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The activation capacity of molecular oxygen is an important indicator to evaluate the photocatalytic efficiency of photocatalysts. In this paper, WS2 nanosheet was deposited on hyper-crosslinked CTF-1-G (obtained by molecular expansion from covalent triazine framework CTF-1) to form a C-GW heterojunction, which promoted the photodegradation of pollutants and the activation of molecular oxygen. This novel C-GW heterojunction exhibited excellent degradation property for organic pollutants (tetracycline (TC), rhodamine B (RhB)) and activating molecular oxygen under visible light irradiation. Among them, C-GW15 could degrade 98% of 20 ppm TC in 60 min and 99% of 30 ppm RhB in 30 min, and it had the highest hydrogen generation rate and hydrogen production amount in 4 hours, which were 8.74 mmol h−1 g−1 and 34.94 mmol g−1, respectively. Meanwhile, C-GW15 had the strongest 3,3′,5,5′-tetramethylbenzidine oxidation capacity and could generate 1.83 μmol of ˙O2− in 60 min and the production of H2O2 was 20.8 μmol L−1 in 40 min. The results of this study clearly indicated that the combination of WS2 and CTF-1-G can enhance the visible light absorption capacity and photogenerated carrier separation efficiency, thus promoting the photocatalytic performance. Finally, a Z-type photocatalytic mechanism was proposed based on radical capture, molecular oxygen activation experiments and electron spin resonance analysis. These findings will extend the fundamental understanding of the Z-type photocatalytic mechanism and provide new opportunities for the rational design of CTF heterojunctions for the treatment of environmental pollution and clean energy conversion. [ABSTRACT FROM AUTHOR]

Photocatalytic splitting of water for hydrogen generation is a green and renewable solution for converting solar energy to chemical energy; thus, the development of high-performance and stable photocatalytic materials has emerged as a research hotspot recently. Herein, a heterostructure composite photocatalyst of octahedral CoO uniformly modified with novel nitrogen-doped MXene quantum dots (N-MQDs) is successfully designed using a typical solvothermal approach. The optimum photocatalytic hydrogen evolution efficiency of the prepared N-MQDs@CoO heterojunction composite is 82.54 μmol g−1 h−1 with visible light, which is 16.57 times higher compared to the pure CoO. A series of photoelectrochemical tests were further performed to elucidate the photocatalytic hydrogen evolution mechanism. The remarkable improvement of activity is primarily attributed to the synergistic interaction between the closely spaced interface contacts and energy level matching among high conductivity Ti3C2 MXene quantum dots with CoO octahedra, dramatically hastening the segregation and transfer of photo-generated carriers. This study provides new ideas for the construction of MXene quantum dot-based co-photocatalysts with highly efficient photocatalytic performance and stability toward solar energy conversion applications. [ABSTRACT FROM AUTHOR]

In this paper, CdS QDs@ZrO 2 –TiO 2 hollow spherical composites with double Z-scheme heterostructure modified by CdS QDs were prepared by the sol–gel method and vacuum impregnation method using polystyrene (PS) microspheres synthesized by the self-assembly technique as templates. A series of characterization results show that CdS QDs@ZrO 2 –TiO 2 composites treated by PS microspheres have the structure of hollow spheres with uniform size and orderly arrangement. Moreover, the double Z-scheme heterojunction formed between CdS QDs, ZrO 2 , and TiO 2 in the composite can optimize the charge transfer path and improve the charge separation efficiency. Results of the photodegradation and the photo-splitting water of CdS QDs@ZrO 2 –TiO 2 composites show that, compared with other systems, CdS QDs@ZrO 2 –TiO 2 composites have the highest photocatalytic degradation rate of crystal violet, and meanwhile, the photocatalytic hydrogen production rate of the composite under simulated sunlight is more than 100 times that of TiO 2. The good absorption of visible light, the successful construction of double Z-scheme heterojunction, and the unique hollow sphere structure of CdS QDs@ZrO 2 –TiO 2 composites are the key factors for enhanced photocatalytic performance. The preparation of CdS QDs@ZrO 2 –TiO 2 hollow spherical composite material with PS microspheres as templates not only expands its photoresponse range, but also optimizes the charge transfer path and improves the separation efficiency of electron–hole pairs by the construction of double Z-scheme heterojunction. [Display omitted] • CdS QDs@ZrO 2 –TiO 2 hollow spherical composite was prepared using PS microspheres as templates. • Hollow spherical CdS QDs@ZrO 2 –TiO 2 is not only uniform in spherical size, but also in neat and orderly arrangement. • Successful construction of double Z-scheme heterojunction improves charge separation efficiency. • The addition of CdS QDs expands the visible light response range. • CdS QDs@ZrO 2 –TiO 2 exhibits the highest photocatalytic activity compared with TiO 2 , @TiO 2 , and @ZrO 2 –TiO 2. [ABSTRACT FROM AUTHOR]

