Hydrophobic Carbon-Doped TiO₂/MCF‑F Composite as a High Performance Photocatalyst

A novel hydrophobic photocatalyst carbon-doped TiO₂/MCF-F was prepared by using silica mesoporous cellular foam (MCF) as host material, glucose as carbon source, and NH₄F as hydrophobic modifying agent. It was confirmed that titania nanoparticles were loaded in pore of MCF by XRD, N₂ sorption isotherms, and TEM. The loaded titania nanoparticles exhibited higher photocatalytic performance. UV–vis absorption spectra and XPS suggested carbon atoms were doped in the lattice of titania by replacing titanium atoms and narrowed the band gap so that visible light absorption and photocatalytic activity of the photocatalyst were highly promoted. On the other hand, water contact angle measurement and XPS proved that the photocatalyst was endowed with hydrophobic property, which was caused by Si–F bonds. Carbon-doped TiO₂/MCF-F photocatalyst showed good adsorptive ability and photocatalytic activity in the photodegradation test of methyl orange under visible light

Mesoporous TiO₂ Nanocrystals Grown in Situ on Graphene Aerogels for High Photocatalysis and Lithium-Ion Batteries

TiO₂/graphene composites have been well studied as a solar light photocatalysts and electrode materials for lithium-ion batteries (LIBs). Recent reports have shown that ultralight 3D-graphene aerogels (GAs) can better adsorb organic pollutants and can provide multidimensional electron transport pathways, implying a significant potential application for photocatalysis and LIBs. Here, we report a simple one-step hydrothermal method toward in situ growth of ultradispersed mesoporous TiO₂ nanocrystals with (001) facets on GAs. This method uses glucose as the dispersant and linker owing to its hierarchically porous structure and a high surface area. The TiO₂/GAs reported here exhibit a highly recyclable photocatalytic activity for methyl orange pollutant and a high specific capacity in LIBs. The strong interaction between TiO₂ and GAs, the facet characteristics, the high electrical conductivity, and the three-dimensional hierarchically porous structure of these composites results in highly active photocatalysis, a high rate capability, and stable cycling

Economic Hydrophobicity Triggering of CO₂ Photoreduction for Selective CH₄ Generation on Noble-Metal-Free TiO₂–SiO₂

On the basis of the fact that the competitive adsorption between CO₂ and H₂O on the catalyst plays an important role in the CO₂ photoreduction process, here we develop an economic NH₄F-induced hydrophobic modification strategy to enhance the CO₂ competitive adsorption on the mesoporous TiO₂–SiO₂ composite surface via a simple solvothermal method. After the hydrophobic modification, the CO₂ photoreduction for the selective generation of CH₄ over the noble-metal-free TiO₂–SiO₂ composite can be greatly enhanced (2.42 vs 0.10 μmol/g in 4h). The enhanced CO₂ photoreduction efficiency is assigned to the rational hydrophobic modification on TiO₂–SiO₂ surface by replacing Si–OH to hydrophobic Si–F bonds, which will improve the CO₂ competitive adsorption and trigger the eight-electron CO₂ photoreduction on the reaction kinetics

Rational Design of a Unique Ternary Structure for Highly Photocatalytic Nitrobenzene Reduction

The rational design and controllable synthesis of TiO₂ and noble metal composite photocatalysts represent an unprecedented challenge for developing the solar-driven reduction of nitrobenzene (NB) to aminobenzene (AB), owing to the recombination over the interface between the noble metals and TiO₂, which is harmful to the conversion efficiency of NB to AB. Here, we design a unique ternary structure (the high separation of TiO₂ and Pt nanoparticles on the surface of reduced graphene oxide (RGO)) through the sol–gel and microwave-assisted strategies. The substrate of RGO can be used as an “electric wire” to effectively transfer the photogenerated electrons from the isolated TiO₂ nanocrystals to the isolated Pt nanoparticles, which greatly decreases the interface recombination between TiO₂ and Pt and further improves the conversion efficiency of NB to AB under the solar light irradiation. We anticipate our research provides a new way to overcome the interface recombination on the binary photocatalysts in the photocatalytic reaction

Zn-Assisted TiO_2–<i>x</i> Photocatalyst with Efficient Charge Separation for Enhanced Photocatalytic Activities

A new Zn-assisted method has been employed to synthesize reduced TiO₂(TiO_2–<i>x</i>) photocatalyst via a one-step hydrothermal process. In order to prevent the oxidation of TiO_2–<i>x</i> in air, hydrofluoric acid is introduced in the preparative process for the stabilization of the Ti³⁺ and oxygen vacancies, as confirmed by low-temperature electron paramagnetic resonance. The obtained reduced TiO₂ presents a wide-spectrum solar light absorption, including the near-infrared region. In addition, {110}–{111} and {101}–(001) dual-facet exposures are generated by Cl- and F-based surface-terminated reagents, respectively. The generated {001} and {101} facets on reduced TiO₂ samples act as hole and electron collectors, respectively, which contributes to the charge separation of the catalyst. Finally, the synergistic effect between Ti³⁺ doping and dual-facet exposure results in the high photocatalytic performance for degradation of Rhodamine B and formic acid

Modulation of the Reduction Potential of TiO_2–<i>x</i> by Fluorination for Efficient and Selective CH₄ Generation from CO₂ Photoreduction

Photocatalytic reduction of CO₂ holds great promises for addressing both the environmental and energy issues that are facing the modern society. The major challenge of CO₂ photoreduction into fuels such as methane or methanol is the low yield and poor selectivity. Here, we report an effective strategy to enhance the reduction potential of photoexcited electrons by fluorination of mesoporous single crystals of reduced TiO_2–<i>x</i>. Density functional theory calculations and photoelectricity tests indicate that the Ti³⁺ impurity level is upswept by fluorination, owing to the built-in electric field constructed by the substitutional F that replaces surface oxygen vacancies, which leads to the enhanced reduction potential of photoexcited electrons. As a result, the fluorination of the reduced TiO_2–<i>x</i> dramatically increases the CH₄ production yield by 13 times from 0.125 to 1.63 μmol/g·h under solar light illumination with the CH₄ selectivity being improved from 25.7% to 85.8%. Our finding provides a metal-free strategy for the selective CH₄ generation from CO₂ photoreduction