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Indexed by:期刊论文

Date of Publication:2019-04-01

Journal:CHEMISTRY-A EUROPEAN JOURNAL

Included Journals:PubMed、EI、SCIE

Volume:25

Issue:19

Page Number:5028-5035

ISSN No.:0947-6539

Key Words:carbon nitride; N defects; photochemistry; CO2 reduction

Abstract:Fundamental photocatalytic limitations of solar CO2 reduction remain due to low efficiency, serious charge recombination, and short lifetime of catalysts. Herein, two-dimensional graphitic carbon nitride nanosheets with nitrogen vacancies (g-C3Nx) located at both three-coordinate N atoms and uncondensed terminal NHx species were prepared by one-step tartaric acid-assistant thermal polymerization of dicyandiamide. Transient absorption spectra revealed that the defects in g-C3N4 act as trapped states of charges to result in prolonged lifetimes of photoexcited charge carriers. Time-resolved photoluminescence spectroscopy revealed that the faster decay of charges is due to the decreased interlayer stacking distance in g-C3Nx in favor of hopping transition and mobility of charge carriers to the surface of the material. Owing to the synergic virtues of strong visible-light absorption, large surface area, and efficient charge separation, the g-C3Nx nanosheets with negligible loss after 15 h of photocatalysis exhibited a CO evolution rate of 56.9 mu mol g(-1) h(-1) under visible-light irradiation, which is roughly eight times higher than that of pristine g-C3N4. This work presents the role of defects in modulating light absorption and charge separation, which opens an avenue to robust solar-energy conversion performance.