43 Modifcation of SiO 2 -Al 2 O 3 Supported TiO 2 for Photocatalytic Reduction of CO 2 to Methanol Nakarin DUANGKAEW ※1※2※3 , Nanthachat SUPAREE ※1※2※3 , Pakpoom ATHIKAPHAN ※1※2※3 , Arthit NERAMITTAGAPONG ※1※2※3 , Somnuk THEERAKULPISUT ※4 , Rattabal KHUNPHONOI ※5 , Narong CHANLEK ※6 , and Sutasinee NERAMITTAGAPONG ※1※2※3† (Received January 5, 2021) The photocatalytic reduction of carbon dioxide into methanol over modifed SiO2-Al2O3 supported TiO2 catalyst at atmospheric pressure was investigated. The SiO 2-Al2O3 supported TiO2 catalyst was modifed by coating the bimetallic metal (Ni-Cu) using the sol-gel method with various Ni-Cu loading in the range of 0wt.% to 5wt.%. All prepared catalysts were characterized using Scanning electron microscopy (SEM), X-ray powder difraction (XRD), N 2 adsorption-desorption, UV-vis diffuse reflectance spectrometer (UV-Vis-DRS), and Photoluminescence Spectroscopy (PL). The reaction was performed in a liquid-phase batch-reactor equipped with a UVC lamp (125W) as a source of UV radiation. The reactions were tested at atmospheric pressure and the temperature of 25 °C for 5 h with a catalyst loading of 4 g/L. It was found that the coating of bimetallic metal had efects on the reduction of surface area and energy bandgap. The prepared catalyst had a surface area in the range 108 m 2 /g to 199.6 m 2 /g, and the bandgap energy varied from 3.01 eV to 3.08 eV. The presence of Ni (3wt.%) and Cu (2wt.%) on the TiO2/ SiO 2-Al2O3 catalyst had slower recombination rate of electron-hole pairs than that of TiO2/SiO2-Al2O3 catalyst. The highest methanol production rate of 405.08 µmol/g cat was obtained after 2 h over 3wt.%Ni-2wt.%Cu-TiO2/SiO2-Al2O3. This production rate was three times higher than that over unmodifed TiO 2/SiO2-Al2O3 due to good retardation of electron-hole pair recombination. Key Words Renewable energy, Methanol production, Carbon dioxide capture, Photosynthesis ※1 Department of Chemical Engineering, Faculty of Engineering, Khon Kaen University Khon Kaen 40002, Thailand ※2 Research Center for Environmental and Hazardous Substance Management (EHSM), Khon Kaen University Khon Kaen 40002, Thailand ※3 Center of Excellence on Hazardous Substance Management (HSM) Pathumwan, Bangkok 10330, Thailand Journal of the Japan Institute of Energy , 101 , 43-49（2022） Original Paper ※4 Energy Management and Conservation Ofce, Faculty of Engineering, Khon Kaen University Khon Kaen 40002, Thailand ※5 Department of Environmental Engineering, Faculty of Engineering, Khon Kaen University Khon Kaen 40002, Thailand ※6 Synchrotron Light Research Institute (Public Organization) Nakhon Ratchasima 30000, Thailand †Corresponding author: sutasineene@kku.ac.th The content of this paper was presented at JCREN2020. 1.　Introduction The ever-increasing CO2 concentration is the most important contributor to the greenhouse gases in the Earth's atmosphere. The increasing CO2 is mainly due to the combustion or burning of fossil fuels and wastes which affect the environment and health. Therefore, solving the problem of CO2 has been a major and open research issue. One possible solution is to synthesize CO2 to produce fuels which can be achieved by various methods, such as hydrogenation method 1) and electrochemical method 2) . Moreover, these methods are not favorable because they are costly and energy-intensive. In recent decades, photocatalytic reduction of CO2 into hydrocarbon compounds has become popular due to its environmentally friendly nature 3) . However, this process requires some semiconductors as catalysts. Usually, the most important