Easy access to Fe ₂ N nanomaterials from Fe nanocrystals and investigation of their electrocatalytic properties for the water electrolysis and CO ₂ reduction

The nanostructured iron nitride phases, comprising only non-toxic and abundant elements, show potential in a wide range of applications, and are thus of great interest in the context of sustainable development. Especially, the nanostructured ε-Fe _<i>x</i> N phase (<i>x</i> = 2-3) can play the role of electrocatalyst (in fuel cells or for hydrogen production), or of anode in Li-ion batteries. However, obtaining morphology and composition (<i>x</i>) controlled nanoparticles of this phase is challenging. Here we show that α-Fe nanoparticles produced by an organometallic approach can be nitridated by a simple exposure to an ammonia flow in mild conditions of temperature, either in the powder form or as thin layers on FTO electrodes while keeping their initial morphology. Structural and magnetic measurements, combined with chemical analysis, and spectroscopic investigations evidenced the formation of the pure ε-Fe₂N phase, with a preserved nanostructure. The electrocatalytic activity of this nanomaterial has been evaluated for CO₂ reduction and for the oxygen evolution reaction. These results may open new perspectives for studying the properties and reactivity of ε-Fe₂N nanomaterials, and promote their use.