Photothermal carbon dioxide (CO₂) methanation has attracted increasing interest in solar fuel synthesis, which employs the advantages of photocatalytic H₂O splitting as a hydrogen source and photothermal catalytic CO₂ reduction. This work prepared three-dimensional (3D) honeycomb N-doped carbon (NC) loaded with core–shell NiO@Ni nanoparticles generated in situ at 500 °C (NiO@Ni/NC-500). Under the photothermal catalysis (200 °C, 1.5 W/cm²), the CH₄ evolution rate of NiO@Ni/NC-500 reached 5.5 mmol/(g·h), which is much higher than that of the photocatalysis (0.8 mmol/(g·h)) and the thermal catalysis (3.7 mmol/(g·h)). It is found that the generated localized surface plasmon resonance enhances the injection of hot electrons from Ni to NiO, while thermal heating accelerates the thermal motion of radicals, thus generating a strong photo-thermal synergistic effect on the reaction. The CO₂ reduction to CH₄ follows the *OCH pathway. This work demonstrates the synergistic effect of NiO@Ni and NC can enhance the catalytic performance of photothermal CO₂ reduction reaction coupled with water splitting reaction.