Green synthesis of pyrite nanoparticles for energy conversion and storage: a spectroscopic investigation

Pyrite, FeS2, nanoparticles were obtained through a one-pot solvothermal synthesis, without surfactants, carried out at room pressure and mild temperature (?180{\textdegree}C). A thorough characterization of the products was thus performed, including scanning-electron-microscope micromorphology, X-ray diffraction (XRD), diffuse reflectance spectroscopy, and X-ray absorption spectroscopy (both in the XANES and EXAFS regions).Monophasic pyrite products are obtained as aggregates having an approximate dimension of few hundreds of nm. The Scherrer analysis of the Bragg reflections suggests that these aggregates are clusters of smaller units, having a mean size of ~25 nm. The XRD measurements point to a small but significant increase of the Fe{\textendash}S bond distance (+1.7 \%) with respect to reference data. The optical behavior of the pyrite nanoparticles is indistinguishable from that of the bulk pyrite.These results point to the one-pot synthesis as an efficient and {\textquotedblleft}green{\textquotedblright} way of obtaining pyrite nanoparticles exhibiting the same technological properties as bulk pyrite. Indeed these nanoparticles can be considered as a product viable for numerous technological applications in the solar-energy conversion and storage fields.