The rapid recombination of photogenerated carriers and strong photocorrosion have considerably limited the practical application of CdS in the field of photocatalysis. Loading a cocatalyst has been widely utilized to largely enhance photocatalytic activity. In the present work, a WC@C cocatalyst was prepared by a novel molten salt method and explored as an efficient noble-metal-free cocatalyst to significantly enhance the photocatalytic hydrogen evolution rate of CdS nanorods. The WC@C/CdS composite photocatalyst with a 7 wt% content of WC@C showed the highest photocatalytic hydrogen evolution rate of 8.84 mmol g−1 h−1, which was about 21 and 31 times higher than those of CdS and 7 wt% Pt/CdS under visible light irradiation. A high apparent quantum efficiency (AQY) of 55.28% could be achieved under 420 nm monochromatic light. Furthermore, the photocatalytic activity of the 7 wt% WC@C/CdS photocatalyst exhibited good stability for 12 consecutive cycles of the photocatalytic experiment with a total reaction time of 42 h. The excellent photocatalytic performance of the photocatalyst was attributed to the formation of a Schottky junction and the loading cocatalyst, which not only accelerated the separation of the photogenerated carrier but also provided a reactive site for hydrogen evolution. This work revealed that WC@C could act as an excellent cocatalyst for enhancing the photocatalytic activity of CdS nanorods. [ABSTRACT FROM AUTHOR]

Constructing heterostructures with efficient charge separation is a promising route to improve photocatalytic hydrogen production. In this paper, MoS x /CdS/KTaO 3 ternary heterojunction photocatalysts were successfully prepared by a two-step method (hydrothermal method and photo deposition method), which improved the photocatalytic hydrogen evolution activity. The results show that the rate of hydrogen evolution for the optimized photocatalyst is 2.697 mmol g−1·h−1under visible light, which is 17 times and 2.6 times of the original CdS (0.159 mmol g−1 h−1) and the optimal CdS/KTaO 3 (1.033 mmol g−1 h−1), respectively, and the ternary photocatalyst also shows good stability. The improvement on photocatalytic hydrogen evolution performance can be attributed to the formation of heterojunction between the prepared composite materials, which effectively promotes the separation and migration of photo-generated carriers. Amorphous MoS x acts as an electron trap to capture photogenerated electrons, providing active sites for proton reduction. This provides beneficial enlightenment for hydrogen production by efficiently utilizing sunlight to decompose water. • Successful preparation of a novel MoS x cocatalyst-modified CdS/KTO heterostructure without noble metals. • Composite catalysts exhibit excellent photocatalytic hydrogen evolution performance. • The hydrogen production rate of the composite is 17 times and 2.6 times that of pure CdS and CdS/KTO. • Amorphous MoS x acts as a trap to capture photogenerated electrons, providing active sites for proton reduction. [ABSTRACT FROM AUTHOR]

The study of environmentally friendly semiconductor photocatalysts has important practical significance for efficient photocatalytic hydrogen evolution. In this experiment, type II heterojunction NiCo-LDH/CeO2 was prepared by in situ loading, and the NiCo-LDH/CeO2 catalyst showed good activity under simulated sunlight irradiation. Under simulated visible light irradiation, its hydrogen production rate reached 2.7 mmol h−1 g−1, which was higher than that of NiCo-LDH (0.86 mmol h−1 g−1). Through a series of characterization data, it can be concluded that the heterojunction successfully constructed by the close contact between NiCo-LDH and CeO2 accelerates the separation of photogenerated electrons and holes and can effectively inhibit the recombination of the two so that more electrons are involved in the hydrogen evolution reaction. The material has good interfacial charge transfer performance, which improves the photocatalytic performance. This work can provide an effective method for the research and development of NiCo-LDH. [ABSTRACT FROM AUTHOR]

