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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]

Water splitting using solar light and an efficient photocatalyst is one of the new methods of hydrogen production that has attracted much attention today because of its importance in the energy crisis. Hence, a composite material containing molybdenum disulfide (MoS2) and g-C3N4 was synthesized and used in the photocatalytic process. For this purpose, in the first instance, the photocatalytic activity of MoS2/g-C3N4 was confirmed by the decolorization pathway of Rhodamine B (Rh B) under visible light irradiation. Then, MoS2/g-C3N4 was carefully identified by SEM, XRD, PL, UV–Vis, EDS, and FT-IR analysis. Results of characteristic peaks and composite surface morphology confirm that the structural integrity of the primary photocatalyst sample was intact after combination with MoS2 despite chemical interactions. The Brunner–Emmet–Teller (BET) surface area, total per valume, and average pore diameter of the sample are close to 15 m2g−1, 0.07 cm3g−1, and 19.5 nm, respectively. Then, the hydrogen production process under solar light was simulated using MoS2/g-C3N4 photocatalyst and the Production rate was measured using a gas chromatography system (GC). In addition, the Eosin-Y dye solution is also used as a sensitizer to increase the photocatalyst activity under visible light. The g-C3N4/MoS2-Triethanolamine (TEOA) mixture showed the best quantum efficiency when compared to all other sacrificial agents. Investigation of the factors affecting the catalyst activity showed that the parameters of exposure time, the concentration of photocatalyst, and triethanolamine (TEOA) percent used as a sacrificial agent affect water-splitting reaction efficiency. Further measurements showed that the highest hydrogen production rate of 1905 µmol g−1 h−1 is accessible. Accordingly, the g-C3N4 composite with MoS2 can be a promising photocatalyst for high-efficiency water splitting. Besides, the photocatalytic mechanism is demonstrated to well-fit into the S-scheme pathway with apparent evidence. [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]