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Angew Chem Int Ed Engl. 2019 Jun 10. doi: 10.1002/anie.201904246. [Epub ahead of print]

Highly selective photoreduction of CO2 with suppressing H2 evolution over monolayer layered double hydroxide under irradiation above 600 nm.

Author information

1
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Chemistry, Mailbox 98, Beijing University of Chemical Technology,, Beisanhuan East Road, Chaoyang District, 100029, Beijing, CHINA.
2
CHINA.
3
KOREA, REPUBLIC OF.

Abstract

Solar-driven photocatalytic reduction of CO2 into fuels and chemicals is a promising route for the storage of renewable energy. Although significant progresses have been made to improve the activity toward photocatalytic CO2 reduction under visible light (λ > 400 nm), the development of photocatalysts that can work under longer wavelength, such as irradiation with λ > 600 nm, and thus can make use of wider solar spectrum, remains to be great challenging. In this work, we reported a heterogeneous photocatalyst system that consists of ruthenium complex and monolayer nickel-alumina layered double hydroxide (NiAl-LDH), which act as light-harvesting and catalytic units for selective photoreduction of CO2 and H2O into CH4 and CO under irradiation with λ > 400 nm. Through precisely tuning the irradiation wavelength, the selectivity of CH4 can be further improved to 70.3%, and the H2 evolution reaction can be completely suppressed under irradiation with λ > 600 nm. The presence of abundant coordinately unsaturated metal defect (Ni, Al, denoted as VM) and hydroxyl defect (denoted as VOH) was confirmed by X-ray absorption fine structure etc. The spin-polarized and Hubbard corrected density functional theory calculations revealed that the defect state derived from the metal defect existed in the forbidden zone of monolayer NiAl-LDH. Under the irradiation with λ > 600 nm, the photogenerated electrons matching the energy levels of photosensitizer and m-NiAl-LDH only localized at the defect state, providing a driving force of 0.313 eV to overcome the Gibbs free energy barrier of CO2 reduction to CH4 (0.127 eV), rather than that for H2 evolution (0.425 eV). This work inspires a new insight for applying catalyst defects toward tunable selectivity for CO2 photoreduction under wider solar spectrum, facilitating the application in solar-driven CO2 conversion.

KEYWORDS:

CO2 photoreduction; Defect; H2 evolution; layered double hydroxide; visible light catalysis

PMID:
31183943
DOI:
10.1002/anie.201904246

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