Researchers use fluorine doping methods to design catalysts with improved performance

Researchers use fluorine doping methods to design catalysts with improved performance

Researchers use fluorine-doping method to construct catalysts with enhanced performance The in-situ F-doped Fe-NC catalyst retains the advantage of low over-potential of Fe-NC, with greatly increased CO faradical efficiency and partial current density due to the stabilized Fe3+ active sites by electron withdrawing F-doping. Credit: Nanoscience

As the industry has developed over the last century, excess carbon dioxide emissions have led to climate problems and greenhouse effects. Researchers are constantly working on solutions to the problems of greenhouse gases, which heat the earth’s surface and the lower parts of the atmosphere. Carbon dioxide is the most common of the greenhouse gases.

Carbon dioxide can be electrochemically reduced to valuable chemicals using wind or sunlight-derived electrical energies. This carbon dioxide reduction presents researchers with a promising strategy for dealing with balance on a global scale. Electrochemical reduction of carbon dioxide offers future potential to convert carbon dioxide into useful, more environmentally friendly chemicals, such as carbon monoxidemethane or ethanol. To achieve carbon dioxide reduction, researchers need efficient electrocatalysts. Electrocatalysts are the catalysts used in electrochemical reactions. They can increase the speed of the reaction that occurs. A research team from Nanjing University has designed catalysts using a fluorine doping method that improves their performance.

The research group reported their results in Nanoscience.

Researchers know that cheap metal-nitrogen-carbon catalysts in one place work well for electroreduction of carbon dioxide to carbon monoxide. Among these, the nickel-nitrogen-doped carbon single-site catalysts have the high faradaic efficiency of carbon monoxide and high partial flow. The faradaic efficiency describes how efficiently charge is transferred in an electrochemical reaction.

The research team has already increased the faradaic efficiency and the large partial flow of nickel-nitrogen-doped carbon-site catalysts by doping them. Compared to the nickel-nitrogen doped carbon-sing site catalysts, iron-nitrogen-carbon-single-site catalysts have lower overpotentials for carbon dioxide electroreduction. Overpotential describes the voltage efficiency of a cell. Previous research has used fine structure spectroscopy with X-ray absorption to verify that the active sites of the iron-nitrogen-carbon catalysts are Fe3+ websites. These Fe3+ websites allow catalyst to be more efficient in carbon dioxide adsorption and carbon monoxide desorption.

The team designed a fluorine-doped iron-nitrogen-carbon single-site catalyst that has more Fe3+ websites, as they expected. The fluorinated doped iron-carbon single-site catalyst they designed retained the advantage of low overpotential. It also promoted the efficiency of the faradaic carbon monoxide from a volcano-like high value to a high plateau value. “The results indicate the superior stability of fluorine-doped iron-nitrogen carbon to iron-nitrogen carbon due to fluoride doping,” said Lijun Yang, an associate professor at the School of Chemistry and Chemical Engineering, Nanjing University.

The research team concludes that the electron-withdrawing fluorine doping enables the iron-nitrogen-carbon catalyst to maintain the advantage of low overpotential, with a much increased faradic carbon monoxide efficiency and partial current density due to the stabilized Fe3+ websites.

The team synthesized iron-nitrogen-carbon using a heating method called adsorption pyrolysis. They performed carbon dioxide reduction experiments in an H-type cell and a gas diffusion electrode cell. They used theoretical calculations to further understand the improvements that happened with fluoride doping.

“Electrochemical tests show that the enriched defects by fluoride doping kinetically increase the electroactive surface and improve the charge transfer,” says Yang. When we look forward to further studies, the research group’s results provide a simple and controllable strategy for improvement carbon dioxide electroreduction to carbon monoxide performance of iron-nitrogen-carbon catalysts by stabilizing Fe3+ websites.

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More information:
Yiqun Chen et al, Increasing the Faradaic Efficiency of CO2 Electroreduction to CO for Fe − N − C Catalysts in One Site by Stabilizing Fe3 + Sites via F-Doping, Nanoscience (2022). DOI: 10.1007 / s12274-022-4441-0

Provided by Tsinghua University Press

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