Pt-Decorated highly porous flower-like Ni particles with high mass activity for ammonia electro-oxidation

Pt-Decorated Ni particles with different surface morphologies were directly prepared on a conducting substrate for use as electrocatalysts for ammonia electro-oxidation. The whole preparation process avoided the use of surfactants, binders, and reducing and capping agents. Flower-like Ni particles consisting of interconnected thin nanosheets and featureless Ni particles with a relatively smooth surface were obtained by controlling the electrodeposition potential. Pt-Decorated Ni particles were prepared by the galvanic replacement reaction between Ni particles and Pt2+ ions. The surface morphology and chemical composition of Pt-decorated Ni particles were characterized by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The Pt loading was determined by an inductively coupled plasma method, and the electrocatalytic activity of the prepared electrocatalysts was characterized by cyclic voltammetry. The results showed that there is a significant effect of the surface morphology of Ni particles and the Pt replacement time on the electrocatalytic activity. In particular, Pt-decorated flower-like Ni particles with a highly porous structure exhibited a high mass activity of 75.32 mA mg(-1), which was 2 times higher than that of commercial Pt/C catalysts. The improved activity is attributed not only to the highly porous flower-like morphology, but also to the presence of nanopores and small 2-3 nm sized Pt grains with good dispersion on the petals of flower-like particles.