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Monolayers of Ti3C2Tx MXene and bilayer structures formed by partially overlapping monolayer flakes exhibit opposite sensing responses to a large scope of molecular analytes. When exposed to reducing analytes, monolayer MXene flakes show increased electrical conductivity, i.e., an n-type behavior, while bilayer structures become less conductive, exhibiting a p-type behavior. On the contrary, both monolayers and bilayers show unidirectional sensing responses with increased resistivity when exposed to oxidizing analytes. The sensing responses of Ti3C2Tx monolayers and bilayers are dominated by entirely different mechanisms. The sensing behavior of MXene monolayers is dictated by the charge transfer from adsorbed molecules and the response direction is consistent with the donor/acceptor properties of the analyte and the intrinsic n-type character of Ti3C2Tx. In contrast, the bilayer MXene structures always show the same response regardless of the donor/acceptor character of the analyte, and the resistivity always increases because of the intercalation of molecules between the Ti3C2Tx layers. This study explains the sensing behavior of bulk MXene sensors based on multiflake assemblies, in which this intercalation mechanism results in universal increase in resistance that for many analytes is seemingly inconsistent with the n-type character of the material. By scaling MXene sensors down from multiflake to single-flake level, we disentangled the charge transfer and intercalation effects and unraveled their contributions. In particular, we show that the charge transfer has a much faster kinetics than the intercalation process. Finally, we demonstrate that the layer-dependent gas sensing properties of MXenes can be employed for the design of sensor devices with enhanced molecular recognition.
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Ti3C2Tx MXene-Based Hybrid Photocatalysts in Organic Dye Degradation: A Review
This review provides an overview of the fabrication methods for Ti3C2Tx MXene-based hybrid photocatalysts and evaluates their role in degrading organic dye pollutants. Ti3C2Tx MXene has emerged as a promising material for hybrid photocatalysts due to its high metallic conductivity, excellent hydrophilicity, strong molecular adsorption, and efficient charge transfer. These properties facilitate faster charge separation and minimize electron–hole recombination, leading to exceptional photodegradation performance, long-term stability, and significant attention in dye degradation applications. Ti3C2Tx MXene-based hybrid photocatalysts significantly improve dye degradation efficiency, as evidenced by higher percentage degradation and reduced degradation time compared to conventional semiconducting materials. This review also highlights computational techniques employed to assess and enhance the performance of Ti3C2Tx MXene-based hybrid photocatalysts for dye degradation. It identifies the challenges associated with Ti3C2Tx MXene-based hybrid photocatalyst research and proposes potential solutions, outlining future research directions to address these obstacles effectively.
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- Award ID(s):
- 2122044
- PAR ID:
- 10582790
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Molecules
- Volume:
- 30
- Issue:
- 7
- ISSN:
- 1420-3049
- Page Range / eLocation ID:
- 1463
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3390/molecules30071463
