Fig.3.
(a) Raman spectra of MXene, MXene/AAC and AAC; (b) XRD imaged of MXene,
MXene/AAC and AAC; (c) Nitrogen adsorption isotherms of MXene and
MXene/AAC 2:1; (d) Pore size distribution of MXene and MXene/AAC 2:1;
(e) C 1s spectra of MXene/AAC 2:1;(f) Ti 2p spectra of MXene/AAC 2:1
In order to confirm that the enhanced interlayer spacing observed in ATM
is statistically significant. X-ray diffraction (XRD) patterms are
performed for pure MXene, MXene/AAC 5:1, MXene/AAC 2:1 and AAC
composites and shown in Fig.3. (b). The MXene film exhibits a peak (002)
at about 2θ=7.5°, corresponding to d-spacing values of 12.62 Å. The
peaks corresponding to the (002) plane of MXene/AAC 2:1 and MXene/AAC
5:1 downshift to about 2θ=7.06° and 2θ=6.07° which demonstrates a 3.0 Å
and 4.2 Å in the c -lattice parameter (c -LP) and 1.5 Å and
2.1 Å increase the d -spacing, respectively. In the pure AAC, a
broad peak at 2θ=25° is observed, demonstrating exceptional
graphitization, which further proved the stability of the composite
after chemical treatment. In addition, the
intensity of (002) peaks decreases
with the increase of AAC content, indicating that the order between
MXene layers is interrupted due to hybridization with AAC. Besides, all
MXene/AAC composites have the broad peak (002) of AAC particles which
confirms manufacturing of MXene/AAC. However, the intercalation of AAC
into MXene layers could reduce material density and electrical
conductivity. As shown in Table S1. The MXene composite has an
electrical conductivity of 3206 S cm-1 and a material
density of 2.01 g cm-3. Nevertheless, the electrical
conductivity and material density decrease with the increase of AAC mass
ratio. Besides, the MXene/AAC 2:1 and MXene/AAC 5:1 exhibit a quite low
material density of 0.309 and 0.406 g cm-3 with the
electrical conductivity of 191 and 357 S cm-1,
respectively. In contrast, with the increase of AAC mass ratio, the
specific surface area (BET) and specific volume (Vtotal)
of MXene/AAC increase. The pure MXene shows a much lower BET (18.92
m2g-1) and Vtotal(0.008 cm3g-1) than MXene/AAC 2:1
hybrid (1651 m2g-1 and 1.07
cm3g-1). Due to the large surface
areas and abundant specific volume, the electrochemical performance of
MXene/AAC are greatly enhanced.
The microstructure and exposed surface area of the as-prepared hybrid
are examined by the nitrogen (77K) adsorption-desorption measurement.
Fig.3. (c-d) show the nitrogen adsorption isotherms and pore size
distributions of pure MXene and MXene/AAC 2:1. The MXene/AAC 2:1
particles present a combination of type-Ⅰ and type-Ⅱ isotherms,
demonstrating that the microporous-mesoporous structure which could be
ascribed to the incorporation of AAC between MXene layers. Fig.3. (a)
presents Raman spectra of the pure MXene and MXene/AAC composite. The
Raman spectra of MXene and MXene/AAC are similar in the range of 100 to
800 cm-1. The MXene has a sharp peak at about 150
cm-1 and broad peaks at about 370
cm-1 and 619 cm-1, which are
distinctive feature of MXene. On the other hand, the peaks at about 1275
and 1572 cm-1 represent as the D-band and G-band,
respectively which are signatures of carbon and confirm the
incorporation of MXene and AAC. The D-band corresponds to defects and
relates to zone boundary k -point phonons and the G-band is due to
collective symmetric stretching of sp2 carbon lattice.
The ratio of the D-band and G-band
(I D/I G) which proportional
to the defect sites in graphitic carbon is 1.29 which could calculate
the corresponding sp2 crystallite size to be 9.8 nm
according to the followed formula.
\(L_{a}\left(\text{nm}\right)=560/E_{\text{laser}}^{4}(\frac{I_{D}}{I_{G}})\)-1(6)
Where \(L_{a}\) is the average sp2 crystallite size,E laser is the laster excitation energy in eV.
In order to further investigate the mechanism and chemical compositions
of synthesized MXene/AAC interaction, X-ray photoelectron spectroscopy
(XPS) was employed to examine the chemical composition and surface
electronic states and the corresponding images exhibited in Fig.3. (c-d)
and Fig. S3 (a-c). The XPS survey spectra as shown in Fig. S3 (a)
demonstrate that the MXene/AAC hybrids are mainly composed of C, Ti, O,
N and F. High-resolution XPS
spectrum in the Ti 2p region (Fig.3. (d)) core levels of MXene/AAC 2:1
hybrids could be deconvoluted into six peaks with components
corresponding to Ti-C, Ti(Ⅱ), Ti(Ⅲ) and Ti-O peaks. The Ti 2p core level
can be fitted with three doublets (Ti 2p3/2-Ti
2p1/2) which in agreement with other papers(尚). The Ti
2p3/2 components mainly located at binding energy of
458.6, 459.1, 463.3 and 464.9 eV correspond to Ti-C
2p3/2, Ti-O 2p3/2,
C-Ti-Tx 2p1/2 and Ti-O
2p1/2, respectively, demonstrating the interaction
between MXene and AAC particles at the sites of oxygen dangling bonds.
However, the XRD spectrum exhibits no peaks for TiO2.The Raman pattern of MXene/AAC exhibits similar vibrations in the shift
range 100-800 cm-1, demonstrating that the appearance
of Ti-O peak mainly comes from the MXene-to-AAC contact
area31, 32. The C 1s core level (Fig.3. (c)) could be
fitted with five components at binding energy of 284.1, 284.8, 286.3,
286.6, and 288.9 eV, which could be assigned to C-Ti-O, Ti-O, C-C, C-N,
C-O and O=C-O bonds, respectively. confirming the interaction between
MXene layers and AAC particles33, 34. Fig.S3. (b)
exhibits the N 1s core level mainly centered at binding energy of 397.6,
398.8 and 399.9 eV which could be accordingly assigned to Ti-N,
pyridinic N and pyrrolic N, respectively. Fig.S3. (c) exhibits the O 1s
core level which could be fitted with three components at binding energy
of 530.4, 531.8 and 532.9 eV which further confirm the interaction
between MXene flake and AAC particles. The result is in good agreement
with the TEM observation.