TiO2 Band Restructuring by B and P Dopants

Surface-Enriched Boron-Doped TiO2 Nanoparticles as Photocatalysts for Propene Oxidation

A series of nanostructured boron-TiO₂ photocatalysts (B-X-TiO₂-T) were prepared by sol-gel synthesis using titanium tetraisopropoxide and boric acid. The effects of the synthesis variables, boric acid amount (X) and crystallization temperature (T), on structural and electronic properties and on the photocatalytic performance for propene oxidation, are studied. This reaction accounts for the remediation of pollution caused by volatile organic compounds, and it is carried out at low concentrations, a case in which efficient removal techniques are difficult and costly to implement. The presence of boric acid during the TiO₂ synthesis hinders the development of rutile without affecting the textural properties. X-ray photoelectron spectroscopy analysis reveals the interstitial incorporation of boron into the surface lattice of the TiO₂ nanostructure, while segregation of B₂O₃ occurs in samples with high boron loading, also confirmed by X-ray diffraction. The best-performing photocatalysts are those with the lowest boron loading. Their high activity, outperforming the equivalent sample without boron, can be attributed to a high anatase and surface hydroxyl group content and efficient photo-charge separation (photoelectrochemical characterization, PEC), which can explain the suppression of visible photoluminescence (PL). Crystallization at 450 °C renders the most active sample, likely due to the development of a pure anatase structure with a large surface boron enrichment. A shift in the wavelength-dependent activity profile (PEC data) and the lowest electron-hole recombination rate (PL data) are also observed for this sample.

Theoretical assessment of wettability on silane coatings: from hydrophilic to hydrophobic

The potential distribution and work function of a graphene surface modified by various types of silanes are investigated by first principles quantum mechanical calculations to establish its surface hydrophobicity hierarchy. It is found that the work function relies on the electronegativity of atoms on silane. The localization feature of interaction between silane and the graphene surface is demonstrated by the electron density difference. The work function is demonstrated to be a critical quantity in understanding the surface polarizability and thereby the surface wetting properties. By performing contact angle measurements experimentally using water as the probe fluid, surfaces grafted with different silanes show hydrophobicity variation that is found to follow the reverse trend to that of the proposed surface polarizability obtained through the work function calculation. The work function-dependent contact angle can be fitted with a linear equation.