Through long-term support provided by the Ministry of Science and Technology and the National Synchrotron Radiation Research Center (NSRRC), a multinational research team including National Taiwan University utilized their exclusive “operando X-ray absorption spectroscopy” to discover a new catalyst – single-atom iron with a high valence of +3 – that can perform a superior activity and potentially substitute for gold, silver, or other precious metals. Such a highly active catalyst can electrochemically convert CO2 into CO with a high conversion efficiency and a low energy consumption, greatly reducing the cost of catalysts. This recycle of CO2 in a highly efficient manner can not only slow the global warming but also produce CO that can be further converted into other valuable fuesls for relative chemical industry. The exceptional results of their study have been published on June 14 of this year (2019) in global top journal《Science》.
The research team formed by Prof. Hao-Ming Chen from the Department of Chemistry at NTU and Prof. Xile Hu from Swiss Federal Institute of Technology Lausanne and their group members has spent three years through using both “Taiwan Light Source” and “Taiwan contracted beamline at Japan’s synchrotron radiation facility (SPring-8)” of the NSRRC in utilizing “Operando X-ray absorption spectroscopy” technology for real-time observation of the catalytic valence and chemical environment during the electrochemically CO2 reduction into CO. The result successfully reveals a new low cost catalyst and mades a breakthrough that has attracted global attention.
Because CO2 has a significant impact on climate change, the electrochemical CO2 reduction reaction has been regarded as a promising way to convert carbon dioxide into chemical fuels, which can potentially provide a perfect carbon cycle with carbon capture techniques and renewable energy if the electricity was generated through a clean approach. Prof. Hao-Ming Chen points out that some precious metals such as gold or silver are characteristic of excellent activity toward the CO2 reduction into CO, while other non-precious catalysts require extremely high voltage to achieve a similar performance. However, high voltage input as well as large energy consumption are unable to meet the requirements of economic benefit. This study is the first demonstration that single-atom dispersed iron ions in a +3 oxidation state can reduce CO2 to CO at a faradaic efficiency of 90% even with extremely low voltage. This is the state-of-the-art catalyst with the best conversion efficiency and even superior to those of the precious metals. In this study, a critical problem why this catalyst can perform the best activity among all the state-of-the-art catalysts is raised. In order to realize the key mystery of such high conversion efficiency, Prof. Chen utilized the beamlines of NSRRC in Taiwan and Japan in combination with the operando X-ray absorption spectroscopy technology developed by Prof. Chen’s group in recent years. They evidently clarified that the key is to stabilize the active site in +3 state during the CO2 reduction.
It’s worth mentioning that the new single-atom iron catalyst can recycle CO2 in a high-efficient and cost-effective manner with producing CO. The produced CO can be further converted into hydrocarbons to create fuels, plastics, and other materials. This kills two birds with one stone as it can reduce the amount of substances causing global warming and can produce fuels. Prof. Chen states that future diections will attempt to use solar energy as a replacement for generating electricity toward the CO2 reduction reaction. This will achieve the goal of “artificial photosynthesis”, a massive milestone in modern technology.
Many exceptional research results have been produced over the past 20 years from both Taiwan’s and Japan’s synchrotron radiation beamlines of NSRRC. “Taiwan Photon Source” activated in 2016 is currently one of the brightest light sources in the world, where many beamlines are constructed for the research in the relative fields of green energy and biomedicine. In the future, this will assist the top domestic and foreign scientists in producing countless breakthroughs in research. NSRRC stated that in recent years, operando X-ray absorption spectroscopy technology has been broadly applied in the fields of catalysis and electrochemistry to clearly understand the electronic and atomic structures of the catalytic manners during the chemical reactions. Prof. Chen used this key technique to successfully reveal the key of maintaining the single-atom iron in a high oxidation state. This is a new discovery on a global scale.
The “Paris Climate Agreement” in 2015 was a call to action for every country to achieve the zero-carbon emissions by 2050. In June of this year (2019), the UK signed “net-zero carbon emissions by 2050” into law and Taiwan’s government is also advocating for a green energy policy. Prof. Hao-Ming Chen states that this study complies with international trends of green energy and has great commercial value in future development.
Professor Hao-Ming Chen
Department of Chemistry, National Taiwan University
Dr. Ting-Yang Kuo
Department of Natural Sciences and Sustainable Development,
Ministry of Science and Technology