Figure 4. (a) XRD patterns of PPyćZMO and ZMOP-x; (b) Infrared
spectra of ZMO and ZMOP-x
The constituent elements and valence state of ZMOP-4 composites were
further determined by XPS. As Figure 5a shows, the XPS full
spectrum of ZMOP-4 is displayed, and it is clear that the distribution
of C, N, O, Mn, Zn, and others. The contents of different elements of
ZMO and ZMOP-4 are compared in Figure 5b . It is obvious that
the content of the N element of ZMOP-4 is 1.77%, and the content of the
O element is also slightly increased compared with ZMO, indicating the
successful addition of PPy. In the O 1s region (in Figure 5c) ,
there are three distinct peaks at 529.9, 530.8, and 532.1 eV, which are
identified as various oxygen-bonded structures: H-O-H, Mn-O-H, and
Mn-O-Mn. Due to the small content of PPy, the content of the N element
in ZMOP-4 is only 0.85 wt.%. During the hydrothermal reaction, the
presence of nitrogen in PPy significantly enhances the electronic
conductivity of the prepared electrodes. It offers active sites that
reduce the band gap and boost the diffusion mechanism of
Zn2+, thereby contributing to the enhancement of
electronic conductivity and surface capacitance (Figure 5d ).Figure 5e indicates the spectra of Zn 2p, and the strong peaks
at 1045.0 eV, and 1022.4 eV belong to Zn2+2p1/2 and Zn2+ 2p3/2,
respectively. The gap between the two peaks is 22.6 eV, indicating that
the valence state of Zn is +2.27-29 Figure 5f shows the spectrum picture of Mn 2p. The binding energy during the Mn
2p3/2 and Mn 2p1/2 bimodal peaks is 11.5
eV, demonstrating that the main oxidation status of Mn is +3. Which is
completely aligned with the reported oxidation state of
MnO2.30 In summary, the composition
and oxidation state of Mn in ZMOP-4 composites after Zn embedding can be
determined, which is conducive to enhancing the stability and properties
of tunneled ZnxMnO2. In addition, the
corresponding fitting peak binding energy is slightly different from the
standard value, which is attributed to the impact of Mn and N
atoms.31 By all the XPS diagrams, the ZMOP composites
can be further confirmed.