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.

Mn-based catalysts have exhibited promising performance in low-temperature selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). However, challenges such as H₂O- or SO₂-induced poisoning to these catalysts still remain. Herein, we report an efficient strategy to prepare the dual single-atom Ce-Ti/MnO₂ catalyst via ball-milling and calcination processes to address these issues. Ce-Ti/MnO₂ showed better catalytic performance with a higher NO conversion and enhanced H₂O- and SO₂-resistance at a low-temperature window (100−150 °C) than the MnO₂, single-atom Ce/MnO₂, and Ti/MnO₂ catalysts. The in situ infrared Fourier transform spectroscopy analysis confirmed there is no competitive adsorption between NO_x and H₂O over the Ce-Ti/MnO₂ catalyst. The calculation results showed that the synergistic interaction of the neighboring Ce-Ti dual atoms as sacrificial sites weakens the ability of the active Mn sites for binding SO₂ and H₂O but enhances their binding to NH₃. The insight obtained in this work deepens the understanding of catalysis for NH₃-SCR. The synthesis strategy developed in this work is easily scaled up to commercialization and applicable to preparing other MnO₂-based single-atom catalysts.