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.