Ni-O4 as Active Sites for Efficient Oxygen Evolution Reaction with Electronic Metal-Support Interactions.

Precise adjustment of the metal site structure in single-atom catalysts (SACs) plays a key role in addressing the oxygen evolution reaction (OER). Herein, we report the synthesis of O-doped Ni SACs anchored on porous graphene-like carbon (Ni-O-G) using molten salts (ZnCl2 and NaCl) as templates, in which the unique Ni-O4 structure serves as the active sites. Ni-O-G, with an overpotential of only 238 mV (@ 10 mA cm-2), is one of the more advanced catalysts. An array of characterizations and density functional theory calculations show that the Ni-O4 coordination enables Ni to be closer to the Fermi level compared to traditional Ni-N4, enhancing the electronic metal-support interaction to facilitate OER kinetics. Thus, this work offers an alternative strategy for the structural modulation of Ni SACs and the effect of different coordination elements with the same atomic coordination structure on the intrinsic OER activity.