Synergistic Effect of Nickel Nanoparticles Dispersed on MOF-Derived Defective Co₃O₄ In Situ Grown over TiO₂ Nanowires toward UV and Visible Light Driven Photothermal CO₂ Methanation

Catalytic CO₂ hydrogenation is an effective approach to producing clean fuels, but this process is expensive, in addition to the low efficiency of catalysts. Thus, photothermal CO₂ hydrogenation can effectively utilize solar energy for CH₄ production. Metal-organic framework (MOF) derived materials with a controlled structure and morphology are promising to give a high number of active sites and photostability in thermal catalytic reactions. For the first time, a novel heterostructure catalyst was synthesized using a facile approach to in situ grow MOF-derived 0D Co₃O₄ over 1D TiO₂ nanowires (NWs). The original 3D dodecahedral structure of the MOF is engineered into novel 0D Co₃O₄ nanospheres, which were uniformly embedded over Ni-dispersed 1D TiO₂ NWs. In situ prepared 10Ni-7Co₃O₄@TiO₂ NWs-I achieved an excellent photothermal CH₄ evolution rate of 8.28 mmol/h at 250 °C under low-intensity visible light, whereas UV light treatment further increased activity by 1.2-fold. UV irradiations promoted high CH₄ production while improving the susceptibility of the catalyst to visible light irradiation. The photothermal effect is prominent at lower temperatures, due to the harmonization of both solar and thermal energy. By paralleling with mechanically assembled 10Ni-7Co₃O₄/TiO₂ NWs-M, the catalytic performance of the in situ approach is far superior, attributing to the morphological transformation of 0D Co₃O₄, which induced intimate interfacial interactions, formation of oxygen vacancies and boosted photo-to-thermal effects. The co-existence of metallic/metal oxide Ni-Co provided beneficial synergies, enhanced photo-to-thermal effects, and improved charge transfer kinetics of the composite. This work uncovers a facile approach to engineering the morphology of MOF derivatives for efficient photothermal CO₂ methanation.