Fabrication of ion doped WO3 photocatalysts through bulk and surface doping

Modulating the Moderate d-Band Center of Indium in InVO4 Nanobelts by Synergizing MnOx and Oxygen Vacancies for High-Efficiency CO2 Photoreduction

Modulating the electronic properties of transition metal sites in photocatalysts at the atomic level is essential for achieving high-activity carbon dioxide photoreduction (CO2PR). An electronic strategy is herein proposed to engineer In-d-band center of InVO4 by incorporating MnOx nanoparticles and oxygen vacancies (VO) into holey InVO4 nanobelts (MnOx/VO-InVO4), which synergistically modulates the In-d-band center to a moderate level and consequently leads to high-efficiency CO2PR. The MnOx/VO-InVO4 catalyst with optimized electronic property exhibits a single carbon evolution rate of up to 145.3 µmol g-1 h-1 and a carbon monoxide (CO) product selectivity of 92.6%, coming out in front of reported InVO4-based materials. It is discovered that the modulated electronic property favors the interaction between the In sites and their intermediates, which thereby improves the thermodynamics and kinetics of the CO2PR-to-CO reaction. This work not only demonstrates the effective engineering of the d orbital of the low-coordination In atoms to promote CO2PR, but also paves the way for the application of tuning d-band center to develop high-efficiency catalysts.

Modulating the doping state of transition metal ions in ZnS for enhanced photocatalytic activity

Transition metal ions (M = Ag+, Cu2+, Co2+, and Cr3+) are surface or homogeneously doped into ZnS via facile cation-exchange reaction, and while Ag+ and Cu2+ doping does not induce sulphur vacancies (Vs) or zinc vacancies (VZn), Co2+ and Cr3+ doping induces Vs. The surface doped catalysts exhibit greatly higher activity than the ZnS and homogenous doped catalysts for H2 evolution and CO2 reduction. The important role of the doping state on affecting the photo-absorption, carrier separation efficiency, and photoreaction kinetics has been systemically investigated and proposed. This work sheds light on the future design and fabrication of high-performance photocatalysts by element doping.

Fabrication of zirconium-based metal-organic frameworks@tungsten trioxide (UiO-66-NH2@WO3) heterostructure on carbon cloth for efficient photocatalytic removal of tetracycline antibiotic under visible light

Designing recyclable photocatalysts with high activity and stability has drawn considerable attention in the fields of sewage treatment. Herein, a series of heterojunctions constructed by zirconium-based metal-organic frameworks (UiO-66-NH₂) and tungsten trioxide (WO₃) is immobilized on carbon cloth via a facile solvothermal method, resulting in highly recyclable photocatalysts. Multiple characterization techniques, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy, verify the successful synthesis of UiO-66-NH₂ nanospheres on the surface of needlelike WO₃ modified carbon cloth. Results show that the optimal heterojunction photocatalyst exhibits excellent photocatalytic degradation efficiency for the removal of tetracycline (TC) from water, for which nearly 100% of TC is degraded within 60 min under visible light. Trapping experiments and electron spin resonance (ESR) spectra analyses demonstrate that the superoxide radicals O₂^- and photogenerated hole h⁺ play a dominant role in the degradation process. Excellent photocatalytic activity is dominantly attributed to the effective separation of photoinduced carriers in this type-Ⅱ heterostructure system. Moreover, the possible photocatalytic oxidation degradation pathway is confirmed by analyzing intermediates using liquid chromatography mass spectrometry (LC-MS). This study offers a highly efficient strategy to design recyclable heterojunction photocatalysts for the degradation of refractory antibiotics in sewage.

In situ preparation of g-C3N4/Bi4O5I2 complex and its elevated photoactivity in Methyl Orange degradation under visible light

A graphite carbon nitride (g-C₃N₄) modified Bi₄O₅I₂ composite was successfully prepared in-situ via the thermal treatment of a g-C₃N₄/BiOI precursor at 400°C for 3 hr. The as-prepared g-C₃N₄/Bi₄O₅I₂ showed high photocatalytic performance in Methyl Orange (MO) degradation under visible light. The best sample presented a degradation rate of 0.164 min^-1, which is 3.2 and 82 times as high as that of Bi₄O₅I₂ and g-C₃N₄, respectively. The g-C₃N₄/Bi₄O₅I₂ was characterized by X-ray powder diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectra (DRS), electrochemical impedance spectroscopy (EIS) and transient photocurrent response in order to explain the enhanced photoactivity. Results indicated that the decoration with a small amount of g-C₃N₄ influenced the specific surface area only slightly. Nevertheless, the capability for absorbing visible light was improved measurably, which was beneficial to the MO degradation. On top of that, a strong interaction between g-C₃N₄ and Bi₄O₅I₂ was detected. This interplay promoted the formation of a favorable heterojunction structure and thereby enhanced the charge separation. Thus, the g-C₃N₄/Bi₄O₅I₂ composite presented greater charge separation efficiency and much better photocatalytic performance than Bi₄O₅I₂. Additionally, g-C₃N₄/Bi₄O₅I₂ also presented high stability. •O₂^- and holes were verified to be the main reactive species.

Facile synthesis of a WOx/CsyWO3 heterostructured composite as a visible light photocatalyst

In this work, a WO_x/Cs_yWO₃ heterostructured composite was synthesized via a simple pyrolysis method followed by heat treatment under a reducing atmosphere. Optical absorption results revealed the WO_x/Cs_yWO₃ heterostructured composite exhibits a strong absorption tail in the Vis and NIR regions which could have important implications for its photoactivity. The photocatalytic performance of synthesized samples with different Cs/W molar ratios was evaluated by the photodegradation of RhB in aqueous solution under simulated solar light irradiation. The results revealed that the photocatalytic activity of the WO_x/Cs_yWO₃ composite is much higher than those of pure tungsten bronze (Cs_xWO₃, x = 0.32, and 0.5) and pure WO_2.83 samples, where 90% RhB was degraded after 160 min irradiation. Also, the WO_x/Cs_yWO₃ composite exhibits excellent photocatalytic activity for the degradation of MO, MB, RhB, and MG aqueous solution under visible light irradiation. It is proposed that the higher photocatalytic activity of the WO_x/Cs_yWO₃ composite could be attributed to the greater surface adsorption of dye molecules, intense light absorption in the visible and NIR regions, and photogenerated electron–hole separation.

In this work, a WO_x/Cs_yWO₃ heterostructured composite photocatalyst was synthesized via a simple pyrolysis method followed by heat treatment under a reducing atmosphere.

Synthesis of Mo-doped WO3 nanosheets with enhanced visible-light-driven photocatalytic properties

Ion doping provides a powerful means for the fabrication of a functionalized photocatalyst that is both active and stable.