Hierarchical Co-FeS₂/CoS₂ heterostructures as a superior bifunctional electrocatalyst

The traditional method of preparing hydrogen and oxygen as efficient clean energy sources mainly relies on the use of platinum, palladium, and other precious metals. However, the high cost and low abundance limit wide application of such metals. As such, one challenging issue is the development of low-cost and high-efficiency electrocatalysts for such purposes. In this study, we synthesized Co-FeS₂/CoS₂ heterostructures via a hydrothermal method for efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Benefitting from their unique three-dimensional hierarchical nanostructures, Co-doped FeS₂, and CoS₂ formed heterostructures on Co-FeS₂ petals, which bestowed remarkable electrocatalytic properties upon Co-FeS₂/CoS₂ nanostructures. Co-FeS₂/CoS₂ effectively catalyzed the OER with an overpotential of 278 mV at a current density of 10 mA cm^-2 in 1 M KOH solution, and also is capable of driving a current density -10 mA cm^-2 at an overpotential of -103 mV in 0.5 M H₂SO₄ solution. The overpotential of the OER and HER only decreased by 5 mV and 3 mV after 1000 cycles. Our Co-FeS₂/CoS₂ materials may offer a promising alternative to noble metal-based electrocatalysts for water splitting.