Laser‐Induced Solid‐State Synthesis of Multimetallic Phosphide Nanoparticles in Ambient Air

Multimetallic phosphide nanoparticles (MMP NPs) represent an emerging class of functional nanomaterials with exceptional tunability and synergistic electronic properties; however, their scalable synthesis under ambient conditions remains a major challenge. Herein, we report a universal laser‐assisted strategy for the direct synthesis of MMP NPs on carbon paper in air via a rapid two‐step process involving laser‐induced alloying and subsequent solid‐state phosphidation. Enabled by a continuous‐wave blue diode laser, this approach generates a highly localized, ultrahigh‐temperature nonequilibrium environment that facilitates carbothermal reduction, multimetallic alloy formation, and subsequent phosphidation without inert atmospheres or post‐annealing. The method is composition‐agnostic and readily extendable to a CO 2 laser platform, allowing the synthesis of a series of MMP NPs ranging from binary to septenary compositions with homogeneous elemental distributions, even among normally immiscible metals. As a representative example, FeNiCoP exhibits outstanding oxygen evolution reaction activity in alkaline seawater, delivering an overpotential of 0.301 V at 100 mA cm −2 , along with excellent long‐term durability over 680 h of continuous operation. This work establishes a scalable, versatile laser‐based platform for the ambient synthesis of complex multimetallic phosphides and broadens the toolbox for advanced functional nanomaterials synthesis.