An Atomic‐Scale View at γ’‐Fe4N as Hydrogen Barrier Material

Hydrogen, while a promising sustainable energy carrier, presents challenges such as the embrittlement of materials due to its ability to penetrate and weaken their crystal structures. Here γ’‐Fe4N nitride layers, formed on iron through a cost‐effective gas nitriding, are investigated as an effective hydrogen permeation barrier. The relatively short process carried out at 570 °C consisted of pre‐nitriding in an atmosphere with higher nitriding potential, followed by treatment in a nitriding potential of 0.0016 Pa−1/2 to obtain a pure γ’ layer. A combination of screening methods, including atom probe tomography, density functional theory calculations, and hydrogen permeation analysis, revealed that the nitride layer reduces hydrogen diffusion (steady‐state hydrogen flux 3.21 x 10−8 mol/m2·s) by a factor of 20 compared to pure iron, at room temperature. This reduction is achieved by creating energetically unfavorable states due to stronger hydrogen‐binding at the surface and high energy barriers for diffusion. The findings demonstrate the potential of γ’‐Fe4N as a cost‐efficient and easy‐to‐process solution to protect metallic materials exposed to hydrogen at low temperatures, with great advantages for large‐scale applications.