Electrochemical performance of Ni–Fe–Co spinel anodes with a nanorod structure in anion exchange membrane water electrolyzers

Abstract

Green hydrogen production via anion exchange membrane water electrolyzers (AEMWEs) is becoming a game changer as a sustainable energy solution by offering a cost-effective alternative to conventional electrolyzers. In this study, Ni–Fe–Co spinel electrocatalysts, with a specific nanorod morphology engineered to optimize ion diffusion, were synthesized via a sono-hydrothermal method and evaluated as anodes in AEMWEs. Four different compositions of nanostructured Ni–Fe–Co oxides, all based on the NiCo₂O₄ spinel, and named NiCo3–S, NiCo4–S, NiFe1–S (10 % Fe), and NiFe2–S (20 % Fe) were synthesized and spray-coated onto nickel felt gas diffusion layers. A Pt/C cathode and an Aemion + membrane completed the 5 cm² AEMWE assembly. The structural analysis confirmed well-defined spinel phases and a nanorod morphology for all the electrocatalysts, with NiFe2–S exhibiting enhanced crystallinity and smaller nanorod dimensions. Electrochemical tests revealed that AEM cells equipped with NiFe2–S anodes achieved a low cell voltage of 1.808 V at 1 A. cm⁻² and 2.06 V at 2 A. cm⁻², outperforming other electrocatalysts. A 45-h DC stability test showed only a slight voltage increase (1.815 V–1.866 V), while a 20-h accelerated stress test (AST) confirmed minimal degradation. These results demonstrate that Fe incorporation inside an already optimized nanorod structure improves electrocatalytic activity, charge transfer, and durability, making NiFe2–S a promising anode material for scalable AEMWE applications, further advancing the development of cost-effective green hydrogen production.