Controlling Pt co-catalyst loading in a WO3 quantum dot and MoS2 nanosheet composite Z-scheme system for enhanced photocatalytic H2 evolution

Construction of WO3 nanocubes@Loess for rapid photocatalytic degradation of organics in wastewater under sunlight

In nowadays, environmental pollution has been greatly improved, but the development of low-cost and environmentally friendly materials are still challenge in the field of water treatment. Herein, a cheap and eco-friendly natural loess particle (LoP) was used for in situ growth of tungsten trioxide nanocubes (WO3NCs) on its surface via a simple one-pot hydrothermal method, which afforded a stable loess-based photocatalyst (WO3NCs@LoP). It was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) analysis, UV-Vis diffuse reflectance spectra (UV-Vis DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic performances of WO3NCs@LoP were applied to photodegradation of organics under visible-light illumination. It was found that the removal rate of methylene blue (MB) got to 99% within 20 min, which was higher than that of materials, such as pure LoP and WO3NCs. Moreover, the photocatalytic activity of WO3NCs@LoP remained 85% after 9 cycling times, indicating its high stability and reusability. It was suggested that the synergy of the well narrowed band gap and effectual control of e--h+ recombination in WO3NCs@LoP improve its photodegradation efficiency. In summary, using natural minerals (LoP) as carrier, a novel eco-friendly photocatalyst could be explored for photodegradation of organic pollutions in wastewater treatment.

Unique ternary Ni-MOF-74/Ni2P/MoSx composite for efficient photocatalytic hydrogen production: Role of Ni2P for accelerating separation of photogenerated carriers

A reasonable introduction of MOFs-derived Ni₂P with high dispersity is a valid way to reduce the recombination rate of photogenerated electron-holes, thus for more effective visible-light-driven water splitting. In this study, Ni-MOF-74/Ni₂P precursor was obtained by low-temperature phosphating method. A ternary heterojunction Ni-MOF-74/Ni₂P/MoS_x with a unique structure is obtained by a solution-based mixing method. The unique structure of Ni-MOF-74/Ni₂P provides advantages for MoS_x load. The UV-visible diffuse reflectance spectroscopy proves that the introduction of Ni₂P improves the utilization of visible light by the composite catalyst 10%-NPMS and promotes more electrons generation, thereby improving photocatalytic hydrogen production activity. It is proved that the introduced Ni₂P can accelerate the separation of photogenerated carriers by characterization (PL, EIS, LSV, etc.) analyses. The composite catalyst 10%-NPMS with the best hydrogen production activity was obtained by adjusting the ratio between Ni-MOF-74/Ni₂P and MoS_x. The photocatalytic hydrogen evolution of the composite catalyst 10%-NPMS (286.16 μmol) is 28.30, 2.78, 3.79 and 2.41 times that of pure Ni-MOF-74, Ni₂P, MoS_x and binary 10%-Ni-MOF-74/MoS_x within 5 h, respectively. And the hybrid 10%-Ni-MOF-74/Ni₂P/MoS_x exhibits excellent photocatalytic hydrogen evolution performance and good stability. This research will provide a new strategy for synthesizing unique ternary composite materials by using metal organic framework materials as precursors.

Efficient hydrogen generation of vector Z-scheme CaTiO3/Cu/TiO2 photocatalyst assisted by cocatalyst Cu nanoparticles

Herein, the CaTiO₃/Cu/TiO₂ all-solid-state Z-scheme heterojunction is successfully designed via Cu nanoparticles situating at the interface between CaTiO₃ and TiO₂ with a new synthesis route. Interestingly, TiO₂ nanosheets are generated in-situ on the surface of CaTiO₃ in the second step hydrothermal reaction. The lifetimes of photoexcited carriers, photoluminescence emission spectra and transient photocurrent response tests have confirmed that the efficient Z-scheme charge transmission path of the CaTiO₃/Cu/TiO₂ is beneficial to facilitate the separation of photogenerated carriers and reduce their recombination efficiency. As expected, the hydrogen generation rate of CaTiO₃/Cu/TiO₂ is increased to 23.550 mmol g^-1h^-1 with the appropriate amount of copper loading, which is about 981 times and 93 times higher than that of pristine CaTiO₃ (0.024 mmol g^-1h^-1) and CaTiO₃/TiO₂ (0.253 mmol g^-1h^-1), respectively. Furthermore, the CaTiO₃/Cu/TiO₂ sample shows good stability in cycle experiments. Particularly, experimental results show that the non-noble metal Cu nanoparticles can be an effective electron mediator. And these merits strongly demonstrate that the CaTiO₃/Cu/TiO₂ composites have potential application in photocatalytic field. This study can provide fundamental guidance for designing rationally efficient non-noble metal vector Z-scheme system photocatalysts with outstanding photocatalytic H₂ generation performance.

Recent Progress of Transition Metal Phosphides for Photocatalytic Hydrogen Evolution

Photocatalytic hydrogen evolution can effectively alleviate the troublesome global energy crisis by converting solar energy into the chemical energy of hydrogen. In order to realize efficient hydrogen generation, a variety of semiconductor materials have been extensively investigated, including TiO₂ , CdS, g-C₃ N₄ , metal-organic frameworks (MOFs), and others. In recent years, to achieve higher photocatalytic performance and reach the level of large-scale industrial applications, photocatalysts decorated with transition metal phosphides (TMPs) have shone brightly because of their low cost, stable physical and chemical properties, and substitution for precious metals of TMPs. This Review highlights the preparation methods and properties associated with photocatalysis of TMPs. Moreover, the H₂ generation efficiency of photocatalysts loaded with TMPs and the roles of TMPs in catalytic systems are also studied systematically. Apart from being co-catalysts, several TMPs can also serve as host catalysts to boost the activity of photocatalytic composites. Finally, the development prospects and challenges of TMPs are put forward, which is valuable for future researchers to expand the application of TMPs in photocatalytic directions and to develop more active photocatalytic systems.

Bi and oxygen defects improved visible light photocatalysis with BiOBr nanosheets

Bi metal attached BiOBr with oxygen defect (BiOBr(3)-Bi(x%, x = 10, 20, 30)) nanosheets was prepared via the hydrothermal process in this study. The different characterization techniques of x-ray diffraction, x-ray photoelectron spectrometer, electron spin resonance (ESR), field emission scanning electron microscope, and high resolution transmission electron microscope were used to distinguish the composition, crystal structure, and morphology of the samples. Under visible light irradiation, the BiOBr(3)-Bi(x%, x = 10, 20, 30) samples exhibited improved photocatalytic activity for the degradation of colored dyes (RhB) and colorless tetracycline hydrochloride. Such an improvement was ascribed to the widened visible light absorption and enhanced separation of the photogenerated electron-hole pairs because of the synergistic effect of oxygen vacancies and Bi metal with plasmon resonance effects. A possible photocatalytic mechanism of the quasi Z-scheme process was proposed on the basis of ESR measurements and radical-trapping experiments.