Tuning the Acid/Base Properties of Nanocarbons by Functionalization via Amination

Abstract

The surface chemical properties and the electronic properties of vapor grown carbon nanofibers (VGCNFs) have been modified by treatment of the oxidized CNFs with NH(3). The effect of treatment temperature on the types of nitrogen functionalities introduced was evaluated by synchrotron based X-ray photoelectron spectroscopy (XPS), while the impact of the preparation methods on the surface acid-base properties was investigated by potentiometric titration, microcalorimetry, and zeta potential measurements. The impact of the N-functionalization on the electronic properties was measured by THz-Time Domain spectroscopy. The samples functionalized via amination are characterized by the coexistence of acidic and basic O and N sites. The population of O and N species is temperature dependent. In particular, at 873 K nitrogen is stabilized in substitutional positions within the graphitic structure, as heterocyclic-like moieties. The surface presents heterogeneously distributed and energetically different basic sites. A small amount of strong basic sites gives rise to a differential heat of CO(2) adsorption of 150 kJ mol(-1). However, when functionalization is carried out at 473 K, nitrogen moieties with basic character are introduced and the maximum heat of adsorption is significantly lower, at approximately 90 kJ mol(-1). In the latter sample, energetically different basic sites coexist with acidic oxygen groups introduced during the oxidative step. Under these conditions, a bifunctional acidic and basic surface is obtained with high hydrophilic character. N-functionalization carried out at higher temperature changes the electronic properties of the CNFs as evaluated by THz-TDS. The functionalization procedure presented in this work allows high versatility and flexibility in tailoring the surface chemistry of nanocarbon material to specific needs. This work shows the potential of the N-containing nanocarbon materials obtained via amination in catalysis as well as electronic device materials.

Atomic-scale characterization of nitrogen-doped graphite: Effects of dopant nitrogen on the local electronic structure of the surrounding carbon atoms

“…Four N 1s peak components at 398.5, 399.9, 401.1, and 403.2 eV have been assigned to pyridinic-N (N connected to two C), pyrrolic-N (N part of a pentagon ring connected to two C), graphitic-N (N connected to three C), and oxide-N species, respectively. 6,[27][28][29] Here, the energy position for pyrrolic-N is known to be similar to that for cyanide-N (N connected to a single C, 399.5 eV) and amine-N (N connected to a single C and two H, 399.4 eV), 27 possibly also contributing to the same peak. In our samples, pyridinic-N and graphitic-N were the dominant components, as shown in Fig.…”

“…20,21 By x-ray photoelectron spectroscopy (XPS), the nitrogen species in N-doped graphite materials 12,13,15,19,[22][23][24][25][26] have been identified mainly as pyridinic-N (characterized by a binding energy of ∼398.5 eV), pyrrolic-N (400.5 eV), and graphitic-N or quaternary-N (401.2 eV). 6,[27][28][29] However, a detailed picture of the local electronic modifications in N-doped graphite induced by each of N atoms has not been clarified.…”

Selective Oxidation of Raw Glycerol Using Supported AuPd Nanoparticles

“…NaAuCl4 2H2O and Na2PdCl4 were from Aldrich (99.99% purity), activated carbon from Camel (X40S; SA = 900-1100 m 2 /g; PV = 1.5 mL/g; pH 9-10), commercial carbon nanotubes, Baytubes (average diameter of 10 ± 2 nm and a specific surface area of 288 m 2 /g), from Bayer, commercial CNFs PR24-PS from Applied Science (average diameter of 88 ± 30 nm and a specific surface area of 43 m 2 /g) and the 3% N-containing CNFs from the pre-oxidized CNFs by thermal treatment (10 g) with NH3 at 600 °C for 4 h, as reported in [32]. TiO2 (P25) was purchased from Degussa (SA = 50 m 2 /g).…”

Preparation of amino functionalized imidazolium-modified silicas by different coupling agents for removal of 2,4-dinitrophenol from aqueous solutions

“…Amino group is easily protonated under acidic conditions and also contributes to the basic properties, so the surface basicity of imidazole-modified silicas will be further enhanced when amino group is grafted onto imidazole through alkyl chain. For example, amination of activated carbon showed an outstanding enhancement of phenol adsorption (Arrigo et al 2010;Yang et al 2014). Generally, ionic liquidmodified silicas are composed of cations, anions and coupling agents between silica and imidazole.…”