One-Pot Hydrothermal Synthesis of La-Doped ZnIn2S4 Microspheres with Improved Visible-Light Photocatalytic Performance

A review on potential sulfide-based ternary chalcogenides for emerging photo-assisted water purification applications

Sulfide-based ternary chalcogenides have been recognized widely as exceptional photocatalysts, thanks to their narrow band gap enabling them to harvest solar energy to the maximum extent. They provide excellent optical, electrical, and catalytic performance and are of abundant use as a heterogeneous catalyst. Among sulfide-based ternary chalcogenides, compounds exhibiting AB2X4 structure form a new class of materials with excellent stability in photocatalytic performance. In the AB2X4 family of compounds, ZnIn2S4 is one of the top performing photocatalyst for energy and environmental applications. However, to date, only limited information is available on the mechanism behind the photo-induced migration of charge carriers in ternary sulfide chalcogenides. Ternary sulfide chalcogenides with their visible region activity and substantial chemical stability greatly depend on crystal structure, morphology, and optical characteristics for their photocatalytic activity. Hence, in this review, a comprehensive assessment of the reported strategies for enhancement of the photocatalytic efficiency of this compound is presented. In addition, a meticulous investigation of the applicability of ternary sulfide chalcogenide compound ZnIn2S4, in particular, has been delivered. Also, the photocatalytic behavior of other sulfide-based ternary chalcogenides for water remediation applications has also been briefed. Finally, we conclude with an insight into the challenges and future advancements in the exploration of ZnIn2S4-based chalcogenide as a photocatalyst for various photo-responsive applications. It is believed that this review could contribute to a better understanding of ternary chalcogenide semiconductor photocatalysts for solar-driven water treatment applications.

Nb, Se-codoped ZnIn2S4/NbSe2composites with enhanced catalytic activity and photodegradation performance towards tetracycline

Low quantum efficiency and serious photogenerated carrier recombination have been urgent bottleneck problems for photocatalytic materials. Herein, we prepared Nb, Se-codoped ZnIn₂S₄/NbSe₂composites through a facile solvothermal method. The synergetic effect of codoping and cocatalyst was investigated on the photodegradation performance towards tetracycline under visible-light irradiation. By adjusting the final composition, the comprehensive characterization revealed that the optimum degradation efficiency of NS/ZIS-1.6 catalyst arrived at 75% in 70 min, which was 5.8 times higher than that of pure ZnIn₂S₄. Deep analysis indicated that the enhanced photocatalytic performance could be attributed to higher light absorption, more efficient electron/hole separation, faster charge transport, and lower carrier recombination. This work may offer novel viewpoint for design of high-performance catalysts towards the visible-light-driven photodegradation system.

Cyclodextrin functionalization enhancement in a CA-β-CD/g-C3N4/Ag2CO3 Z-type heterojunction towards efficient photodegradation of organic pollutants

More free radicals can be produced quickly by CA-β-CD/CN/Ag2CO3, leading to more effective and stable photocatalytic activity. The interfacial charge separation has been improved by the CA-β-CD modified CN/Ag2CO3 heterojunction.

Surface Coordination of Pd/ZnIn2S4 toward Enhanced Photocatalytic Activity for Pyridine Denitrification

New surface coordination photocatalytic systems that are inspired by natural photosynthesis have significant potential to boost fuel denitrification. Despite this, the direct synthesis of efficient surface coordination photocatalysts remains a major challenge. Herein, it is verified that a coordination photocatalyst can be constructed by coupling Pd and CTAB-modified ZnIn₂S₄ semiconductors. The optimized Pd/ZnIn₂S₄ showed a superior degradation rate of 81% for fuel denitrification within 240 min, which was 2.25 times higher than that of ZnIn₂S₄. From the in situ FTIR and XPS spectra of 1% Pd/ZnIn₂S₄ before and after pyridine adsorption, we find that pyridine can be selectively adsorbed and form Zn⋅⋅⋅C-N or In⋅⋅⋅C-N on the surface of Pd/ZnIn₂S₄. Meanwhile, the superior electrical conductivity of Pd can be combined with ZnIn₂S₄ to promote photocatalytic denitrification. This work also explains the surface/interface coordination effect of metal/nanosheets at the molecular level, playing an important role in photocatalytic fuel denitrification.

Highly Efficient Photocatalytic Hydrogen Evolution over Mo-Doped ZnIn2S4 with Sulfur Vacancies

The introduction of impure atoms or crystal defects is a promising strategy for enhancing the photocatalytic activity of semiconductors. However, the synergy of these two effects in 2D atomic layers remains unexplored. In this case, the preparation of molybdenum-doped thin ZnIn₂S₄-containing S vacancies (Mo-doped Sv-ZnIn₂S₄) is conducted using a one-pot solvothermal method. The coordination of Mo doping and S vacancies not only enhances visible light absorption and facilitates the separation of photogenerated carriers but also provides many active sites for photocatalytic reactions. Meanwhile, the Mo-S bonds play function as high-speed channels to rapidly transfer carriers to the active sites, which can directly promote hydrogen evolution. Consequently, Sv-ZnIn₂S₄ with an optimized amount of Mo doping exhibits a high hydrogen evolution rate of 5739 μmol g^-1 h^-1 with a corresponding apparent quantum yield (AQY) of 21.24% at 420 nm, which is approximately 5.4 times higher than the original ZnIn₂S₄. This work provides a new strategy for the development of highly efficient and sustainable 2D atomic photocatalysts for hydrogen evolution.

