Electrocatalytic ammonia oxidation on nickel and cobalt nanostructures for efficient hydrogen production

Hydrogen is a promising clean energy alternative, but faces storage and transportation challenges. Ammonia is a viable hydrogen carrier due to its ease of transport and efficient electrochemical decomposition. This study investigates the ammonia oxidation reaction (AOR) over nanostructured nickel and cobalt catalysts on nickel foam (Ni/NF and Co/NF) for low-energy hydrogen production in alkaline conditions. Grand Canonical Density Functional Theory (GC-DFT) reveals ammonia adsorption is thermodynamically favorable on both surfaces, with Ni(111) exhibiting stronger binding. However, Co(111) maintains a slightly smoother kinetic progression through the dehydrogenation steps, resulting in more favorable reaction energetics. Electrochemical measurements confirm Co/NF delivers a high anodic current density of 819 mAcm−2, compared to 522 mAcm−2 for Ni/NF, with a reduced onset potential of ∼0.32 V vs. Ag/AgCl. Co/NF yields superior hydrogen generation with an energy consumption of 4.08 mWhg−1NH₃ and 64.8% cell efficiency, outperforming Ni/NF. This enhanced performance is attributed to favorable kinetics, as Co/NF exhibits a lower Tafel slope and charge transfer resistance. Overall, this combined theoretical and experimental study demonstrates that nanostructured Ni- and Co-modified NF electrodes are efficient, abundant electrocatalysts for sustainable hydrogen production via ammonia electrolysis.