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.

Multi-metallic Pd@FePt core–shell nanoparticles were synthesized using a direct seed-mediated growth method, consisting of facile and mild procedures, to increase yield. The Fe/Pt ratio in the shell was easily controlled by adjusting the amount of Fe and Pt precursors. Furthermore, compared with commercial Pt/C catalysts, Pd@FePt nanoparticles exhibited excellent activity and stability toward the methanol oxidation reaction (MOR), making them efficient in direct methanol fuel cells (DMFC).

The synthesis of Pd@Pt core–shell nanocubes was achieved through a direct seed-mediated growth method. This process represents a simple and cost-effective way to produce core–shell nanocubes. The morphology of the Pd@Pt core–shell nanocubes varied from simple cubic to concave cubic, depending on the reducing agent and the Pt content. The selection of the reducing agent is important because the reduction rate is directly related to the shell growth. The catalytic activity and stability of the Pd@Pt core–shell nanocubes in the methanol oxidation reaction were different for the nanocubes with partial and full Pt shells.