The rational design of Ni-based catalysts is essential due to their abundance and low cost for advancing sustainable energy technologies, particularly for water splitting and fuel cells. This study employs spin-polarized density functional theory (DFT) to examine the influence of anchoring rare-earth elements on the γ-NiOOH lattice surface, aiming to identify the optimal catalytic site for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Following the identification of an appropriate active site through Ni vacancy, a rare earth element (REE1) is introduced as a dopant for single-atom catalysis (SACs). The structural, thermodynamic, and catalytic characteristics of all newly designed REE1/γ-NiOOH catalysts have been extensively studied. Among the newly developed catalysts, Tb1/γ-NiOOH exhibits the lowest OER overpotential of (0.36 V), while Ce1/γ-NiOOH and Pr1/γ-NiOOH also demonstrate excellent OER performance (0.51 and 0.41 V), respectively. Notably, Nd1/γ-NiOOH and Pm1/γ-NiOOH exhibit efficient ORR activity, with low overpotentials of (0.63 and 0.61 V) due to their balanced adsorption and desorption energies of intermediates. Bader charge analysis reveals strong electron donation from doped REE1 to the surface. This study identified Ce1, Pr1, Nd1, and Tb1 anchoring catalysts as highly promising for water-splitting applications. Moreover, Nd1 and Pm1 doping markedly improve ORR performance, underscoring their promise for enhanced electrochemical applications in metal-air batteries. The catalytic performance of all newly developed catalysts was further evaluated using electronic descriptors. The catalytic performance was further assessed using the volcano curve and scaling relationships for the adsorbed intermediates. This study offers an extensive theoretical foundation for designing cost-effective and high-performance REE1/γ-NiOOH electrocatalysts. © 2025 Elsevier B.V., All rights reserved.