PtZn alloy nanoparticles with enhanced activity and stability synthesized by a simplified polyol process for electro-oxidation of ammonia

Abstract

This work reports the synthesis of bimetallic alloy PtZn nanoparticles (NPs) using one-pot glycerol-assisted polyol technique in the presence of Pt(acac)2 and Zn(acac)2 for the electrocatalysis of ammonia fuels. Three different compositions of PtnZn/C (n = 1, 2, 3) electrocatalysts are synthesized in which Pt-content is varied with a fixed Zn-content. PtZn NPs are characterized by X-ray diffractometry (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM) for their crystal structures, elemental compositions, and morphological studies. The high-angle annular dark field-scanning TEM-EDS elemental mapping has confirmed that NPs are alloyed with Pt and Zn elements. The electronic structures of alloy NPs are further analyzed by X-ray photoelectron spectroscopy and found a ligand effect resulting in the downshift of d-band center. The incorporation of Zn in NPs decreases the oxygenated species on Pt surface proven by cyclic voltammetry. PtZn NPs are employed for the electrocatalysis of ammonia fuels, namely NH4OH, NH4Cl, NH4NO3, and (NH4)2SO4, where PtZn/C system has shown better electrocatalytic activity than Pt/C. Stability tests are conducted using chronoamperometry for all electrocatalysts of which PtZn/C electrocatalysts have been observed to have good sustainability in the electrochemical environment compared to Pt/C.