DGIST-Caltech joint research team develops ‘artificial photosynthesis catalyst’ that converts carbon dioxide into fuel using sunlight

□ A research team led by Professor Suil In of the Department of Energy Science and Engineering at DGIST (President Kunwoo Lee) in cooperation with a research team led by Professor William A. Goddard III of the California Institute of Technology (Caltech) developed a highly efficient photocatalyst that can convert carbon dioxide into the high-value-added fuel, methane, using sunlight, while explaining its operating principles.

□ Carbon dioxide is a typical greenhouse gas, considered a major cause of climate change, and developing technologies to effectively reduce it is an important challenge worldwide. The ‘photocatalyst’ technology that caught the interest of the research team is a type of ‘artificial photosynthesis’ technology that uses solar energy to convert carbon dioxide into fuel. It has garnered significant attention for its potential to contribute to carbon neutrality and eco-friendly energy production.

□ The research team combined ‘silver sulfide (Ag₂S),’ which absorbs visible and near-infrared light well, with titanium dioxide (TiO₂), a widely used photocatalytic material, and developed a new structure that allows electrons to efficiently move through Z-scheme, a channel similar to natural photosynthesis in the natural world. This significantly improved the efficiency of light energy usage.

□ Previous studies had limitations as the materials remained in the regular crystalline state for too long and lacked ‘active sites’ where carbon dioxide can actually react. The DGIST-Caltech joint research team intentionally introduced ‘defects’ into the material to create plenty of titanium tertiary (Ti³⁺) active sites using amorphous titanium dioxide with an irregular structure and combined non-stoichiometric silver sulfide nanowires, designed to have an atomic ratio that does not perfectly match in order to form a strong electric field inside. By doing so, they successfully improved charge separation and reaction efficiency dramatically.

□ As a result, the newly developed photocatalyst achieved a methane production rate of 30.31 μmol/g in a concentrating reactor environment, an approximately fivefold improvement in performance compared to ordinary conditions. This research holds great significance for it scientifically demonstrates that ‘defects’ are not simply structural limitations but can actually be a key factor in improving catalyst performance.

□ Professor Suil In stated, "This research is significant as it suggests the possibility of designing and controlling the 'active sites' that determine catalyst efficiency. This will contribute to quickening the commercialization of the technology that converts carbon dioxide into valuable fuel." He added, “The fact that this research elucidated the process of carbon dioxide conversion into methane at the atomic level by combining experimental research and quantum mechanical calculations is also a significant achievement."

□ This research was funded by the National Research Foundation of Korea's Individual Basic Research Program (Mid-Career Research), and the results were published in the prestigious international journal ‘ACS Catalysis,’ published by the American Chemical Society (ACS).