A core-shell NiCu@NiCuOOH 3D electrode induced by surface electrochemical reconstruction for the ammonia oxidation reaction

A direct ammonia microfluidic fuel cell is a potential portable carbon-free clean energy device. In this work, a NiCu-based core-shell 3D electrode is obtained by electrodeposition and surface electrochemical reconstruction on the nickel foam substrate. The physical characterization results confirm the core-shell structure with NiCu as the core and Cu(OH)2 and NiOOH as the shell. In the 3D electrode, the metal core continuously transfers charge to the surface to transform into active species (NiCu hydroxides), thus accelerating the slow ammonia oxidation reaction kinetics. Furthermore, the 3D porous structure is conducive to the rapid diffusion and transport of ions, which effectively improves the fuel depletion boundary layer problem. Consequently, electrochemical tests indicate that the [email protected] electrode show excellent ammonia oxidation reaction activity and good stability, reaching a maximum current density of 90 mA cm−2 at the potential of 0.7 V vs. saturated calomel electrode (SCE). When 2 M NaOH + 3 M NH4Cl is adopted as fuel for the DAMFC, an open circuit voltage of 0.72 V and a peak power density of 17.1 mW cm−2 can be obtained, while the limiting current density is as high as 102 mA cm−2.