Active bimetallic Fe–O–Co sites built on 2D trimetallic complex spinel oxides for industrially oxygen evolution electrocatalyst

Fabrication of active and durable non-noble metal heterogeneous electrocatalysts to settle the relatively slow kinetic process and poor stability during the oxygen evolution reaction (OER) process is of great significance. Herein, we fabricate in-situ 2D Fe-based trimetallic complex spinel oxide nanosheets (FeCoNi)O 4 via a polyethylene glycol-barbituric acid deep eutectic solvent-assisted route. Multiple analytical characterizations illustrate a deep understanding of the structure and composition of (FeCoNi)O 4 , disclosing Fe, Co, and Ni ions occupy both tetrahedrally and octahedrally coordinated positions. Meanwhile, the synergistic actions of preparing multiple-cations substitution and constructing oxygen vacancy activate covalent Fe–O–Co bonds in (FeCoNi)O 4 . Due to the active bimetallic Fe–O–Co sites, enhanced electronic conductivity and unique structure stability, the synthesized 2D (FeCoNi)O 4 nanosheets exhibit excellent OER performance with relatively low overpotential (421 mV for 1000 mA/cm 2 ) and long-term stability (720 mA/cm 2 for 6 h) in alkaline media, which is much better than that of Fe-based bi/monometallic spinel oxides. In-situ Raman spectra and quasi-in-situ X-ray photoelectron spectroscopy results depict that O-bridged Fe–O–Co bimetallic sites promote the formation of μ(O–O) intermediates and undergo the direct O 2 evolution route, thus accelerating OER.