Electrochemical oxidation of ammonia by multi-wall-carbon-nanotube-supported Pt shell–Ir core nanoparticles synthesized by an improved Cu short circuit deposition method

•MWCNT-supported Pt shell–Ir core nanoparticles were synthesized by ICSCD method.•The overpotential of Pt/Ir/MWCNT for ammonia oxidation (AOX) was the lowest.•Kinetic analysis for AOX were performed using Runge–Kutta and Gauss–Newton methods.•The change of the electronic states in the Pt 4f orbit of the Pt/Ir/MWCNT was observed.

Multi-wall-carbon-nanotube (MWCNT)-supported Pt shell–Ir core (Pt/Ir/MWCNT) nanoparticles were synthesized by an improved Cu short circuit deposition (ICSCD) method and were characterized by thermogravimetry (TG), transmission electron microscope (TEM), X-ray diffractometry (XRD), X-ray photon spectroscopy (XPS), and electrochemical measurements for ammonia oxidation catalysis activity. It was revealed that the overvoltage for the ammonia oxidation of Pt/Ir/MWCNT (0.52 V) at 1 μA cm− 2ECSA is lower than those of Pt/MWCNT (0.55 V). The activation energies of the catalysis toward ammonia electrooxidation were estimated as 28.2 kJ (Pt/MWCNT), 27.8 kJ (Ir/MWCNT) and 33.6 kJ (Pt/Ir/MWCNT) at 0.60 V vs. RHE in 100 mM NH3–0.1 M KOH. On the basis of computational kinetic analysis of the chronoamperometric curves in ammonia solution, it was revealed that the apparent rate constant of ammonia oxidation of Pt/Ir/MWCNT is higher than that of Pt/MWCNT, suggesting that the electronic property of Pt was affected by the Ir core atoms.