Chencheng Dong

Modulation of the Reduction Potential of TiO2–x 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 TiO2- x. 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 TiO2- x 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.

Sulfur nanoparticles in situ growth on TiO2 mesoporous single crystals with enhanced solar light photocatalytic performance

We employed a facile method to realize sulfur nanoparticles in situ growth on TiO2 mesoporous single crystals (MSCs). The prepared photocatalysts were characterized by XRD, Raman, UV-vis absorption spectra, XPS, TEM, FESEM, TG/DTA and photoluminescence (PL) emission spectra. The average sulfur particle size is around 8 nm, and we utilized various volumes of ammonium polysulfide ((NH4)2Sx) to tailor the loading of sulfur nanoparticles. When the loading content is 27.2 wt%, they exhibit the optimal photoactivity in degrading acid orange 7 (AO7). In comparison with the pure MSCs (P-TiO2 MSCs), the removal rate of 30S-TiO2 MSCs can be enhanced about 90% under solar light irradiation, and after 5 cycles it retains a high photocatalytic performance.

In situ strategy to prepare PDPB/SnO2 p–n heterojunction with a high photocatalytic activity

As a novel material for water depollution, conjugated polydiphenylbutadiyne (PDPB) nanofibers have received attention due to their visible light responsive photocatalytic activity. In this study, we successfully prepared a PDPB/SnO2 p–n heterojunction by an in situ growth route. The XPS characterization indicates the generation of Sn–C bonds between SnO2 and PDPB, which would decrease the bandgap of SnO2 and promote the transference efficiency of electrons and holes between these two components. The PDPB could act as the sensitizer to enlarge the solar light absorption region of the heterojunction. The SnO2 provides a stable mesoporous structure and enhanced hydrophilic properties. The solar-driven photodegradation rate of Rhodamine B over the PDPB/SnO2 (ratio is 2 : 1) is 4 times higher than that of the pure SnO2 and 2 times higher than that of the pure PDPB nanofibers. Our strategy gives a facile strategy for the preparation of an organic–inorganic hybrid heterojunction with high solar light activity.

Development of titanium oxide-based mesoporous materials in photocatalysis

With the prevalence of green chemistry and the concept of a harmonious society, humans have much greater environmental awareness than ever before. Mesoporous TiO2 and its corresponding photocatalysts can assist the search for a better and more ideal life. In this review, we first briefly introduce the development of various mesoporous materials, after which we discuss the preparation and application of mesoporous TiO2 materials in photocatalysis. When titanium oxide-based mesoporous materials are applied in photocatalysis, they exhibit excellent performance and many advantages in pollutant decomposition and H2 evolution. In addition to the traditional TiO2-based mesoporous materials, novel materials such as Ti-metal organic frameworks are reviewed, as their application in H2 evolution has garnered increasing research interest in recent years. It is evident from literature surveys that these TiO2-based mesoporous photocatalysts have significant potential for use in environmental and energy applications.

Enhancement of H2O2 Decomposition by the Co-catalytic Effect of WS2 on the Fenton Reaction for the Synchronous Reduction of Cr(VI) and Remediation of Phenol

The greatest problem in the Fe(II)/H2O2 Fenton reaction is the low production of ·OH owing to the inefficient Fe(III)/Fe(II) cycle and the low decomposition efficiency of H2O2 (<30%). Herein, we report a new discovery regarding the significant co-catalytic effect of WS2 on the decomposition of H2O2 in a photoassisted Fe(II)/H2O2 Fenton system. With the help of WS2 co-catalytic effect, the H2O2 decomposition efficiency can be increased from 22.9% to 60.1%, such that minimal concentrations of H2O2 (0.4 mmol/L) and Fe2+ (0.14 mmol/L) are necessary for the standard Fenton reaction. Interestingly, the co-catalytic Fenton strategy can be applied to the simultaneous oxidation of phenol (10 mg/L) and reduction of Cr(VI) (40 mg/L), and the corresponding degradation and reduction rates can reach up to 80.9% and 90.9%, respectively, which are much higher than the conventional Fenton reaction (52.0% and 31.0%). We found that the expose reductive W4+ active sites on the surface of WS2 can greatly accelerate the rate-limiting step of Fe3+/Fe2+ conversion, which plays the key role in the decomposition of H2O2 and the reduction of Cr(VI). Our discovery represents a breakthrough in the field of inorganic catalyzing AOPs and greatly advances the practical utility of this method for environmental applications.