skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Variation in the interface strength of silicon with surface engineered Ti 3 C 2 MXenes
Current advancements in battery technologies require electrodes to combine high-performance active materials such as Silicon (Si) with two-dimensional materials such as transition metal carbides (MXenes) for prolonged cycle stability and enhanced electrochemical performance. More so, it is the interface between these materials, which is the nexus for their applicatory success. Herein, the interface strength variations between amorphous Si and Ti 3 C 2 T x MXenes are determined as the MXene surface functional groups ( T x ) are changed using first principles calculations. Si is interfaced with three Ti 3 C 2 MXene substrates having surface −OH, −OH and −O mixed, and −F functional groups. Density functional theory (DFT) results reveal that completely hydroxylated Ti 3 C 2 has the highest interface strength of 0.6 J m −2 with amorphous Si. This interface strength value drops as the proportion of surface −O and −F groups increases. Additional analysis of electron redistribution and charge separation across the interface is provided for a complete understanding of underlying physico-chemical factors affecting the surface chemistry and resultant interface strength values. The presented comprehensive analysis of the interface aims to develop sophisticated MXene based electrodes by their targeted surface engineering.  more » « less
Award ID(s):
1911900
PAR ID:
10217359
Author(s) / Creator(s):
;
Date Published:
Journal Name:
Physical Chemistry Chemical Physics
Volume:
23
Issue:
9
ISSN:
1463-9076
Page Range / eLocation ID:
5540 to 5550
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; (, Journal of Materials Chemistry C)
    Transition metal carbides (MXenes) are an emerging family of highly conductive two-dimensional materials with additional functional properties introduced by surface terminations. Further modification of the surface terminations makes MXenes even more appealing for practical applications. Herein, we report a facile and environmentally benign synthesis of reduced Ti 3 C 2 T x MXene (r-Ti 3 C 2 T x ) via a simple treatment with l -ascorbic acid at room temperature. r-Ti 3 C 2 T x shows a six-fold increase in electrical conductivity, from 471 ± 49 for regular Ti 3 C 2 T x to 2819 ± 306 S m −1 for the reduced version. Additionally, we show an enhanced oxidation stability of r-Ti 3 C 2 T x as compared to regular Ti 3 C 2 T x . An examination of the surface-enhanced Raman scattering (SERS) activity reveals that the SERS enhancement factor of r-Ti 3 C 2 T x is an order of magnitude higher than that of regular Ti 3 C 2 T x . The improved SERS activity of r-Ti 3 C 2 T x is attributed to the charge transfer interaction between the MXene surface and probe molecules, re-enforced by an increased electronic density of states (DOS) at the Fermi level of r-Ti 3 C 2 T x . The findings of this study suggest that reduced MXene could be a superior choice over regular MXene, especially for the applications that employ high electronic conductivity, such as electrode materials for batteries and supercapacitors, photodetectors, and SERS-based sensors. 
    more » « less
  2. ; ; ; ; ; ; (, 2D Materials)
    Abstract MXenes are a new family of two-dimensional carbides and/or nitrides. Their 2D surfaces are typically terminated by O, OH and/or F atoms. Here we show that Ti3C2Tx—the most studied compound of the MXene family—is a good acid catalyst, thanks to the surface acid functionalities. We demonstrate this by applying Ti3C2Txin the epoxide ring-opening reaction of styrene oxide (SO) and its isomerization in the liquid phase. Modifying the MXene surface changes the catalytic activity and selectivity. By oxidizing the surface, we succeeded in controlling the type and number of acid sites and thereby improving the yield of the mono-alkylated product to >80%. Characterisation studies show that a thin oxide layer, which forms directly on the Ti3C2Txsurface, is essential for catalysing the SO ring-opening. We hypothesize that two kinds of acid sites are responsible for this catalysis: In the MXene, strong acid sites (both Lewis and Brønsted) catalyse both the ring-opening and the isomerization reactions, while in the Mxene–TiO2composite weaker acid sites catalyse only the ring-opening reaction, increasing the selectivity to the mono-alkylated product. 
    more » « less
  3. ; ; ; ; ; ; (, Science Advances)
    Two-dimensional (2D) transition metal carbides and nitrides, commonly known as MXenes, are a class of 2D materials with high free carrier densities, making them highly attractive candidates for plasmonic 2D materials. In this study, we use multiphoton photoemission electron microscopy (nP-PEEM) to directly image the plasmonic near fields of multilayers of the prototypical MXene, Ti3C2Tx, with mixed surface terminations (Tx = F, O, and OH). Photon-energy dependentnP-PEEM reveals a dispersive surface plasmon polariton between 1.4 and 1.9 electron volts on MXene flakes thicker than 30 nanometers and waveguide modes above 1.9 electron volts. Combining experiments with finite-difference time-domain simulations, we reveal the emergence of a visible surface plasmon polariton in MXenes, opening avenues for exploration of polaritonic phenomena in MXenes in the visible portion of the electromagnetic spectrum. 
    more » « less
  4. ; ; ; ; ; ; ; (, Advanced Materials Interfaces)
    Abstract Surface chemistry and core composition of 2D MXenes play a major role in their interfacial properties, but the determination and quantification of their bonding environments remain challenging. X‐ray Photoelectron Spectroscopy (XPS) is a method of choice that is broadly utilized but is often hindered by large uncertainties and systematic bias due to adsorbed species such as adventitious carbon or etching residues. In this work, energy‐dependent XPS and depth profile modeling of the Ti3C2TxMXene surface are employed to differentiate the contributions from the MXene and the adsorbed species, thereby increasing the accuracy of quantification. In comparison, uncorrected lab‐based XPS suffers from a systematic overestimation of Ti vacancies by 7% and an underestimation of terminal atoms, particularly F, by as much as 15%. Interestingly, it is found that a simple inelastic mean free path correction is sufficient to address the issue and reveals extremely low defects in Ti3C2TxMXene synthesized using the HF/HCl etching route. Soft X‐ray Absorption Spectroscopy (XAS), supported by Density Functional Theory (DFT) calculations, also demonstrates a high chemical sensitivity of the surface terminations. This work provides novel insights into XPS quantification and the use of XAS for probing the carbide core and surface chemistry of Ti3C2TxMXenes. 
    more » « less
  5. ; ; ; ; ; ; ; ; (, Advanced Materials Interfaces)
    Abstract Control of surface functionalization of MXenes holds great potential, and in particular, may lead to tuning of magnetic and electronic order in the recently reported magnetic Cr2TiC2Tx. Here, vacuum annealing experiments of Cr2TiC2Txare reported with in situ electron energy loss spectroscopy and novel in situ Cr K‐edge extended energy loss fine structure analysis, which directly tracks the evolution of the MXene surface coordination environment. These in situ probes are accompanied by benchmarking synchrotron X‐ray absorption fine structure measurements and density functional theory calculations. With the etching method used here, the MXene has an initial termination chemistry of Cr2TiC2O1.3F0.8. Annealing to 600 °C results in the complete loss of F, but O termination is thermally stable up to (at least) 700 °C. These findings demonstrate thermal control of F termination in Cr2TiC2Txand offer a first step toward termination engineering this MXene for magnetic applications. Moreover, this work demonstrates high energy electron spectroscopy as a powerful approach for surface characterization in 2D materials. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email