Abiotic transformations of nitrogen mediated by iron sulfides and related species from early Earth to catalyst design

Abstract

Nitrogen fixation and the cycles of nitrogen on Earth are key to life as we know it and are critical to both modern agriculture and sustaining natural ecosystems. Despite its importance, there is still much we do not know about the processes of transforming nitrogen in natural systems. Nitrogen transformation into ammonia is fundamentally a chemical reduction reaction. It can occur catalytically where there is a source of electrons and a catalyst, or directly where a substrate is concomitantly oxidized, providing the source of electrons directly. In this review we explore the chemistry of iron sulfides to understand the reactions they mediate when they interact with nitrogen species, both as direct reductants and as catalysts, as well as the relationship between catalysis and reduction. In parallel it also describes the chemistry of Earth from a protoplanet through to modern times of relevance to understanding nitrogen speciation and historical drivers of these transformations, with a focus on how the pressures and temperatures on Earth may have impacted nitrogen, iron, sulfur and related species. We explore how iron sulfides can both directly and catalytically mediate some chemical reduction reactions and explore how this may have been significant in life's origins.