Only when the interfacial charge separation is enhanced and the CO 2 activation is improved, can the heterojunction nanocomposite photocatalyst be brought into full play for the CO 2 reduction reaction (CO 2 RR). Here, Er 3+ single atom composite photocatalysts were successfully constructed based on both the special role of Er 3+ single atoms and the special advantages of the SrTiO 3 :Er 3+ /g-C 3 N 4 heterojunction in the field of photocatalysis for the first time. As we expected, the SrTiO 3 :Er 3+ /g-C 3 N 4 (22.35 and 16.90 μmol g −1 h −1 for CO and CH 4 ) exhibits about 5 times enhancement in visible-light photocatalytic activity compared to pure g-C 3 N 4 (4.60 and 3.40 μmol g −1 h −1 for CO and CH 4 ). In particular, the photocatalytic performance of SrTiO 3 :Er 3+ /g-C 3 N 4 is more than three times higher than that of SrTiO 3 /g-C 3 N 4 . From Er 3+ fluorescence quenching measurements, photoelectrochemical studies, transient PL studies and DFT calculations, it is verified that a small fraction of surface doping of Er 3+ formed Er single-atoms on SrTiO 3 building an energy transfer bridge between the interface of SrTiO 3 and g-C 3 N 4 , resulting in enhanced interfacial charge separation. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) and adsorption energy calculations demonstrated that the exposed Er single-atoms outside the interface on SrTiO 3 preferentially activate the adsorbed CO 2 , leading to the high photoactivity for the CO 2 RR. A novel enhanced photocatalytic mechanism was proposed, in which Er single-atoms play dual roles of an energy transfer bridge and activating CO 2 to promote charge separation. This provides new insights and feasible routes to develop highly efficient photocatalytic materials by engineering rare-earth single-atom doping.
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Concentrate and Degrade Pfoa with a Photo-Regenerable Composite of In-Doped Tnts@Ac
“Concentrate-and-degrade” is an effective strategy to promote mass transfer and degradation of pollutants in photocatalytic systems, yet suitable and cost-effective photocatalysts are required to practice the new concept. In this study, we doped a post-transition metal of Indium (In) on a novel composite adsorptive photocatalyst, activated carbon-supported titanate nanotubes (TNTs@AC), to effectively degrade perfluorooctanoic acid (PFOA). In/TNTs@AC exhibited both excellent PFOA adsorption (>99% in 30 min) and photodegradation (>99% in 4 h) under optimal conditions (25 °C, pH 7, 1 atm, 1 g/L catalyst, 0.1 mg/L PFOA, 254 nm). The heterojunction structure of the composite facilitated a cooperative adsorption mode of PFOA, i.e., binding of the carboxylic head group of PFOA to the metal oxide and attachment of the hydrophobic tail to AC. The resulting side-on adsorption mode facilitates the electron (e‒) transfer from the carboxylic head to the photogenerated hole (h+), which was the major oxidant verified by scavenger tests. Furthermore, the presence of In enables direct electron transfer and facilitates the subsequent stepwise defluorination. Finally, In/TNTs@AC was amenable to repeated uses in four consecutive adsorption-photodegradation runs. The findings showed that adsorptive photocatalysts can be prepared by hybridization of carbon and photoactive semiconductors and the enabled “concentrate-and-degrade” strategy is promising for the removal and degradation of trace levels of PFOA from polluted waters.
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- Award ID(s):
- 2041060
- NSF-PAR ID:
- 10334623
- Date Published:
- Journal Name:
- SSRN Electronic Journal
- Volume:
- 300
- ISSN:
- 1556-5068
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.2139/ssrn.3989405
