Porous freestanding FeCoMnNiSe2 medium-entropy bifunctional electrocatalyst for oxygen and hydrogen evolution reactions in alkaline medium

Efficient bifunctional electrocatalysts towards oxygen and hydrogen evolution reactions (OER/HER) in water splitting is highly desirable for fuel cells and sustainable energy storage. Herein, one novel three-dimensional medium-entropy freestanding flower-like OER/HER bifunctional FeCoMnNi diselenide (FeCoMnNiSe2) electro-catalyst is fabricated by a facile hydrothermal and selenizing method. Benefiting from three-dimensional porous frame structure, lattice distortion and synergy effects, the as-prepared FeCoMnNiSe2 presents superior OER/HER bifunctional electrocatalytic activities with the quite low overpotentials of 223.1 mV for OER and 142.2 mV for HER at 100 mA cm-2 in 1.0 M KOH. More impressively, when employed for water splitting in a full cell, this bifunctional FeCoMnNiSe2 only requires ca. 1.42 V to drive the current densities of 100 mA cm-2 and displays outstanding stability for more than 60 h in 1.0 M KOH at 10, 50, 80 and 100 mA cm-2, surpassing almost all of reported advanced non-noble metal-containing OER/HER bifunctional electrocatalysts, and showing a promising potential application for industrial-scale water splitting.