Core-shell structured Co(OH)F@FeOOH enables highly efficient overall water splitting in alkaline electrolyte

Constructing a low-cost, high activity and stable electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) via overall water splitting is of great significance, but remains a big challenge. In this work, vertically aligned core-shell Co(OH)F@FeOOH nanorod arrays (NRs) on Ni foam were constructed via hydrothermal and chemical deposition methods. Due to the synergistic effects and electron interaction at the interface between Co(OH)F and FeOOH, the synthesized core-shell Co(OH)F@FeOOH heterostructure exhibits remarkable OER and HER catalytic activity in 1 M KOH solution, presenting low overpotentials of approximately 205 mV and 137 mV at a current density of 10 mA cm−2, and low Tafel slopes of approximately 48 mV dec−1 and 86 mV dec−1, for OER and HER, respectively. Moreover, the synthesized Co(OH)F@FeOOH serves as a bifunctional electrocatalyst for overall water splitting and it only needs 1.55 V to drive the electrolysis cell yielding 10 mA cm−2 which is much lower than that of 1.68 V for IrO2||Pt/C and showing excellent stability for 37 h. The prepared Co(OH)F@FeOOH catalyst has been successfully used in solar cell-driven water electrolysis, demonstrating its great potential for cost-effective electrochemical hydrogen production.