Exploring AlFe3N and GaFe3N as nitrogen carriers for chemical looping ammonia synthesis via density functional theory

The urgent demand for sustainable ammonia production has motivated the exploration of alternatives to the energy-intensive Haber–Bosch process. In this study, density functional theory (DFT) calculations were employed to evaluate the catalytic performance of iron-based antiperovskite nitrides, AlFe₃N and GaFe₃N, for green ammonia synthesis via chemical looping. Stability analyses, including phonon dispersion, AIMD simulations, and elastic constants, confirm the dynamic, thermal, and mechanical robustness of both materials. Electronic structure results reveal metallic and ferromagnetic behavior, with a weaker Fe–N bond in GaFe₃N due to the higher electronegativity of Ga, which enhances charge transfer and surface reactivity. Thermodynamic calculations show that both hydrogenation and (nitridation) are spontaneous at low temperatures, with negative Gibbs free energy values up to 248 K for AlFe₃N and 415 K for GaFe₃N. Surface analysis identifies the (111) facet as the most reactive, where Ga-based nitride demonstrates stronger H₂ adsorption (-3.828 eV) and a more exothermic nitrogen vacancy formation energy (-2.429 eV) than Al-based nitride, while the latter shows slightly stronger N₂ adsorption (-1.405 eV). The associative Mars–van Krevelen mechanism is energetically more favorable for GaFe₃N, confirming its enhanced catalytic performance. These findings highlight the critical role of material composition in tuning catalytic behavior and establish AlFe₃N and GaFe₃N as promising catalysts for low-temperature, sustainable ammonia synthesis. Looking ahead, the integration of high-throughput screening with machine learning is expected to accelerate the discovery of efficient nitride-based catalysts for green ammonia production.