High Metal Loading, Two Nanometer-Sized Platinum Zinc Intermetallic Nanoparticles from Atomically Dispersed Precursors for Hydrogenation Reaction

Ultrafine intermetallic nanoparticles are attractive candidates as catalysts, especially in electrocatalysis and selective hydrogenation reactions. An intermetallic may possess stronger metal bonding and exhibit better chemical stability under harsh reaction conditions than its alloy counterpart, which exists as a solid solution. Thermal treatment is often necessary for the preparation of intermetallic nanoparticles to achieve the required atomic ordering. Such processes are often carried out at elevated temperatures, which inevitably cause particle growth, resulting in a broad distribution in the structure and composition of nanoparticles (NPs). This change poses a challenge in obtaining uniformly deposited, ultrafine intermetallic NPs on supports. Here we report the control over particle size and uniformity of ultrafine PtZn intermetallic NPs using a dual-ligand metal-organic framework (MOF) as atomically dispersed precursors (ADPs) in a one-pot synthesis. Face-centered tetragonal (fct) 2.1 nm sized L1₀-Pt₅₀Zn₅₀ intermetallic NPs were produced after the thermal treatment. The simplicity of this synthesis allows us to study the effects of several key factors on the particle size and uniformity. The resulting catalyst of L1₀-Pt₅₀Zn₅₀ on carbon has a Brunauer-Emmett-Teller (BET) surface area in the order of 150 m²/g. It acts as a highly selective hydrogenation catalyst for the liquid-phase conversion of 1-iodo-4-nitrobenzene and 1-bromo-4-nitrobenzene to the corresponding semihydrogenated products exclusively. Furthermore, the one-pot synthesis using ADPs allows for the preparation of ultrafine (<3 nm) bimetallic nanoparticles with a record high total metal mass loading of 29%, paving a way for the design of high metal loading intermetallic catalysts.