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In the account by Attard et al. [12], N‐doped Starbon produced by either the inclusion of chitosan or ammonia displayed similar characteristics. A significant amount of nitrile was observed in these materials, something that was known to be unusual in other forms of N‐doped carbons [12]. The TGIR results showed that chitosan released ammonia upon heating to low temperatures, whereas N‐Starbon did not. It was concluded that the amine groups in chitosan may become trapped in the form of nitriles, the presence of which was confirmed by a DRIFT absorbance band at 2210 cm⁻¹. The nitrile was assumed chemically bonded to the Starbon as it remained present after generous washing with ethanol and water.

The presence of nitriles was further explored by preparing a range of materials and it was found that nitriles only form at carbonisation temperatures above 300 °C. It was also shown that the combination of chitosan and polysaccharide precursor to Starbon was necessary to retain the mesoporous structure of the N‐doped materials, as chitosan alone collapsed to a microporous structure on carbonisation.

Porosimetry was carried out on N‐Starbon from each synthetic route, showing that N‐doping did not negatively influence mesoporosity. Route A, using a chitosan/polysaccharide combination, resulted in larger pore volumes and surface areas than the ammonia adsorption method. A summary of BET surface area studies and pore volume is shown in Table 3.2.

A large amount of nitrogen was detected in all samples, as confirmed by elemental analysis and XPS, and displayed in Table 3.3.

In a study to produce N‐Starbon for the application of carbon capture, Sreedhar et al. found that higher carbonisation temperatures of 750 °C for a duration of six hours were required to achieve the high surface areas and pore volumes needed [22]. Different weight loadings of monoethanolamine (10, 20, and 30%) were characterised by FTIR, with amine signals being present at 1650–1550 cm⁻¹. Further studies by X ray diffraction (XRD) confirmed that N‐Starbons from both corn and potato starch were amorphous materials with very little difference between them.

Table 3.2 Textural properties of N‐doped Starbon compared with N‐free analogues.

Source: Data from Attard et al. [12].

Carbonisation temp. (°C)	Material	Mesoporosity (%)	Total pore volume (cm3 g−1)	BET surface area (m2 g−1)
300	Starbon N‐Starbon‐A N‐Starbon‐B	88.3 86.7 98.7	0.627 0.663 0.645	174.2 412.6 240.5
450	Starbon N‐Starbon‐A	84.5 81.9	0.515 0.615	339.5 448.3
600	Starbon N‐Starbon‐A N‐Starbon‐C	79.8 83.5 92.8	0.686 0.750 0.324	519.5 519.2 249.5

Table 3.3 Nitrogen content of N‐doped Starbons.

Source: Data from Attard et al. [12].

Carbonisation temp. (°C)	Nitrogen content (wt%)	C/N ratio
CHN	XPS	CHN	XPS
300‐A	6.4	4.9	9.2	15.3
300‐B	6.8	6.1	8.8	12.4
450‐A	10.6	11.6	5.7	5.8
600‐A	6.5	7.0	11.1	11.3
600‐C	12.4	12.9	5.8	5.9