In-situ electrostatic anchoring of highly oxidized Ir single atoms on NiFe LDH for efficient water oxidation

Single atom catalysts could tune the catalytic center local coordination environment and enhance metal-carrier interactions, allowing for activating the oxygen evolution reaction (OER) activity of the relatively inert NiFe layered double hydroxide (LDH) basal plane. However, the control of the monoatomic active sites and in-depth understanding of the mechanism are still significant challenges. Here, an in-situ electrostatic adsorption anchoring strategy is introduced to deposit Ir single atoms (SAs) onto NiFe LDH (Ir/NiFe LDH) nanosheets by a facile one-step electroreduction procedure. When the electronic structure of the NiFe LDH basal plane is optimized, the nuanced structure characterizations reveal that Ir SAs interact with NiFe LDH in Ir-O bonds and exhibit a highly oxidized state (+5.5). Electrochemical tests coupled with Raman spectroscopy and theoretical calculations show that Ir SAs could promote the conversion of NiFe LDH to the active phase Ni2+delta-O-Fe3+zeta OxHy and lower the reaction energy barrier with accelerating OER. As a result, Ir/NiFe LDH delivers a low overpotential of 202 mV at 10 mA cm-2 and maintains excellent OER durability after 200 h of operation at the high current density of 100 mA cm-2, surpassing the NiFe LDH and commercial IrO2 catalysts. This work offers an excellent avenue to synthesize single atom catalysts and illustrate single atom catalytic mechanisms in OER in this system, opening a new path to apply SAs/LDH type catalysts for water splitting.