Rational construction of uniform CoS/NiFe2O4 heterostructure as efficient bifunctional electrocatalysts for hydrogen evolution and oxygen evolution reactions

The development of efficient bifunctional electrocatalyst for hydrogen evolution reaction (HER) and oxy-gen evolution reaction (OER) in alkaline environment is crucial and challenging for large-scale hydrogen energy application. Herein, a heterostructure electrocatalyst on Ni foam (NF) with CoS nanosheet coupled with NiFe2O4 was synthesized via electrodeposition method with the assistant of thiourea followed by annealing treatment. Because of the unique three-dimension structure, this self-supported catalyst pos-sesses high intrinsic conductivity, abundant active sites and excellent durability, acting as an exceptionally durable and efficient catalyst for HER and OER. The obtained CoS/NiFe2O4-15/NF exhibits HER and OER catalytic performance with overpotentials of 116 mV and 227 mV at a current density of 10 mA cm -2 in 1 M KOH, respectively. For CoS/NiFe2O4-15/NF||CoS/NiFe2O4-15/NF two-electrode system, the electrolyser requires 1.60 V to deliver 10 mA cm -2, and negligible loss of activity is observed after working for 12 h (10 mA cm -2). Moreover, the interface between oxide and sulfide is identified to play a major part in the catalysis of OER and HER. These excellent properties of CoS/NiFe2O4-15/NF electrode advance the electronic water splitting reaction for hydrogen production. (c) 2021 Elsevier Ltd. All rights reserved.