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

ABSTRACT: We describe the synthesis and visible-light CO₂ photoreduction catalytic properties of a three-component composite consisting of AgI, AgIO₃, and single-walled carbon nanotubes (SWCNTs). The catalyst is synthesized by immersing SWCNTs encapsulating iodine molecules in AgNO₃ aqueous solution, during which neutral iodine (I₂) molecules encapsulated in SWCNTs transform disproportionately to I⁵⁺ (AgIO₃) 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 CO₂ photoreduction catalyst under visible light despite the wide band gap of AgIO₃, suggesting possible transfer of the visible light-excited electron from AgI via SWCNTs.

SUBMITTER: Al-Zubaidi A

PROVIDER: S-EPMC8115251 | biostudies-literature | 2021 May

REPOSITORIES: biostudies-literature

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

Al-Zubaidi Ayar A Kobayashi Kenta K Ishii Yosuke Y Kawasaki Shinji S

Scientific reports 20210512 1

We describe the synthesis and visible-light CO2 photoreduction catalytic properties of a three-component composite consisting of AgI, AgIO3, and single-walled carbon nanotubes (SWCNTs). The catalyst is synthesized by immersing SWCNTs encapsulating iodine molecules in AgNO3 aqueous solution, during which neutral iodine (I2) molecules encapsulated in SWCNTs transform disproportionately to I5+ (AgIO3) and I- (AgI), as reve ...[more]

PMID: 33980949

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Project description:Solar-light driven reduction of CO2 to CH4 is a complex process involving multiple electron and proton transfer processes with various intermediates. Therefore, achieving high CH4 activity and selectivity remains a significant challenge. Covalent organic frameworks (COFs) represent an emerging class of photoactive semiconductors with molecular level structural tunability, modular band gaps, and high charge carrier generation and transport within the network. Here, we developed a new heterocyclic triazole ring containing COF, TFPB-TRZ, through the condensation reaction between 1,3,5-tris(4-formylphenyl)benzene (TFPB) and 3,5-diamino-1,2,4-triazole (TRZ). The TFPB-TRZ COF with multiple heteroatoms shows suitable visible light absorption, high CO2 uptake capability and an appropriate band diagram for CO2 photoreduction. Photocatalysis results reveal a maximum CO2 to CH4 conversion of 2.34 mmol g-1 with a rate of 128 μmol g-1 h-1 and high selectivity (∼99%) using 1-benzyl-1,4-dihydronicotinamide (BNAH) and triethylamine (TEA) as sacrificial agents. Under similar reaction conditions in the presence of direct sunlight, the TFPB-TRZ COF displays a maximum CH4 yield of 493 μmol g-1 with a rate of 61.62 μmol g-1 h-1, suggesting the robustness and light-harvesting ability of the COF photocatalyst. A femtosecond transient absorption (TA) spectroscopy study shows fast decay of excited state absorption (ESA) in the COF compared to the TFPB building unit due to efficient electron transfer to the catalytic site in the framework. The mechanism of CO2 reduction to CH4 is studied by DFT-based theoretical calculation, which is further supported by an in situ diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) study. The DFT results reveal that the lone pair of electrons on nitrogen heteroatoms present in the triazole ring of the TRZ moiety help in the stabilization of the CO intermediate during CO2 to CH4 conversion. Overall, this work demonstrates the use of a metal-free, recyclable COF-based photocatalytic system for solar energy storage by CO2 reduction.

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

Publications

One-step synthesis of visible light CO<sub>2</sub> reduction photocatalyst from carbon nanotubes encapsulating iodine molecules.

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