<p>The synergy effect is effective strategy to enhance the transition-metal oxides electrocatalytic oxygen evolution reaction (OER) activities between the electrocatalyst and substrate. In this work, the precursor solutions of NiSO₄ • 6H₂O, Na₂S₂O₈, NH₄OH, and deionized water were used to directly prepare NiO nanosheets which grown on carbon nanotube (CNT)/carbon cloth (CC) substrates through a chemical bath method. Physical characterization revealed that the NiO nanosheets densely wrap around the CNTs, generating abundant the exposure of catalytically active edge sites, thereby significantly enhancing catalytic performance. The OER catalytic performance of NiO/CNT/CC and NiO/CC catalysts were studied and compared. The NiO/CNT/CC catalysts exhibits better OER catalytic performance with an overpotential of 418 mV at 100&#xa0;mA cm^− 2, a Tafel slope of 92.3 mV dec^− 1, an electrochemical surface area of 1035.0 cm² and charge transfer resistance of 0.21 Ω and great durability in alkaline solution. However, they are 518 mV, 166.7 mV dec^− 1, 202.5 cm² and 0.27 Ω for NiO/CC catalysts, respectively. Compared with NiO/CC catalysts, the excellent OER electrocatalytic activity of NiO/CNT/CC catalysts can be attributed to the synergy effect between NiO and CNT.</p> Graphical Abstract <p></p>