Jianhao Qiu

Safe and facile hydrogenation of commercial Degussa P25 at room temperature with enhanced photocatalytic activity

In this paper, we developed a new safe and facile route to prepare black titania at room temperature for visible light photocatalysis. The commercial Degussa P25 was used as the starting material, and it was hydrogenated at 35 bar hydrogen and room temperature for up to 20 days. The resulting hydrogenated P25 was characterized by XRD, FT-IR, Raman, UV-Vis, TEM and photocatalysis tests under visible light in methanol solution. It was found that P25 powders under hydrogen treated for more than 15 days have a dark appearance, a crystalline-disordered core–shell structure, unique phase structure and good photocatalytic performance. The H2 evolution rates are 3.14, 3.56 and 3.94 mmol g−1 h−1 in 20% methanol solution for hydrogen treated P25 at 15, 17 and 20 days, respectively, which were largely higher than that with hydrogen treatment time less than 11 days. This work will provide a practical, green and facile method for the large scale synthesis of black titania at room temperature.

Acid-promoted synthesis of UiO-66 for highly selective adsorption of anionic dyes: Adsorption performance and mechanisms

UiO-66 was modulated by addition of acetic acid or HCl in the precursor solution. The resulting acetic acid-promoted UiO-66has more regular octahedral structures and high surface areas of 892-1090m2/g. Anionic dyes (methyl orange (MO) and Congo red (CR)) and cationic dyes (methylene blue (MB) and rhodamine B (RhB)) were examined for the selective dye adsorption on various UiO-66. The acid-promoted UiO-66 exhibits an excellent selective adsorption to anionic dyes, where the adsorption capacities of MO and MB are 84.8 and 13.2mg/g, respectively. However, UiO-66 prepared without acid shows similar adsorption to both anionic dye MO (70.4mg/g) and cationic dye MB (67.5mg/g). Mixed dyes (MO/MB and MO/RhB) adsorption on acid-promoted UiO-66 further proves the selective adsorption to anionic dyes. The adsorption mechanism was studied by testing the Zeta potential of acid-promoted UiO-66, and more positive Zeta potential (hydrogen ions) of UiO-66 is beneficial to the anionic dye adsorption.

Facile stir-dried preparation of g-C3N4/TiO2 homogeneous composites with enhanced photocatalytic activity

g-C3N4/TiO2 composites with homogeneous well-combined structures were prepared by a simple stir-dried method, using dicyandiamide (DICY) and tetrabutyl orthotitanate (TBOT) as the precursors, followed by high-temperature calcination. Various characterization techniques including XRD, FTIR, nitrogen adsorption–desorption, SEM and XPS confirm the formation of an interconnected structure between g-C3N4 and TiO2 in the composites. g-C3N4/TiO2 composites exhibit much higher photocatalytic activity than that of pure g-C3N4 and TiO2 in the degradation of methylene blue under visible light. In particular, the CT-5 composite prepared with DICY/TBOT at a mass ratio of 5 : 1, exhibited a photodegradation activity that is about 3.8 times that of TiO2 and 2.9 times that of pure g-C3N4. The homogeneous g-C3N4/TiO2 composite CT-5 can be repetitively used without significant loss of activity. The strong synergistic effect between g-C3N4 and TiO2 achieved by this preparation method greatly improves the separation efficiency of photo-generated electrons and holes, thus offering enhanced photocatalytic performances.

Facile synthesis of TaOxNy photocatalysts with enhanced visible photocatalytic activity

N-doped TaOxNy is prepared using ethylenediamine as the nitrogen source by a sol–gel method. The obtained samples are subsequently calcined at 500–900 °C. XRD analysis and XPS survey indicate the presence of immature TaO2 (Ta4+) in the N-doped TaOxNy sample sintered at 550 °C (TaOxNy-550), and the UV results show TaOxNy-550 has a rather strong absorption in the visible light region. The photocatalytic activities of TaOxNy are evaluated in hydrogen generation by water splitting and photodegradation of methyl orange. The N-doped TaOxNy sample sintered at 550 °C shows the highest H2 generation rate of 3.12 mmol g−1 h−1, and only 3.1% methyl orange is left after 90 min irradiation. Such photocatalytic activities are comparable to the conventional nitrogen-doped titania.

Constructing Cd 0.5 Zn 0.5 S@ZIF-8 nanocomposites through self-assembly strategy to enhance Cr(VI) photocatalytic reduction

A novel and highly efficient photocatalyst of Cd0.5Zn0.5S@ZIF-8 nanocomposite has been developed by a facile self-assembly strategy. This is the first report on the application of CdxZn1-xS and metal-organic framework (MOF) nanocomposite as photocatalysts for the reduction of Cr(VI). The resulting Cd0.5Zn0.5S@ZIF-8 exhibited higher photocatalytic activity than that of pristine Cd0.5Zn0.5S and ZIF-8. Particularly, the CZS@Z60 composite with 60 wt% of ZIF-8 exhibited a photocatalytic activity that is about 1.6 times as high as that of Cd0.5Zn0.5S. The dominant reason for the improved photocatalytic reduction potential is proved to be the newly-formed interfacial SZn bonds that firmly connect Cd0.5Zn0.5S and ZIF-8 and substantially improve the separation efficiency of photo-excited electrons and holes. The newly-formed chemical bonds are confirmed by XPS analyses, and the prolonged lifetime of photo-excited electrons is evidenced by the electrochemical measurement of photocurrent, which shows that the photocurrent on Cd0.5Zn0.5S@ZIF-8 is much higher than that of Cd0.5Zn0.5S and ZIF-8. This study clearly demonstrates that the MOF-based composite nanomaterials hold great promises for applications in the field of environmental remediation and for design of novel photocatalytic materials.