High-Valence Nickel Single-Atom Catalysts Coordinated to Oxygen Sites for Extraordinarily Activating Oxygen Evolution Reaction.

Single-atom catalysts (SACs) are efficient for maximizing electrocatalytic activity, but have unsatisfactory activity for the oxygen evolution reaction (OER). Herein, the NaCl template synthesis of individual nickel (Ni) SACs is reported, bonded to oxygen sites on graphene-like carbon (denoted as Ni-O-G SACs) with superior activity and stability for OER. A variety of characterizations unveil that the Ni-O-G SACs present 3D porous framework constructed by ultrathin graphene sheets, single Ni atoms, coordinating nickel atoms to oxygen. Consequently, the catalysts are active and robust for OER with extremely low overpotential of 224 mV at current density of 10 mA cm, 42 mV dec Tafel slope, oxygen production turn over frequency of 1.44 S at 300 mV, and long-term durability without significant degradation for 50 h at exceptionally high current of 115 mA cm, outperforming the state-of-the-art OER SACs. A theoretical simulation further reveals that the bonding between single nickel and oxygen sites results in the extraordinary boosting of OER performance of Ni-O-G SACs. Therefore, this work opens numerous opportunities for creating unconventional SACs via metal-oxygen bonding.