Atomic-scaled surface engineering Ni-Pt nanoalloys towards enhanced catalytic efficiency for methanol oxidation reaction

Surface engineering is known as an effective strategy to enhance the catalytic properties of Pt-based nanomaterials. Herein, we report on surface engineering Ni-Pt nanoalloys with a facile method by varying the Ni doping concentration and oleylamine/oleic- acid surfactant-mix. The alloy-composition, exposed facet condition, and surface lattice strain are, thereby manipulated to optimize the catalytic efficiency of such nanoalloys for methanol oxidation reaction (MOR). Exemplary nanoalloys including Ni_0.69Pt_0.31 truncated octahedrons, Ni_0.45Pt_0.55 nanomultipods and Ni_0.20Pt_0.80 nanoflowers are thoroughly characterized, with a commercial Pt/C catalyst as a common benchmark. Their variations in MOR catalytic efficiency are significant: 2.2 A/mg_Pt for Ni_0.20Pt_0.80 nanoflowers, 1.2 A/mg_Pt for Ni_0.45Pt_0.55 nanomultipods, 0.7 A/mg_Pt for Ni_0.69Pt_0.31 truncated octahedrons, and 0.6 A/mg_Pt for the commercial Pt/C catalysts. Assisted by density functional theory calculations, we correlate these observed catalysis-variations particularly to the intriguing presence of surface interplanar-strains, such as {111} facets with an interplanar-tensile-strain of 2.6% and {200} facets with an interplanar-tensile-strain of 3.5%, on the Ni_0.20Pt_0.80 nanoflowers.