Synergistically integrated CoS@NiFe-layered double hydroxide core-branch hierarchical architectures as efficient bifunctional electrocatalyst for water splitting.

Efficient, low-cost, and robust electrocatalysts development for overall water splitting is highly desirable for renewable energy production yet still remains challenging. In this work, CoS nanoneedles arrays are synergistically integrated with NiFe-layered double hydroxide (NiFe-LDH) nanosheets to form CoS@NiFe-LDH core-branch hierarchical architectures supported on nickel foam (CoS@NiFe-LDH HAs/NF). The CoS@NiFe-LDH HAs/NF exhibits high catalytic performances for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with overpotential of 190 and 145 mV at 10 mA cm, respectively. The density functional theory calculations predict that the synergy between CoS and NiFe-LDH contributes to the high catalytic performance by lowering the energy barrier of HER. When used as both anode and cathode electrocatalyst, it can deliver 10 mA cm at a low cell voltage of 1.585 V with excellent long-term durability. This work opens a new avenue toward the exploration of highly efficient and stable electrocatalyst for overall water splitting.