Synthesis of Pt-Rare Earth Metal Nanoalloys

Chemical synthesis of platinum-rare earth metal (Pt-RE) nanoalloys, one of the most active catalysts for the oxygen reduction reaction, has been a formidable challenge, mainly due to the vastly different standard reduction potentials of the two metals and high oxophilicity of the latter. Here we report a universal chemical process to prepare Pt-RE nanoalloys with tunable compositions and particle sizes. Pt and RE metal ions from the most common hydrated metal salts are first atomically embedded into an in situ formed C-N network, yielding a stable compound insensitive to O₂ and H₂O. The Pt-RE nanoalloys are subsequently obtained by heating the compound under a mild reducing atmosphere (e.g., 3.3% H₂/Ar). The key intermediate step of the process is the formation of RE carbodiimides (RE₂(CN₂)₃) along with Pt particles. This synthesis mechanism suggests an efficient strategy to prepare nanoalloys with highly reactive metals.