fig2

Figure 2. Phase characterization of the materials. (A) XRD patterns, and (B) Raman spectra of NDPCs. (C) XPS C 1s spectra and (D) O 1s spectra of DPC and NDPC-0.5. (E) XPS N 1s spectra of NDPCs. (F) Contents of oxygen components from XPS O 1s spectra of precursor and NDPCs. (G) Contents of nitrogen components from the XPS N 1s spectra of NDPCs.