Mesoporous-nanoreactor-confined PtRuNiCoCu high-entropy alloy nanoparticles for superior alkaline hydrogen oxidation reaction

Sub-3 nm PtRuNiCoCu HEA NPs were synthesized via a nanoreactor-confined strategy. • Mesoporous NHCS confinement ensures a uniform single-phase FCC HEA structure. • The spatially separated dual sites for H* and OH* optimize HOR kinetics. • The catalyst shows high alkaline HOR mass activity (3329.32 A g −1 ) and CO tolerance. To address the sluggish hydrogen oxidation reaction (HOR) kinetics in anion exchange membrane fuel cells (AEMFCs), a PtRuNiCoCu@NHCSs electrocatalyst is developed through the in situ synthesis of ultrasmall (<3 nm) PtRuNiCoCu high-entropy alloy nanoparticles (HEA NPs) confined within hollow mesoporous nitrogen-doped carbon spheres (NHCSs), using a vapor-infusion-assisted pyrolytic reduction strategy. The nanoreactor confinement provided by NHCSs suppresses phase separation, yielding a single-phase face-centered cubic structure, ensures uniform dispersion and stability of the HEA NPs. The ultrasmall nanoparticle size provides a large electrochemically active surface area and abundant accessible active sites. Electronic interactions among the multimetallic components create electron-rich and electron-deficient regions on the HEA surface, forming spatially separated dual-active sites for H* and OH*, which mitigates competitive adsorption and generates a broad distribution of adsorption energies. This establishes multiple low-energy reaction pathways, collectively lowering the HOR barrier, while simultaneously weakening CO binding. These synergistic structural and electronic effects endow the PtRuNiCoCu@NHCSs catalyst with outstanding alkaline HOR performance, achieving a mass activity of 3329.32 A g −1 Pt+Ru and an exchange current density of 9.43 mA cm −2 , along with remarkable durability and CO tolerance. This study provides both a general synthesis route for ultrasmall HEAs and a mechanistic framework for designing advanced AEMFC electrocatalysts. Download: Download high-res image (160KB) Download: Download full-size image