A highly reactive precursor in the iron\xa0sulfide system

Adriana Matamoros-Veloza,Liane G Benning,Nora H De Leeuw,Benjamin R G Johnson,Tomasz M Stawski,Umberto Terranova,Oscar Cespedes

doi:10.1038/s41467-018-05493-x

Abstract

Iron sulfur (Fe–S) phases have been implicated in the emergence of life on early Earth due to their catalytic role in the synthesis of prebiotic molecules. Similarly, Fe–S phases are currently of high interest in the development of green catalysts and energy storage. Here we report the synthesis and structure of a nanoparticulate phase (FeSnano) that is a necessary solid-phase precursor to the conventionally assumed initial precipitate in the iron sulfide system, mackinawite. The structure of FeSnano contains tetrahedral iron, which is compensated by monosulfide and polysulfide sulfur species. These together dramatically affect the stability and enhance the reactivity of FeSnano.

Highlights

Iron sulfur (Fe–S) phases have been implicated in the emergence of life on early Earth due to their catalytic role in the synthesis of prebiotic molecules
The existence of solid precursors or intermediates prior to the formation of stable crystals is increasingly established, many experimental and analytical challenges to characterize such entities remain[1]. Evidence for such highly reactive intermediate precursors, frequently structurally different from their bulk counterparts, is available for oxic systems; for example, metastable amorphous phases precede the formation of crystalline CaCO3 polymorphs[2,3], while nanocrystalline phases are necessary precursors for gypsum formation in the CaSO4 system[4,5], and Feoxo Keggin precede the formation of ferrihydrite in the Fe–OH system[6,7]
Using two distinct and highly controlled chemical and fully anaerobic approaches allowed us to quantify all stages in the nucleation, growth, stabilization, and transformations of solid phases in the Fe–S system from aqueous ions to crystalline mackinawite

Summary

Introduction

Iron sulfur (Fe–S) phases have been implicated in the emergence of life on early Earth due to their catalytic role in the synthesis of prebiotic molecules. Despite increasing evidence of the existence of multiple solid precursors in the Fe–S system[1], the nature, structure and stability of early formed solid Fe–S precursors with structures different to that of mackinawite have so far not been documented Such Fe–S phases have been hypothesized as potential membrane catalysts for the formation of prebiotic molecules and life’s emergence on early Earth[14,15,16]. Such reactive Fe–S phases are of prime interest for the potential green catalytic conversion of atmospheric CO216,17, and for the development of sustainable, clean, and low-cost energy storage technologies[18,19]. In anoxic low-temperature environments the formation of pyrite (FeS2) proceeds via this phase through the mackinawite pathway (e.g., mackinawite → greigite (Fe3S4) [ ± → marcasite (FeS2)] and pyrite (FeS2)[9,10,11,20,21,22]

Methods

Results

Conclusion