Fabrication of a Heterobinuclear Redox Cycle to Enhance the Photocatalytic Activity of BiOCl

La3+ and Ni2+-doped BiOCl were prepared by sol–gel method and characterized by physicochemical and spectroscopic techniques. Their photocatalytic performances were investigated by the degradation of gentian violet under visible light. The results indicated that the co-doping of Ni and La significantly enhanced the photocatalytic performance of BiOCl. The photodegradation efficiency of LaNiBiOCl reached 95.5% in 105 min, which was 1.5 times that of BiOCl. This significant enhancement in photocatalytic activity was mainly attributed to the effective capture and transfer of photogenerated electrons between heterobinuclear La and Ni redox cycle, which benefited the photodegradation of active h+ and the formation of active •O2−. Furthermore, the photodegradation activity did not show an obvious drop after five recycles, indicating that LaNiBiOCl was a promising semiconductor photocatalyst for the degradation of gentian violet.

Preparation, Characterization of ZnTiO3/ZnO Composite Materials and Their Photocatalytic Performance

With zinc acetate and butyl titanate as raw materials, pure ZnO and ZnTiO₃/ZnO composite photocatalysts were synthesized by a sol-gel method and calcined at 550 °C. The crystal structure, morphology, surface area, optical property, and element valence states of samples were characterized and the photocatalytic activity of the prepared photocatalysts were assessed by the degradation of rhodamine B. Results show that the crystal structure of ZnO is a hexagonal wurtzite phase with a band gap of 3.20 eV. When the Zn/Ti molar ratio reaches 0.2, ZnTiO₃ phase appears and ZnTiO₃/ZnO composite forms, which advances the transfer of photogenerated charges. ZnTiO₃/ZnO (Ti/Zn = 0.2) exhibits the highest photocatalytic activity, and the degradation degree of RhB reaches 99% after 60 min, which is higher than that of pure ZnO (90%). An exorbitant Ti/Zn molar ratio will reduce the crystallinity and form more amorphous components, which is not conducive to photocatalytic performance. Therefore, when the Ti/Zn molar ratio exceeds 0.2, the photocatalytic activities of ZnTiO₃/ZnO composites decrease.

Ag Decoration and SnO2 Coupling Modified Anatase/Rutile Mixed Crystal TiO2 Composite Photocatalyst for Enhancement of Photocatalytic Degradation towards Tetracycline Hydrochloride

The anatase/rutile mixed crystal TiO2 was prepared and modified with Ag decoration and SnO2 coupling to construct a Ag@SnO2/anatase/rutile composite photocatalytic material. The crystal structure, morphology, element valence, optical properties and surface area were characterized, and the effects of Ag decoration and SnO2 coupling on the structure and photocatalytic properties of TiO2 were studied. Ag decoration and SnO2 coupling are beneficial to reduce the recombination of photogenerated electrons and holes. When the two modification are combined, a synergistic effect is produced in suppressing the photogenerated charge recombination, making Ag@SnO2/TiO2 exhibits the highest quantum utilization. After 30 min of illumination, the degradation degree of tetracycline hydrochloride (TC) by pure TiO2 increased from 63.3% to 83.1% with Ag@SnO2/TiO2.

Rational Design and Synthesis of ZnWO4 Nanorods Decorated with SnS Nanodots with Enhanced Visible-Light Photocatalytic Performance

Aiming to construct a direct Z-scheme binary heterostructure for efficient degradation of the organic dye Rhodamine B (RhB), ZnWO4 nanorods decorated with SnS nanodots were rationally designed and prepared via a facile two-step route. Morphological observation and structural study showed that ultra-fine SnS nanodots were anchored on the surface of ZnWO4 nanorods to form an intimate contact between the two components. Such a special structure provided SnS/ZnWO4 nanocomposites with significantly enhanced light harvesting capacity, revealed by the results of UV-vis diffuse reflection spectroscopy (DRS). Photoluminescence (PL) analysis in combination with electrochemical measurements demonstrated that the recombination of photoactivated charge carriers was efficiently inhibited and the transfer of photoactivated charge carriers was successfully achieved due to the introduction of SnS. The degradation rate over SnS/ZnWO4 nanocomposites reached a maximum value at SnS content of 9 wt%. The significantly enhanced photoactivity of SnS/ZnWO4 nanocomposites was imputed to the synergistic effect of the promoted light absorption ability and effective photogenerated charge carriers’ transfer and separation.