Investigating the Role of Tunable Nitrogen Vacancies in Graphitic Carbon Nitride Nanosheets for Efficient Visible-Light-Driven H2 Evolution and CO2 Reduction

Wenguang Tu, You Xu, Jiajia Wang, Bowei Zhang, Tianhua Zhou, Shengming Yin, Shuyang Wu, Chunmei Li, Yizhong Huang, Yong Zhou, Zhigang Zou, John Robertson, Markus Kraft, Rong Xu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

376 Citations (Scopus)

Abstract

Vacancy engineering, that is, self-doping of vacancy in semiconductors, has become a commonly used strategy to tune the photocatalytic performances. However, there still lacks fundamental understanding of the role of the vacancies in semiconductor materials. Herein, the g-C3N4 nanosheets with tunable nitrogen vacancies are prepared as the photocatalysts for H2 evolution and CO2 reduction to CO. On the basis of both experimental investigation and DFT calculations, nitrogen vacancies in g-C3N4 induce the formation of midgap states under the conduction band edge. The position of midgap states becomes deeper with the increasing of nitrogen vacancies. The g-C3N4 nanosheets with the optimized density of nitrogen vacancies display about 18 times and 4 times enhancement for H2 evolution and of CO2 reduction to CO, respectively, as compared to the bulk g-C3N4. This is attributed to the synergistic effects of several factors including (1) nitrogen vacancies cause the excitation of electrons to midgap states below the conduction band edge, which results in extension of the visible light absorption to photons of longer wavelengths (up to 598 nm); (2) the suitable midgap states could trap photogenerated electrons to minimize the recombination loss of photogenerated electron-hole pairs; and (3) nitrogen vacancies lead to uniformly anchored small Pt nanoparticles (1-2 nm) on g-C3N4, and facilitate the electron transfer to Pt. However, the overintroduction of nitrogen vacancies generates deeper midgap states as the recombination centers, which results in deterioration of photocatalytic activities. Our work is expected to provide new insights for fabrication of nanomaterials with suitable vacancies for solar fuel generation.

Original languageEnglish
Pages (from-to)7260-7268
Number of pages9
JournalACS Sustainable Chemistry and Engineering
Volume5
Issue number8
DOIs
Publication statusPublished - Aug 7 2017
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.

ASJC Scopus Subject Areas

  • General Chemistry
  • Environmental Chemistry
  • General Chemical Engineering
  • Renewable Energy, Sustainability and the Environment

Keywords

  • g-CN
  • Midgap states
  • Nitrogen vacancy
  • Photocatalysis

Fingerprint

Dive into the research topics of 'Investigating the Role of Tunable Nitrogen Vacancies in Graphitic Carbon Nitride Nanosheets for Efficient Visible-Light-Driven H2 Evolution and CO2 Reduction'. Together they form a unique fingerprint.

Cite this