Characterization by SEM, TEM and Quantum-Chemical Simulations of the Spherical Carbon with Nitrogen (SCN) Active Carbon Produced by Thermal Decomposition of Poly(vinylpyridine-divinylbenzene) Copolymer

Amorphous Spherical Carbon with Nitrogen (SCN) active carbon has been prepared by carbonization of poly(vinylpyridine-divinylbenzene) (PVPDVB) copolymer. The PVPDVB dehydrogenation copolymer has been quantum chemically (QC) simulated using cluster and periodic models. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) studies of the resulting product have conformed the QC computation results. Great structural similarity is found both at the nano- and micro-levels between the N-doped SCN carbon and its pure carbonic SKS analog

Quantum Chemical Simulation of Phenol-Formaldehyde Resin Carbonization in the Presence of Phosphoric Acid: Computational Evidence of Michaelis–Arbuzov-Type Reaction

Quantum-chemical semiempirical simulation of phenol-formaldehyde resin carbonization was performed by PM6 method, resulting in atomic level models of neat and P-doped disordered carbon structures. Mechanisms of curved-plane carbon fragments formation from postpolymeric chains is discussed, supported by change in statistic characteristics of the clusters. Transformation of phosphoric esters to phosphonates by Michaelis–Arbuzov-type reaction is described

Quantum Chemical Simulation of Phenol-Formaldehyde Resin Carbonization in the Presence of Phosphoric Acid: Computational Evidence of Michaelis–Arbuzov-Type Reaction

Quantum-chemical semiempirical simulation of phenol-formaldehyde resin carbonization was performed by PM6 method, resulting in atomic level models of neat and P-doped disordered carbon structures. Mechanisms of curved-plane carbon fragments formation from postpolymeric chains is discussed, supported by change in statistic characteristics of the clusters. Transformation of phosphoric esters to phosphonates by Michaelis–Arbuzov-type reaction is described

Quantum Chemical Simulation of Phenol-Formaldehyde Resin Carbonization in the Presence of Phosphoric Acid: Computational Evidence of Michaelis–Arbuzov-Type Reaction

Quantum-chemical semiempirical simulation of phenol-formaldehyde resin carbonization was performed by PM6 method, resulting in atomic level models of neat and P-doped disordered carbon structures. Mechanisms of curved-plane carbon fragments formation from postpolymeric chains is discussed, supported by change in statistic characteristics of the clusters. Transformation of phosphoric esters to phosphonates by Michaelis–Arbuzov-type reaction is described

Density Functional Theory versus Complete Active Space Self-Consistent Field Investigation of the Half-Metallic Character of Graphite-Like and Amorphous Carbon Nanoparticles

Model carbon nanoparticles representative of the graphite-like and amorphous domains of active carbon are investigated with density functional theory (DFT) and complete active space self-consistent field (CASSCF) methods. Cyclic carbon clusters containing conjugated carbene groups are found to undergo Jahn–Teller distortion. More importantly, the half-metallicity, that is, the equal or similar stability of various spin states, previously suggested by DFT calculations for both types of nanosized clusters is confirmed by CASSCF calculations. Furthermore, the model carbon clusters are found to possess a multiconfigurational electronic structure dominated by high-spin configurations. When compared to CASSCF results, the single-reference DFT predicts proper electronic structures, characterized by antiferromagnetically coupled electron pairs, at the expense of spin contamination as a reflection of the multiconfigurational character. In fact, spin contamination, which is normally viewed as an error, does not corrupt the energetics of the half-metallic systems and therefore does not preclude the applicability of DFT to such systems

Visible-light photocurrent response of TiO2-polyheptazine hybrids: evidence for interfacial charge-transfer absorption

We investigated photoelectrodes based on TiO2-polyheptazine hybrid materials. Since both TiO2 and polyheptazine are extremely chemically stable, these materials are highly promising candidates for fabrication of photoanodes for water photooxidation. The properties of the hybrids were experimentally determined by a careful analysis of optical absorption spectra, luminescence properties and photoelectrochemical measurements, and corroborated by quantum chemical calculations. We provide for the first time clear experimental evidence for the formation of an interfacial charge-transfer complex between polyheptazine (donor) and TiO2 (acceptor), which is responsible for a significant red shift of absorption and photocurrent response of the hybrid as compared to both of the single components. The direct optical charge transfer from the HOMO of polyheptazine to the conduction band edge of TiO2 gives rise to an absorption band centered at 2.3 eV (540 nm). The estimated potential of photogenerated holes (+1.7 V vs. NHE, pH 7) allows for photooxidation of water (+0.82 V vs. NHE, pH 7) as evidenced by visible light-driven (lambda > 420 nm) evolution of dioxygen on hybrid electrodes modified with IrO2 nanoparticles as a co-catalyst. The quantum-chemical simulations demonstrate that the TiO2-polyheptazine interface is a complex and flexible system energetically favorable for proton-transfer processes required for water oxidation. Apart from water splitting, this type of hybrid materials may also find further applications in a broader research area of solar energy conversion and photo-responsive devices