Hollow CoFeSe Nanocubes Supported on NiCoSe Nanosheet-DecoratedNi Foam as Electrocatalysts for Water Splitting

Transition metal selenides (TMSes) derived from Prussian blue analogues (PBAs) exhibit significant potential as electrocatalysts in water electrolysis. Nevertheless, their low active site utilization, insufficient catalytic activity, and poor stability severely constrain their practical application. In this study, two-dimensional (2D) NiCo-layered double hydroxide (LDH) grown on nickel foam (NF) was employed as the support, and three-dimensional (3D) hollow CoFe PBA was synthesized on its surface via a one-step method. After selenization, a bimetallic selenide (Co₂Fe)­Se₄/(CoNi)­(Se₂)₂/NF hollow nanocubes (CoFeSe/NiCoSe/NF-H) with a heterointerface and multilevel structure was successfully prepared. Due to the electron transfer mechanism at the heterointerface and the full exposure of active sites facilitated by the hierarchical structure, CoFeSe/NiCoSe/NF-H exhibits efficient bifunctional electrocatalytic activities for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with overpotentials of 82 mV (η₁₀) and 288 mV (η₁₀₀) in 1 M KOH, respectively. Additionally, it achieves a current density of 10 mA cm^–2 at 1.52 V during the overall water splitting. The study presents a valuable approach to enhancing the performance of PBA-derived nanoscale electrocatalytic materials through heterostructure formation and morphology engineering.