One-step synthesis of visible light CO(2) 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.