (HRTEM) images and surface free energies, we found that the attachment occurs between the opposite facets with high surface free energies including (210)-Fe and (210)-2S as well as (001)-Fe and (001)-2S. The attachment could also happen through a “point-contact” followed by interparticle growth. This study sheds light on a better understanding of the growth mechanism of anisotropic pyrite FeS 2 NCs and provides a means to rationally manipulate the morphology of pyrite FeS 2 NCs in order to achieve desired physical properties for efficient photovoltaic conversions.