Unlocking Vacancy‐Mediated Cation Exchange in Transition Metal Phosphides: Toward Architected Catalytic Nanostructures

Cation exchange (CE) has emerged as a powerful strategy for postsynthetic modification of nanomaterials, enabling access to metastable phases, complex morphologies, and novel functionalities. While extensively studied in chalcogenide systems, CE in transition metal phosphides (TMPs) remains underexplored despite their significance in catalysis and energy applications. Herein, a comprehensive study of CE in TMPs using Cu 3− x P as a structurally versatile and vacancy‐rich platform is reported. The exchange of copper with nickel is systematically investigated and the approach to other transition metal cations including Co 2+ , Pd 2 + , Mo 3 + , and Ga 3 + is extended. Compared to their directly synthesized counterparts, the structures obtained via CE demonstrate superior preservation of particle size and morphology, more sharply defined interfacial domains, and a distinctive reconfiguration of the anionic phosphorus framework. Structural evolution is monitored using X‐ray diffraction, electron microscopy, energy dispersive spectroscopy, and X‐ray photoelectron spectroscopy, unveiling a rapid CE process with over 90% completion within 90 s. The role of the anionic sublattice highlights a vacancy‐mediated restructuring mechanism, offering a route to design TMP nanostructures with tailored architectures. This study establishes CE as a versatile and efficient method for engineering functional TMPs, potentially advancing the design of next‐generation electrocatalysts for renewable energy technologies.