A facile synthesis of ternary PtCuNi nanoalloys as catalysts for the hydrogen evolution and oxygen evolution reactions both in alkaline and acidic media

Abstract

Ternary PtCuNi nanoalloys with different Pt/Cu/Ni ratios were synthesized by using one-pot modified polyol method, and their electrocatalytic performance in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) was investigated in detail. The structural analysis of as-synthesized PtCuNi nanoalloys performed by using Rietveld refinement and X-ray diffraction (XRD) analyses confirmed that they have the cubic crystal phase with a space group of the face-centered cubic (fcc)-Fm3<overline>\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{3 }$$\end{document}m, where the increasing Pt ratio increased the lattice parameter to 3.712 & Aring; and decreased the crystal size to 1.59 +/- 0.39 nm. All prepared nanoalloys showed a uniform spherical shape with an average particle size between 3 and 9 nm. The Pt58Cu15Ni27 nanocatalyst with an average particle size of 3.62 nm shows that lowest Tafel slopes of 40 and 62 mV dec-1 for HER region both in alkaline and acidic media, respectively. Chronoamperometry tests of Pt58Cu15Ni27 nanocatalysts were performed at -0.3 mV (vs. RHE) in both acidic and alkaline solution displayed that they all exhibited excellent cycle stability. The Pt58Cu15Ni27 nanocatalysts also exhibited the lowest overpotentials (eta) at 10 mA cm-2 of 1.36 V for OER in alkaline solution, while the Pt9Cu39Ni52 demonstrated the lowest Tafel slopes of 30 and 44 mV dec-1 for OER in both alkaline and acidic media, respectively. The enhanced electrocatalytic activity of the PtCuNi nanocatalysts is attributed to the stabilization of Pt through electron transfer from Cu and Ni in both reaction media, as well as their critical role in facilitating the cleavage of HO-H bonds during water splitting.