Microwave‐Driven Confinement Engineering of PtRuFeCoNi High‐Entropy Alloy Nanoparticles Within Hierarchically Porous Carbon Nanofibers for High‐Performance Trifunctional Electrocatalysis

Small‐sized high‐entropy alloy nanoparticles (HEA NPs) have recently emerged as promising candidates for applications in energy and catalysis, owing to their tunable composition, multi‐element synergistic effects, and exceptional structural stability. Nevertheless, achieving controlled synthesis of uniformly small HEA NPs remains challenging, as the high temperatures required for solid‐solution formation inevitably induce particle sintering. Herein, a spatial confinement strategy combined with rapid microwave heating is developed to synthesize ultrasmall PtRuFeCoNi HEA NPs (sub‐5 nm) embedded in hierarchically porous carbon nanofibers (PtRuFeCoNi‐PCNFs). The spatial confinement effect, attributed to the micro‐, meso‐, and macropores of the PCNFs, is crucial for the high dispersion of HEA NPs, while also enhancing the exposure of active sites and accelerating mass transport during electrochemical processes. PtRuFeCoNi‐PCNFs exhibit superior trifunctional electrocatalytic activity for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), with an ORR half‐wave potential of 0.837 V, and low overpotentials of 270 and 13 mV at 10 mA cm −2 for OER and HER, respectively. When applied in Zn‐air batteries and water splitting electrolyzers, PtRuFeCoNi‐PCNFs achieve high efficiency and outstanding durability. This study provides a novel perspective on designing and synthesizing high‐performance HEA NPs for energy and catalytic applications.