Photocatalytic Degradation of Crystal Violet on Cu, Zn Doped BiVO4 Particles.

Fabrication of codoped photocatalysts is a developing area of research. Herein, we explore the visible light photocatalytic properties of Cu, Zn codoped BiVO4 particles. Doping lower valent cations (Cu and Zn) makes the BiVO4 surface more acidic and enables us to target the basic crystal violet (CV) dye. The adopted hydrothermal protocol of synthesis results in the formation of Cu-Zn codoped monoclinic BiVO4 particles. Undoped monoclinic BiVO4, prepared by the same protocol, showed significant formation of oxygen vacancies. XPS analyses confirm the coexistence of Cu2+/Cu+ and Zn2+ dopants. Increased dopant percentage reduced oxygen vacancies. XRD indicates that Cu2+/Cu+ or Zn2+ dopants generally substitute Bi3+ in BiVO4. All photocatalysis activities for CV degradation are reported under near-neutral pH conditions. A typical codoped BiVO4 photocatalyst with 1% Zn and 2% Cu demonstrated the best CV degradation photocatalytic activity. The activity of this Zn, Cu codoped photocatalyst is better than that of pure, Zn-doped, and Cu-doped BiVO4 samples. Active species trapping experiments indicated the possible photocatalysis mechanism. The photocatalysts exhibited appropriate recyclability and photostability.

Magnetic Ni@C nanoadsorbents for methyl orange removal from water.

In this study, Ni@C nanoparticles were produced and used as an adsorbent for removing methyl orange (MO) from an aqueous solution. The sol-gel method was utilized for the preparation of the particles. The X-ray diffraction pattern and transmission electron microscopy (TEM) were utilized to determine the phase, morphology, and size. The electron micrograph indicated the coating of carbon over Ni having size between 43 and 94 nm, and the Raman spectrum supported it. Among three, the maximum specific magnetization of the Ni@C nanocomposite was 55.78 emu/g for the N7 sample. From the BET approach, specific surface areas of 2.29 × 105, 3.66 × 105, and 5.48 × 105 cm2/g as well as average pore size of 49.30, 37.25, and 35.27 nm were observed for N5, N6, and N7, respectively. The Ni@C nanoparticles were magnetically separable and exhibited rapid adsorption of MO of different concentrations from their aqueous solutions. The N7 adsorbent displayed the highest MO adsorption capacity (~ 32 mg·g-1) along with maintaining an adsorption capacity of 81% even after 5 cycles. Adsorption isotherm and kinetic analysis gave critical inputs toward the possible adsorption mechanism.

The bandgap of sulfur-doped Ag2O nanoparticles.

A narrow band gap restricts photocatalytic applications of Ag2O nanoparticles, but appropriate doping can favorably modify this aspect. Given this, density functional theory (DFT) calculations were conducted, revealing that substitutional sulfur doping of Ag2O could increase its bandgap and stabilize oxygen vacancies. A hydrothermal precipitation protocol was employed to prepare sulfur-doped (S-doped) Ag2O nanoparticles. The band gap of the prepared nanoparticles increased to 1.89 eV with 1.25-mole percent S-doping. XPS analysis of the samples also revealed that S-doping increased oxygen vacancies in the prepared Ag2O nanoparticles. Furthermore, S-doping caused a major shift in the valence band position to a negative value. These doped Ag2O nanoparticles showed an enhanced visible-light photocatalytic activity towards rhodamine B (RhB) degradation.

Cd-doped Ag2O/BiVO4 visible light Z-scheme photocatalyst for efficient ciprofloxacin degradation.

Foreign element doping can produce new photocatalysts with different band edge positions and adsorption properties. A composite of such a doped semiconductor with another component should enhance its photocatalytic properties towards a target substrate. The present investigation used a simple hydrothermal protocol to prepare Cd-doped Ag2O nanoparticles. The Cd-doping of Ag2O nanoparticles changed its valence band maximum position from 0.8 eV (for undoped Ag2O nanoparticles) to 2.67 eV with a slight narrowing of the Ag2O bandgap. A combination of DFT calculation and XRD results showed that the dopant Cd substituted Ag in the Ag2O lattice. The doped material is an effective photocatalyst for ciprofloxacin degradation but with poor recyclability. The joining of a BiVO4 part to the Cd-doped Ag2O nanostructures gave a composite with improved photocatalytic activity and recyclability towards ciprofloxacin degradation. DFT calculations showed that BiVO4 has a higher oxygen affinity than Cd-doped Ag2O. The XPS characterization of the composite and appropriate active species scavenger experiments demonstrated a Z-scheme mechanism. Superoxide radicals play a critical role in CIP degradation.

AgI/CuWO4 Z-scheme photocatalyst for the degradation of organic pollutants: Experimental and molecular dynamics studies.

While the knowledge of the adsorption properties of components of a composite heterogeneous photocatalyst is critical to its applicability to a particular reaction, there has been little research in this direction. The present research is on the development of AgI/CuWO4 nanocomposites that photocatalytically degraded ciprofloxacin and rhodamine B in an aqueous medium under visible light irradiation. The nanocomposites were prepared by a step-wise precipitation protocol. XPS analysis and active species trapping experiments demonstrated that the photocatalysis proceeded by a Z-scheme mechanism. Large scale aqueous medium molecular dynamics simulations showed that oxygen and CIP adsorb on the AgI part, while water interacts intensely with the CuWO4 component. Information from experimental and molecular dynamics studies was combined to arrive at the photocatalysis mechanism.