Efficient visible and NIR light-driven photocatalytic CO2 reduction over defect-engineered ZnO/carbon dot hybrid and mechanistic insights

Liang-Yi Lin*, Chieh Liu, Tsung Ta Hsieh

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

Photocatalytic CO2 reduction with H2O over wide bandgap semiconductor-based photocatalysts is significantly limited by the low light utilization efficiency and poor activation of CO2/H2O molecules on the photocatalyst's surface. Herein, we demonstrate that oxygen-deficient ZnO/carbon dot (OD-ZnO/C) hybrid, rationally engineered with synergistically enhanced CO2/H2O activation ability and increased light utilization efficiency, showed excellent full spectrum (UV, visible and NIR light)-driven CO2 photoreduction. Under UV–Vis-NIR, Vis-NIR and NIR light separately, the optimized sample demonstrated high quantum yields of 0.26%, 0.13% and 0.05% for CO production, yields which are considerably superior to the reported values in the literature. The synergistic effects between OD-ZnO and carbon dots for visible- and NIR-driven CO2 reduction were systematically investigated. Experimental results showed that both the defect-induced sub-band in OD-ZnO and the upconverting emission from the carbon dots effectively increased the light utilization efficiency within the UV–Vis to NIR region, and the heterojunctions formed between OD-ZnO and carbon dots promoted the efficient separation of charge carriers. Meanwhile, the defect-rich surface ensures the efficient adsorption and activation of CO2/H2O into the key intermediate CO2, formate, and hydroxyl species, which are effectively converted under light illumination from UV–Vis to NIR region. Based on the combined results of the CO2 photoreduction analysis and the material characterization, plausible CO2 photoreduction pathways under visible and NIR light irradiation are proposed.

Original languageAmerican English
Pages (from-to)298-311
Number of pages14
JournalJournal of Catalysis
Volume391
DOIs
StatePublished - Nov 2020

Keywords

  • Carbon dot
  • CO reduction
  • Full solar spectrum photocatalysis
  • Oxygen defect
  • ZnO

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