The development of efficient and cost-effective oxygen evolution reaction(OER)electrocatalysts is cru-cial for clean energy conversion and storage devices,such as water-splitting,CO2 reduction,and metal-air batteries.Herein,we report an efficient 2-dimensional OER catalyst of ultrathin nickel-iron sulfide nanosheets(NiFeS-NS).Dodecanethiol is employed in the synthesis,which prohibits the growth along the Z-axis,thus a nanosheet is obtained.The NiFeS-NS shows high OER catalytic activity,which only requires a small overpotential of 273 mV to achieve the OER current density of 10 mA/cm2 in alkaline electrolyte,and almost no decay after 150 h of chronopotentiometry test.The high performance is attributed to the 2-dimensional structure,the synergistic effect from the Ni and Fe components which promotes the for-mation of the high valence Ni species,and the tuning effect from the in-situ generated sulfate doping.This work demonstrates the advantages of the 2-dimensional sulfides in electrocatalysis.