Photocatalytic conversion of CO2 in water using fluorinated layered double hydroxides as photocatalysts

• Fluorinated M2+–Al LDH (M2+ = Mg2+ or Ni2+) was prepared via a conventional co-precipitation method using Na3AlF6 as a fluorine source.
• Fluorinated M2+–Al LDH (M2+ = Mg2+ or Ni2+) exhibited the photocatalytic activity for the conversion of CO2 in water, and the amount of CO evolved for the fluorinated LDH was larger than that for the bare LDH.
• The fluorination of LDH by incorporation of AlF63− units in hydroxide sheets afford surface properties suitable for the photocatalytic conversion of CO2 in an aqueous solution of NaCl.

The photocatalytic conversion of CO2, which can convert CO2 into useful chemicals, such as CH4, CH3OH, HCOOH, HCHO, and CO, is attractive process for creating an artificial carbon cycling system. It was found that the synthetic Ni–Al layered double hydroxide (Ni–Al LDH) can reduce CO2 into CO in an aqueous solution of NaCl under UV light irradiation, and chloride ions (Cl−) in the reaction solution scavenge the photogenerated holes. In this study, we prepared fluorinated Mg–Al LDH and Ni–Al LDH for altering the chemical and/or physical properties of the LDH as a solid base, and investigated the effect of fluorination on the photocatalytic activity for the conversion of CO2 in an aqueous solution. We found that the fluorination of LDH by incorporation of hexafluoroaluminate (AlF63−) units in the hydroxide sheets clearly improved the amount of CO evolved as a reduction product of CO2.

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