Ni-TiO2 catalysts derived from metal-organic framework for efficient photo-thermal CO2 methanation

Catalytic reduction of CO2 to high value-added chemicals such as methane is crucial in the development of renewable energy and waste disposal. Photo-thermal CO2 methanation has been received great attention, because the synergistic effect of photo and thermal lead to efficient CO2 reduction at low temperature. Herein, we reported the synthesis of Ni nanoparticles (NPs) supported on TiO2 (Ni-TiO2) derived from MIL-125 (Ti-MOFs) for photo-thermal CO2 methanation. The nanoparticle sizes and electron densities of metallic Ni, defects and chemical properties, photo-thermal and photo-electric characteristics of the catalysts have been systematically characterized by XRD, TEM, CO2/H2-TPD, XPS, photoluminescence and photocurrent. For the Ni-TiO2, the conversion of CO2 was 56 % under the full spectrum irradiation (1200 mW/cm2) at 325 °C, which was about 1.8 times of that without light irradiation. The selectivity of methane nearly 99 % with a production rate was 95.7 mmol/(gcat∙h), which was about 2.7 times of that without light irradiation. Meanwhile, the catalysts showed excellent stability without any activity decay during the four cycles testing (32 h). The main reasons for the high catalytic performance for photo-thermal CO2 methanation were attributed to the uniform distribution of Ni NPs with synergistic effect of large specific surface area of TiO2 with abundant moderate strength alkaline sites. In addition, good photo-thermal and photo-electric conversion ability make the catalysts possess more photo-generated charge carriers and reduce its recombination.