• Electrochemical activation of V-doped NiFe-LDH nanosheets on carbon cloth induces surface reconstruction to form NiOOH, which serves as the active phase for OER.
• The release of doped V during activation creates abundant vanadium and oxygen vacancies, enhancing intrinsic activity and electrical conductivity.
• The NiOOH/NiFeV-LDH@CC catalyst exhibits low overpotentials of 209 mV and 241 mV at 20 and 100 mA cm−2, respectively, and long-term stability over 80,000 s.
• An overall water splitting cell using this catalyst as anode achieves 20 mA cm−2 at 1.597 V without iR compensation, demonstrating practical applicability.