One-step synthesis of visible light CO2 reduction photocatalyst from carbon nanotubes encapsulating iodine molecules

We describe the synthesis and visible-light CO 2 photoreduction catalytic properties of a three-component composite consisting of AgI, AgIO 3 , and single-walled carbon nanotubes (SWCNTs). The catalyst is synthesized by immersing SWCNTs encapsulating iodine molecules in AgNO 3 aqueous solution, during which neutral iodine (I 2 ) molecules encapsulated in SWCNTs transform disproportionately to I 5+ (AgIO 3 ) and I − (AgI), as revealed from the characterization of the composite by Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In addition, photoirradiation experiments using a solar-simulator (AM1.5G) showed that the obtained three-component composite works as a CO 2 photoreduction catalyst under visible light despite the wide band gap of AgIO 3 , suggesting possible transfer of the visible light-excited electron from AgI via SWCNTs.