Synergistic Effect of Nickel Nanoparticles Dispersed on MOF-Derived Defective CoO In Situ Grown over TiO Nanowires toward UV and Visible Light Driven Photothermal CO Methanation.

Catalytic CO hydrogenation is an effective approach to producing clean fuels, but this process is expensive, in addition to the low efficiency of catalysts. Thus, photothermal CO hydrogenation can effectively utilize solar energy for CH 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 CoO over 1D TiO nanowires (NWs). The original 3D dodecahedral structure of the MOF is engineered into novel 0D CoO nanospheres, which were uniformly embedded over Ni-dispersed 1D TiO NWs. In situ prepared 10Ni-7CoO@TiO NWs-I achieved an excellent photothermal CH 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 CH 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-7CoO/TiO NWs-M, the catalytic performance of the in situ approach is far superior, attributing to the morphological transformation of 0D CoO, 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 CO methanation.