In situ formation of surface sulfide species and its role in enhancing the photocatalytic and photoelectrochemical properties of wide bandgap ZrO 2

A direct dual Z-scheme 3DOM SnS2-ZnS/ZrO2 composite with excellent photocatalytic degradation and hydrogen production performance

A novel direct dual Z-scheme 3DOM (three-dimensional ordered macropores) SnS₂-ZnS/ZrO₂ composite was prepared by the template method combined with the in situ sulfur replacement technology. The composition, structure, morphology, and surface physicochemical properties of the composites were well characterized. The results indicate that it possesses a uniform and periodical macroporous structure, a large surface area (121.1 m² g^-1), broad visible light absorption, and high separation ability of photoinduced electron/hole pairs. 3DOM SnS₂-ZnS/ZrO₂ composite removed 96.8% of methyl orange within 210 min of simulated sunlight irradiation. Moreover, photocatalytic hydrogen production achieved the rate of 928.1 μmol g^-1, which was 66.3 times as high as that of the commercial P25 after 8 h simulated sunlight irradiation. The enhanced photocatalytic performance mainly attributed to the direct dual Z-scheme system, which improves the charge separation efficiency and optimizes the charge transfer pathway. The charge transfer mechanism over the 3DOM SnS₂-ZnS/ZrO₂ is discussed in detail based on the results of radical trapping experiments. Our work paves a new way to design 3DOM materials with direct dual Z-scheme structure.

Study on degradation of diesel pollutants in seawater by composite photocatalyst MnO2/ZrO2

In this paper, the effectiveness of the composite photocatalyst was studied by using manganese dioxide (MnO₂)/zirconium dioxide (ZrO₂) to degrade diesel pollutants in seawater under visible light.The MnO₂/ZrO₂ photocatalyst was prepared by co-precipitation and characterized by scanning electron microscopy, X-ray powder diffraction, energy-dispersive spectroscopy and UV-Vis diffuse reflectance spectroscopy analysis. This is the first report on a comprehensive analytical study on the effect of various physio-chemical parameters on diesel degradation using the synthesized MnO₂/ZrO₂ photocatalysts. The effects of doping ratio of MnO₂/ZrO₂, dosage, initial diesel concentration, calcination temperature, concentration of H₂O₂ solutions and illumination time on the diesel degradation were investigated. The degradation of diesel pollution in seawater was optimized by orthogonal experiment. According to the results, the prepared samples were monoclinic form and the MnO₂ was successfully doped into the bulk ZrO₂. The absorption edge of the MnO₂/ZrO₂ photocatalysts exhibited red shift, and this red shifts imply enhanced photon absorption under visible light compared with the pure ZrO₂. The results showed that under optimum reaction conditions, the degradation rate can reach 92.92%. The result of this study will enable ZrO₂ to make more effective use of sunlight and improve the actual value of photocatalytic technology in the field of contaminant treatment.

Efficient removal of toxic organic dyes and photoelectrochemical properties of iron-doped zirconia nanoparticles

Iron (Fe)-doped ZrO₂ tetragonal nanoparticles were synthesized by a facile and inexpensive hydrothermal technique, that were doped with Fe³⁺ ions (0.1, 0.3, and 0.5 mol%) into the host lattice without altering the morphology and crystal structure of the nanoparticles. SEM and TEM investigations indicated that the morphology of ZrO₂ nanoparticles did not change even after incorporation of Fe, while the band gap of semiconducting ZrO₂ nanoparticles was reduced from 4.97 to 1.77 eV. Such a in band gap was responsible to harvest more photons to stimulate the generation of more electrons in the valence band, thereby enhancing the photoelectrochemical (PEC) water splitting as well as photocatalytic and photoelectrocatalytic activities in the photodegradation of Rhodamine B. The 0.3 mol%-doped ZrO₂ electrode showed enhanced photocurrent density (0.07 × 10^-3 A/cm²), that was 45-times greater than the pure sample. The electrochemical impedance spectroscopy (EIS) confirmed that 0.3 mol%-doped ZrO₂ exhibited the best charge transfer characteristics, which increased with PEC water splitting activity. The maximum photocurrent density and long-term photo-stability were achieved in the light on-off states.