Morphology Control of Platinum Particles Grown on a Liquid Metal Interface

Galvanic replacement reaction (GRR) is a versatile electrochemical strategy for constructing complex heterostructures. However, achieving controlled synthesis of noble-metal nanoparticles with defined morphologies and spatial distributions on an unconventional gallium-based liquid-metal (LM) surface remains highly challenging and largely unexplored. In this work, we systematically investigated the GRR between LM droplets and Pt precursors with different chloride coordination: K₂PtCl₄ ([PtCl₄]^2-, tetra-coordinated) and K₂PtCl₆/(NH₄)₂PtCl₆ ([PtCl₆]^2-, hexa-coordinated). By deliberately exploiting the differences in thermodynamic driving forces and kinetic pathways associated with these ligand configurations, we demonstrate that the coordination environment of Pt complexes serves as an effective handle to regulate Pt nucleation and growth. Consequently, the [PtCl₄]^2- complex yields uniformly distributed, satellite-like Pt domains, whereas the [PtCl₆]^2- complex produces sparsely localized, patch-like Pt deposits. These distinct morphologies and deposition modes of Pt particles modulate interfacial stress, driving LM droplet evolution and divergent macroscopic transformations. In particular, the oxide layer formed on LM surfaces, together with Pt-catalyzed hydrogen evolution, was confirmed as a primary factor governing LM transformations across multiscale. Overall, this study deepens the fundamental understanding of LM-based GRR mechanisms and demonstrates a coordination-tuning strategy for designing noble-metal-coated LM heterostructures with tailored morphologies and spatial distributions, which could enable their use as reconfigurable functional materials in a broad range of applications.