The efficiency of converting carbon dioxide into formic acid using recycled used batteries exceeds 93%

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Recently, through a collaboration between Professor Yao Tao’s team from the **Synchrotron Radiation Laboratory** at the University of Science and Technology of China and Professor Xia Baoyu’s team at Huazhong University of Science and Technology, among others, various synchrotron radiation in-situ techniques were employed to make significant progress in the study of the mechanism by which carbon dioxide is converted using proton exchange membranes. An electrolysis system was also developed that enables the conversion of carbon dioxide from used batteries into formic acid, which holds high economic value; this approach is of great significance for addressing energy and environmental issues. The relevant research findings were published in the journal Nature. 　　Developing various carbon-neutral technologies is of great significance for addressing energy and environmental issues. Electrocatalytic carbon dioxide conversion based on proton exchange membrane technology can produce high-value chemicals and fuels, and it is capable of operating stably at high currents for extended periods of time; it is thus one of the more promising approaches for industrial-scale carbon conversion. Using the various advanced characterization techniques available at synchrotron radiation large-scale scientific facilities to study the structural evolution and reaction mechanisms of catalysts under operational conditions holds great scientific significance and practical value for the development of acid-stable carbon conversion catalysts and membrane electrode systems. 　　Based on this, the researchers prepared recycled lead catalysts using used lead-acid batteries, and utilized these recycled lead catalysts to achieve high electrocatalytic activity for carbon dioxide conversion over a wide pH range. At a voltage of 2.2 volts and under continuous operation for 5200 hours, this method achieves a Faradaic efficiency of over 93% for the production of formic acid, with a current density of 600 milliamps per square centimeter. 　　It is understood that in order to determine the true active structure of lead recycling catalysts in the electrocatalytic conversion of carbon dioxide, researchers developed and designed an in-situ device for membrane electrode electrocatalytic carbon dioxide conversion suitable for X-ray absorption spectroscopy, and carried out offline as well as in-situ characterizations at the soft X-ray magnetic circular dichroism station of the Hefei Light Source and the XAFS station of the Beijing Light Source. Using in-situ X-ray absorption spectroscopy, the researchers discovered that the regenerated lead catalyst underwent dynamic structural changes at the reduction potential for the electrocatalytic conversion of carbon dioxide. The coexistence of metallic lead and lead carbonate in a certain proportion at this reduction potential was the key factor behind the high selectivity and activity in the production of formic acid. 　　Furthermore, relying on the in-situ infrared spectroscopy techniques of the Hefei Light Source as well as a self-developed in-situ infrared apparatus, the researchers conducted in-situ infrared studies on the electrocatalytic conversion of carbon dioxide using carbon-13 isotopically labeled carbon dioxide. They found that gaseous carbon dioxide on the surface of lead carbonate first undergoes a surface activation process before entering the lead carbonate lattice, where the carbon within the lattice is then converted into the final formate product. By combining theoretical calculations, the researchers revealed the mechanism by which solid-state dynamic transitions in recycled lead catalysts induce lattice carbon activation and carbon dioxide conversion. 　　Yao Tao said that this research finding enables the conversion of carbon dioxide into formic acid, which has high economic value, using recycled used batteries, and thus holds significant practical value for achieving carbon neutrality. Xia Baoyu believes that as it develops further, this technology can be used in carbon-intensive industries such as fossil fuel companies to help them reduce their carbon footprint. Next, the research team hopes to convert carbon dioxide into products that are more valuable than formic acid, such as ethylene, through ongoing research.