Engineering bimetallic cactus-like NiFeOOH/CoNiSe2 heterostructure nanosheets for efficient oxygen evolution and overall water splitting

The development of structural stable, high-performance, inexpensive electrocatalysts for oxygen evolution reactions (OER) is essential to alleviate the energy crisis. Herein, cactus-like CoNiSe2 was synthesized on nickel foam and NiFeOOH was electrodeposited on surface of CoNiSe2 to form a core-shell structural electrode. The obtained NiFeOOH/CoNiSe2/NF exhibited ultra-low overpotentials of 204 mV and 234 mV at 10 and 100 mA cm−2, with a Tafel slope of 26.2 mV dec−1 in 1 M KOH alkaline solution. Furthermore, the current density only decreased by 5% after a 100 h durability test at 200 mA cm−2, showing excellent robust stability. A two-electrode system with NiFeOOH/CoNiSe2/NF as anode and Ni/NiO@MoO3-x/NF as cathode (NiFeOOH/CoNiSe2/NF||Ni/NiO@MoO3-x/NF) showed a low voltage of 1.47/1.56 V to deliver 10/100 mA cm−2. According to the experimental and density functional theory (DFT) results, the strong electronic interactions at the NiFeOOH/CoNiSe2/NF interface leads to an increase in the valence state of Fe and an optimisation of the adsorption free energy, which are favourable to reduce the energy consumption of the OER. This work obtained high performance OER electrocatalysts by engineering amorphous and crystalline heterointerfaces and structural design, which will provide some inspiration for similar work.