In the field of photocatalysis, building a heterojunction is an effective way to promote electron transfer and enhance the reducibility of electrons. Herein, the S‐scheme heterojunction photocatalyst (CoS2/Zn0.5Cd0.5S) of CoS2 nanospheres modified Zn0.5Cd0.5S solid solution was synthesized and studied. The H2 evolution rate of the composite catalyst reached 25.15 mmol g−1 h−1, which was 3.26 times that of single Zn0.5Cd0.5S, whereas pure CoS2 showed almost no hydrogen production activity. Moreover, CoS2/Zn0.5Cd0.5S had excellent stability and the hydrogen production rate after six cycles of experiments only dropped by 6.19 %. In addition, photoluminescence spectroscopy and photoelectrochemical experiments had effectively proved that the photogenerated carrier transfer rate of CoS2/Zn0.5Cd0.5S was better than CoS2 or Zn0.5Cd0.5S single catalyst. In this study, the synthesized CoS2 and Zn0.5Cd0.5S were both n‐type semiconductors. After close contact, they followed an S‐scheme heterojunction electron transfer mechanism, which not only promoted the separation of their respective holes and electrons, but also retained a stronger reduction potential, thus promoting the reduction of H+ protons in photocatalytic experiments. In short, this work provided a new basis for the construction of S‐scheme heterojunction in addition to being used for photocatalytic hydrogen production. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen evolution is a promising method to convert solar energy. Here, the heterojunction structure of g‐C3N4/CdS was modified by NiCoP prepared by one‐step method for the first time, and the photocatalyst NiCoP‐g‐C3N4/CdS was successfully designed and prepared, which can effectively separate and transfer photogenerated electrons and efficient hydrogen evolution under visible light. Moreover, NiCoP‐g‐C3N4/CdS photocatalyst has abundant surface‐active sites, and its photocatalytic hydrogen evolution performance has been greatly improved. When NiCoP content was 5 % in NiCoP‐g‐C3N4/CdS, the catalytic activity was the highest, and the hydrogen production rate reached an astonishing 55.63 mmol h−1 g−1, which was 23.35 times that of CdS (2.38 mmol h−1 g−1) and 11.51 times that of g‐C3N4/CdS (4.84 mmol h−1 g−1). In addition, NiCoP‐g‐C3N4/CdS photocatalyst has excellent stability for hydrogen production. The materials were characterized and analyzed by XRD, SEM, TEM, XPS, UV‐Vis DRS, FTIR, UPS, N2 adsorption‐desorption process and electrochemical test etc. At the same time, the possible mechanism of NiCoP‐g‐C3N4/CdS photocatalytic hydrogen production reaction is proposed. This study provides a new idea for the rational design of heterojunction photocatalyst and transition metal phosphide cocatalyst. [ABSTRACT FROM AUTHOR]

Atomically thin two-dimensional (2D) CN sheets have attracted extensive attention in the field of photocatalysis because of their shorter diffusion path of photogenerated carriers and abundant surface reaction sites than bulk CN. However, 2D CNs still exhibit poor visible-light photocatalytic activity because of a strong quantum size effect. Here, PCN-222/CNs vdWHs were successfully constructed using the electrostatic self-assembly method. The results showed that PCN-222/CNs vdWHs with 1 wt.% PCN-222 enhanced the absorption range of CNs from 420 to 438 nm, which improved the absorption capacity of visible light. Additionally, the hydrogen production rate of 1 wt.% PCN-222/CNs is four times that of the pristine 2D CNs. This study provides a simple and effective strategy for 2D CN-based photocatalysts to promote visible light absorption. [ABSTRACT FROM AUTHOR]

BACKGROUND: A Z‐scheme structured photocatalyst is a highly efficient photocatalyst for hydrogen evolution and degradation of pollutants. RESULTS: An indirect Z‐scheme heterojunction g‐C3N4/CQDs/InVO4 with carbon quantum dots (CQDs) as electron mediator was constructed and was successfully synthesized using a facile hydrothermal method. The photocatalytic activity of the as‐prepared composite was evaluated in terms of hydrogen generation and degradation of rhodamine B (RhB) dye. The as‐prepared sample CV20/CQDs2 (g‐C3N4/2 wt% CQDs/20 wt% InVO4) exhibits the best photocatalytic activity towards hydrogen production and RhB degradation. Within 90 min, 99.6% of RhB is removed, and the degradation rate constant of RhB over CV20/CQDs2 is 0.06491 min−1, which is 43.9, 6.64 and 3.3 times as high as that of InVO4, g‐C3N4 and binary composite g‐C3N4/InVO4. CV20/CQDs2 exhibits H2 evolution rate of 2.169 mmol g−1 h−1, which is 26.07, 2.65 and 1.6 times as high as that of InVO4, g‐C3N4 and g‐C3N4/InVO4. CONCLUSIONS: The enhanced photocatalytic activity is attributed to two aspects. First, CQDs, as electron mediator, promote the effective separation of photogenerated electrons and holes through Z‐scheme charge transfer pathway, preserving the high redox ability of electrons and holes. Second, g‐C3N4/CQDs/InVO4 shows strong optical absorption in the full visible‐light region. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]