Synthesis of Ni–Pd nanocubes and nanorods with high selectivity through a modified polyol process

• Use of solvated bromide ions enabled synthesis of shape-controlled nanoparticles.
• Size of the nanocubes was not affected by TTAB-to-precursor ratio.
• Shape distributions of nanoparticles were affected by bromide ion concentration.
• Pd and Ni concentrations were homogeneous within the nanoparticles.

Shape controlled bimetallic nanoparticles are important for catalytic, electrocatalytic, optical, and magnetic applications. This effort describes the synthesis of monodisperse bimetallic nickel–palladium (Ni0.25Pd0.75) nanocubes and nanorods with a combined shape selectivity of over 85%. Composition of the synthesized nanoparticles was determined using STEM-EDX and XRD. The shape control was achieved through the use of poly-vinyl pyrrolidone (PVP) surfactant and solvated bromide ions in 1,5-propanediol under an inert argon atmosphere. The use of bromide ions facilitated the stabilization of (1 0 0) and (1 1 0) surface facets, yielding nanocubes and nanorods, respectively, while the polymeric capping agent prevented agglomeration. The influence of the bromide ions was verified by using TEM imaging to ascertain the shapes of the synthesized nanoparticles. The reduction temperature used in the synthesis (140 °C to 180 °C) and the bromide ion-to-metal precursor ratio (15:1 to 50:1) were varied to maximize the shape distribution towards nanocubes and nanorods and to regulate the nucleation and growth phases of the synthesis.