Bi5+-self-doped Bi4V2O11 (Bi5+-BVO) nanotubes with p–n homojunctions are fabricated via an oxygen-induced strategy. Calcinating the as-spun fibers with abundant oxygen plays a pivotal role in achieving Bi5+ self-doping. Density functional theory calculations and experimental results indicate that Bi5+ self-doping can narrow the band gap of Bi4V2O11, which contributes to enhancing light harvesting. Moreover, Bi5+ self-doping endows Bi4V2O11 with n- and p-type semiconductor characteristics simultaneously, resulting in the construction of p–n homojunctions for retarding rapid electron–hole recombination. Benefiting from these favorable properties, Bi5+-BVO exhibits a superior photocatalytic performance in contrast to that of pristine Bi4V2O11. Furthermore, this is the first report describing the achievement of p–n homojunctions through self-doping, which gives full play to the advantages of self-doping.Keywords: Bi4V2O11; density functional theory; photocatalysis; p−n homojunction; self-doping;

Two-dimensional polymers are of great interest for many potential applications in nanotechnology. The preparation of crystalline 2D polymers with a tunable band gap is critical for their applications in nano-electronics and optoelectronics. In this work, we try to tune the band gap of 2D imine polymers by expanding the conjugation of the backbone of aromatic diamines both laterally and longitudinally. STM characterization reveals that the regularity of the 2D polymers can be affected by the existence of lateral bulky groups. Density functional theory (DFT) simulations discovered a significant narrowing of the band gap of imine 2D polymers upon the expansion of the conjugation of the monomer backbone, which has been confirmed experimentally by UV absorption measurements. Monte Carlo simulations help us to gain further insight into the controlling factors of the formation of regular 2D polymers, which demonstrated that based on the all rigid assumption, the coexistence of different conformations of the imine moiety has a significant effect on the regularity of the imine 2D polymers.

A two-dimensional covalent organic framework (2D COF), synthesized on a highly oriented pyrolytic graphite (HOPG) surface with benzene-1,3,5-tricarbaldehyde and p-phenylenediamine as the precursors, is used as a host to accommodate three guest molecules, coronene, copper phthalocyanine (CuPc), and fluorine-substituted copper phthalocyanine (F16CuPc). The host–guest interaction and dynamic behavior were investigated by scanning tunneling microscopy and density functional theory.

We have designed and synthesized two porphyrin containing two-dimensional (2D) polymers based on the imine linkage. Both the 2D polymers are revealed to be 2D organic semiconductors with band gaps of around 1 eV. STM characterization reveals that the rigidity and affinity of building blocks to the surface has essential effects on the topology of the 2D polymers.

Single-crystalline anatase TiO2 nanobelts with a dominant surface of the {101} facet were hydrogenated and used as substrates of platinum for methanol oxidation reaction (MOR). The hydrogenated TiO2 anatase{101} supporting Pt exhibits a 228% increase of current density for methanol oxidation compared with the same system without hydrogenation under dark conditions. The synergetic interactions of hydrogenated anatase{101} with the Pt cluster were investigated through first principles calculations, and found that the hydrogenation shifts the conduction band minimum to the Fermi level of pristine TiO2, and reduces the activation barrier for methanol dissociation considerably. Thus, this work provides an experimental and theoretical basis for developing non-carbon substrates with high electro-catalytic activity toward MOR.

•Relationship between the electronic structures and UV spectra of C96 isomers.•The NLO responses of C96 isomers under an external field.•Show averaged NLO responses of the C96 isomers at different temperatures.Electronic spectra, and the nonlinear optical (NLO) properties of five isomers of C96 were investigated using density functional theory and semi-empirical methods. The simulated electronic spectra of C2:181, C1:144, C1:145, and C2:176 have strong absorptions above 500 nm. The electronic spectra of C1:144, C1:145, and C2:176 are similar. The third-order NLO properties of the isomers were analyzed under an external field. Small structural differences between C1:144 and C1:145 result in NLO responses that occur at different external fields. Entropy effects on the NLO properties are significant. The NLO responses of the five most stable isomers differ in the concentration averaged sample.

The lowest-lying 10 isomers of C106 satisfying the isolated-pentagon rule (IPR) were predicted from 1233 IPR isomers with semiempirical and density functional theory based methods. The structures, stabilities, IR and UV spectroscopic, and the third-order nonlinear optical (NLO) properties of those low-lying isomers were explored in detail. Cs:331, C2:1194, and C1:534 are the three lowest-energy isomers with almost identical energies and could be observed in experiment. When the entropy effects in the isomeric fullerene system are taken into account, isomer C2:1194 prevails up to 3000 °C. In the high temperature region, the concentrations of those ten low-lying isomers are very similar, indicating that the isomers at high temperatures will be hard to isolate. The third-order NLO properties under external fields (0.0–3.0 eV) of the five lowest-lying isomers were analyzed, and the average NLO properties of those isomers were predicted at room temperature for experimental exploration.

Density functional theory based calculations have been performed to investigate decomposition of HCOOH on a Pd7 cluster in vacuum and solution. The adsorption of HCOOH on Pd7 cluster occurs on a layer-by-layer quasi-planar conformation of Pd7 with 4 atoms on top and 3 atoms below. Possible reaction pathways for the decomposition of HCOOH adsorbed on Pd7 cluster in vacuum and solution are located and compared in terms of the reaction enengies and barriers. Formic acid prefers to decompose through dehydrogenation rather than dehydrate under the significant effect of solvent. The toxic species, CO generated on Pt surface, could not possibly appear in the catalytic decomposition of formic acid on Pd7 cluster due to high reaction barrier, thus no poisoning of catalyst would occur on Pd surface. The Pd7 cluster model rationalizes experimental observation, and the predictions are in good agreement with the ones based on the surface model.

A two-dimensional covalent organic framework (2D COF), synthesized on a highly oriented pyrolytic graphite (HOPG) surface with benzene-1,3,5-tricarbaldehyde and p-phenylenediamine as the precursors, is used as a host to accommodate three guest molecules, coronene, copper phthalocyanine (CuPc), and fluorine-substituted copper phthalocyanine (F16CuPc). The host–guest interaction and dynamic behavior were investigated by scanning tunneling microscopy and density functional theory.

We have designed and synthesized two porphyrin containing two-dimensional (2D) polymers based on the imine linkage. Both the 2D polymers are revealed to be 2D organic semiconductors with band gaps of around 1 eV. STM characterization reveals that the rigidity and affinity of building blocks to the surface has essential effects on the topology of the 2D polymers.

Single-crystalline anatase TiO2 nanobelts with a dominant surface of the {101} facet were hydrogenated and used as substrates of platinum for methanol oxidation reaction (MOR). The hydrogenated TiO2 anatase{101} supporting Pt exhibits a 228% increase of current density for methanol oxidation compared with the same system without hydrogenation under dark conditions. The synergetic interactions of hydrogenated anatase{101} with the Pt cluster were investigated through first principles calculations, and found that the hydrogenation shifts the conduction band minimum to the Fermi level of pristine TiO2, and reduces the activation barrier for methanol dissociation considerably. Thus, this work provides an experimental and theoretical basis for developing non-carbon substrates with high electro-catalytic activity toward MOR.