Structural regulation and HER performance improvement of nanoporous FeCoNiPCB high-entropy alloys via a synergistic annealing–selective phase dissolution strategy

In this work, self-supported nanoporous FeCoNiPCB high-entropy alloys (HEAs) were fabricated through a synergistic annealing–selective phase dissolution strategy for efficient hydrogen evolution reaction (HER). By tuning the annealing temperature, the phase structure of the precursor was precisely regulated, which in turn governed the nanoporous architecture and the resulting HER electrocatalytic activity. Annealing at 716–798 K induces the transformation of the amorphous Fe₂₅Co₂₅Ni₂₅P₁₀C₁₀B₅ HEA ribbon into composite structures consisting of nano-sized α-(Fe, Co), (Ni, Co)₃P, and (Fe, Co)₃(C, B) phases embedded in a residual amorphous matrix. Subsequent electrochemical selective phase dissolution yields sandwich-like nanoporous FeCoNiPCB HEAs featuring a heterostructure mainly composed of (Ni, Co)₃P and (Fe, Co)₃(C, B) nanocrystals embedded in an amorphous matrix. Both the nanoporous morphology and phase constitution are dependent on the precursor phase structure. Notably, the nanoporous FeCoNiPCB HEA derived from the 757 K-annealed precursor exhibits the optimal HER performance, requiring overpotentials of 74.9 and 135.1 mV to deliver current densities of 10 and 100 mA cm⁻² in 1.0 M KOH solution, respectively. It also demonstrates superior stability over 50 h of continuous operation at 500 mA cm⁻². The enhanced HER activity is attributed to the synergistic interplay of the optimized nanoporous architecture and annealing-induced abundant nanocrystalline/amorphous heterointerfaces, which together provide a high density of accessible active sites and improved intrinsic catalytic activity. © 2026 Elsevier B.V.