Oxygen evolution reaction (OER) has attracted enormous interest as a key process for water electrolysis over the past years. The advance of this process relies on an effective catalyst. Herein, we employed single-atom Au doped Co-based nanosheets (NSs) to theoretically and experimentally evaluate the OER activity and also the interaction between Co and Au. We reveal that Au–Co(OH)₂ NSs achieved a low overpotential of 0.26 V at 10 mA cm⁻². This extraordinary phenomenon presents an overall superior performance greater than state-of-the-art Co-based catalysts in a sequence of α-Co(OH)₂ < Co₃O₄ < CoOOH < Au–Co(OH)₂. With ab initio calculations and analysis in the specific Au–Co(OH)₂ configuration, we reveal that OER on highly active Au–Co(OH)₂ originates from lattice oxygen, which is different from the conventional adsorbate evolution scheme. Explicitly, the configuration of Au–Co(OH)₂ gives rise to oxygen non-bonding (O_NB) states and oxygen holes, allowing direct O–O bond formation by a couple of oxidized oxygen with oxygen holes, offering a high OER activity. This study provides new insights for elucidating the origins of activity and synthesizing efficient OER electrocatalysts.