## 3 Results and Discussion
The spectra of the carbonized sponge clearly showed the absence of the structure associated with the peptide group (peak 288.1 eV) and nitrogen compounds (peak 287.6 eV). At the same time, passing from the spectrum of the native sponge to the one of carbonized sponge, a short-wave shift by 0.4 eV of the main \(\pi^{\star}\) absorption peak at energy \(\sim\)285.0 eV was observed. In the case of native sponge spectra, this peak corresponded to a C 1s \(\rightarrow\pi^{\star}\) electron transition in an aromatic ring, and for carbonized sponge, the peak position coincided with the characteristic energy of this transition for hexagons in the graphene planes of the multi-wall carbon nanotube and highly oriented pyrolytic graphite (285.4 eV) [34]. The NEXAFS data showed the carbon oxide structures on the carbonized sponge surface: a broad band at \(\sim\)287.2 eV (C-O and C-O-C groups), a peak at 288.5 eV (carbonyl group C=O), and a small peak at 290.3 eV,  
which corresponded to the anion [CO3]2\({}^{-}\) or carboxylic group HO-C=O. It follows from the XPS data that carbonized sponge as a whole contained no more than 10% carbide oxides. The C 1s and O 1s XPS spectra of the carbonized sponge are shown in Figure 2a,c,d. The C 1s XPS spectrum was fitted using three bands. The first at a BE of 284.5 eV corresponded to carbon atoms in turbostratic graphite, the second one at 286.4 eV was associated with the C-O bond of carbon atoms, and the third band at 289.6 eV was associated with the carboxyl C=O bond. This identification was well correlated with the C 1s NEXAFS data. The O 1s XPS spectrum was fitted using three peaks with BEs of 530.6 eV, 531.8 eV, and 533.0 eV. These peaks can be identified as corresponding to OH, H\({}_{2}\)O, and C-O/C=O groups, respectively [33]. On the carbonized sponge surface, the concentration of oxygen atoms in the form of carbon oxides, as well as in the form of adsorbed water molecules and hydroxyl groups, was rather high and equal to 4-5% and 5-6%, respectively. The high content of adsorbed water on the carbonized sponge surface was due to the strong roughness and high porosity of the surface [33], which can be clearly seen in the SEM image in Figure 1h. Figure 5 shows the Raman spectra of a native sponge before and after pyrolysis at 1200 \({}^{\circ}\)C in argon. The sharp changes in the structure of the spectra clearly demonstrated the phenomena of graphitization during pyrolysis. The dramatic changes in the structure of the spectra in the transition from the sponge before and after pyrolysis can be clearly seen in Figure 5. The spectrum of the native sponge was distorted due to the strong fluorescence of the sample and the vibrational structure was extremely low contrast. However, the D, G, and 2D bands appeared in the spectrum of the carbonized sponge. The wavenumber positions of these bands and the ratio of the band areas (D/G) were analyzed by us in [21] using the Ferrari and Robertson model [60]. It was shown that pyrolysis of the sponge involves clustering and formation of sp2 bonds; the material transforms from amorphous carbon to nanocrystalline graphite with increasing temperature and contains mixed sp2 and sp3 bond centers. In the case of marine sponge carbonized at 1200 \({}^{\circ}\)C, the average size of graphite nanocrystallites is about 3 nm.