Saisai Yuan

Synthesis high specific surface area nanotube g-C3N4 with two-step condensation treatment of melamine to enhance photocatalysis properties

High specific surface area nanotube g-C3N4 was fabricated by a simple two-step condensation method. Photocatalytic activity was evaluated by decomposition of Rhodamine B (Rh B) under visible light. Nanotube g-C3N4 showed 12 times higher photocatalytic activity than bulk g-C3N4. The improvement of photocatalytic activity was mainly due to the higher surface area, the unique morphology and the number of defects.

Porous cerium dioxide hollow spheres and their photocatalytic performance

Uniform-sized and monodiperse cerium dioxide porous hollow spheres (CeO2-PH) based on the Ostwald ripening process were fabricated by a simple solvothermal method in the absence of any templates. The structure and morphology of CeO2-PH and CeO2-NP (cerium dioxide nanoparticles) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Brunauer–Emmett–Teller (BET) surface area analysis. The average diameter of face-centered cubic (fcc) phase CeO2-PH was ca. 160 nm with a high specific surface area, and it is composed of small crystal grain particles (ca. 10 nm). Furthermore, CeO2-PH has high activity for the evaluation of acetaldehyde decomposition. Optical, defect, and chemical state properties were characterized by Raman spectra, ultraviolet-visible absorption spectroscopy (UV-vis), and X-ray photoelectron spectroscopy (XPS). The presence of Ce3+ ions narrowed the band gap of CeO2-PH, resulting in the high light harvesting. The large amount of oxygen vacancy defects provided many activity sites on CeO2-PH in the photocatalytic process. The formation scheme and photocatalyic mechanism will be discussed in this paper.

A new precursor to synthesize g-C3N4 with superior visible light absorption for photocatalytic application

Graphitic carbon nitride (g-C3N4) was synthesized with a new precursor (thiourea oxide) by a simple one-pot calcination method. Sulphur–oxygen co-doping could modulate the band structure of pristine g-C3N4, resulting in an absorption edge of up to 600 nm, which is well consistent with DFT calculation. Thus, its photocatalytic properties were enhanced.

Effects of the Atmosphere in a Hydrothermal Process on the Morphology and Photocatalytic Activity of Cerium Oxide

The hydrothermal method is widely applied in nanomaterials synthesis, and most of the influencing factors have already been taken into account. However, the effect of atmosphere in solution on the performance of nanomaterials has been underestimated for a long time. In this article, reaction solvents were saturated with three classical gases (argon, oxygen, and carbon dioxide), and then heated at 180 °C for 24 h to obtain the cerium dioxide (CeO2) nanoparticles. The properties of the three types of CeO2 are significantly different from that of the normal CeO2 (without gas saturation). The morphologies of the prepared CeO2 particles are different, even appear the hollow structure in CeO2−CO2 (synthesized in CO2 saturated condition). The more absorbing and meaningful thing is that the photocatalytic activity of CeO2−CO2 has been greatly improved. The concordance of the CO2 atmosphere (acid gas) and CeO2 (owning substantial content of basic sites) is the key point for the excellent photocatalytic performance.

Development of the Visible‐Light Response of CeO2−x with a high Ce3+ Content and Its Photocatalytic Properties

Photocatalysts that are responsive to visible light are necessary to utilize solar energy. We prepared reduced CeO2−x with absorption in the visible region by a simple solvothermal method. A new absorption band appearing at λ≈500 nm (surface plasmon resonance) could be ascribed to the high content of Ce3+. To elucidate the relationship between Ce3+ and activity, the decomposition of isopropyl alcohol (IPA) to generate acetone was performed under visible‐light irradiation. CeO2−x showed activity that was superior to that of pure CeO2. Ce3+ induced oxygen vacancies in the lattice of CeO2−x, and this resulted in an improvement in the activity. In addition, the introduction of Ce3+ resulted in an improvement in the absorption of CeO2−x in the visible‐light region. Also, the appearance of small tentacles (Confeito‐like) on the surface of CeO2−x not only provided more active sites but also prevented aggregation. Owing to its visible‐light responsiveness and unique morphology, the performance of this material was significantly improved relative to that of pure CeO2.