Novel Solid-State Synthesis of Platinum-Alloy Nanoparticles via Uniform Decomposition of Bimetallic Compounds on Carbon

Among various types of alloy nanomaterials, Pt-based alloys have been intensively investigated to advance different fields of catalysis, especially electrochemical oxygen reduction reaction (ORR). ORR electrocatalysis is a primary bottleneck to the practical applications of fuel cell systems that mainly utilize hydrogen and oxygen gas to generate electricity and pure water. In recent decades, tremendous attention has been paid on alloying different kinds of transition metal species with platinum. However, the preparation of active and durable Pt-alloy catalysts in an economically viable way is still challenging. Therefore, alternative approaches to achieve facile synthesis of highly active alloy nanostructures on carbon supports with high loading are highly desirable. Due to the simplicity and scalability, the direct synthesis of alloy nanoparticles on carbon supports promises its industrial applications with economic processing costs. However, controlling the alloying of two different metal precursors on carbon surfaces is highly challenging, let alone any attempt for high-loading-synthesis.<br/>Here, we designed a straightforward approach that can achieve highly loaded and uniformly alloyed bimetallic nanoparticles on carbon supports. Electrostatic interaction between a cationic metal complex and an anionic metal complex is essential for the preparation of a bimetallic compound (MPt compound, [M(bpy)₃][PtCl₆], M = Fe, Co, Ni, bpy = 2,2’-bipyridine) containing an equal amount of two constituent metals. The sub-micrometer-sized bimetallic compound grains can be readily attached onto carbon supports, such as graphene oxide, which are then thermally decomposed to spread a large amount of metal precursor uniformly on the surface of carbon. Notably, we observed a significantly high degree of atomic ordering in L1₀-FePt nanoparticles after annealing at 700 °C as confirmed by XRD, magnetic hysteresis, and HAADF-STEM measurements. This study may inspire future efforts on designed synthesis of multimetallic precursors that can thermally decompose on supports, providing uniformly alloyed nanoparticles or other forms of nanostructured alloys.<br/><br/><b>Reference</b>: T. Y. Yoo et al. <i>J. Am. Chem. Soc.</i> <b>2020</b>, 142, 33, 14190–14200.