Synthesis of metal cation doped nanoparticles for single atom alloy catalysts using spontaneous cation exchange

Ion exchange is a chemical reaction in which the ionic components of a solid parent material are exchanged with other ions. It often happens in metal chalcogenide and ionic metal oxide crystals, which are composed of cation and anion constituents. Here, we discovered that the cations in a solution spontaneously exchange with the constituent atoms in metal nanoparticles, forming cation-doped metal nanoparticles. Owing to charge-charge repulsion, the cations are atomically dispersed without aggregating in the nanoparticles that act as single-atom catalysts. The prepared PdRu and PdCe catalysts exhibited remarkable activity for methanol oxidation reaction and hydrogen evolution reaction, in which the Ru and Ce cations serve as active sites. This cation exchange reaction provides a specific tool to synthesize cation single atom catalysts in mild conditions that cannot be obtained via other synthetic methods and will spawn applications like photodynamic therapy, chemical sensing, and devices.