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

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 mu A cm(ECSA)(-2) 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. (C) 2015 Elsevier B.V. All rights reserved.