The hydrophobicity of MoS 2 /g-C 3 N 4 based photocatalysts remains a major hurdle to their successful application for the remediation of water-soluble contaminants such as herbicides and heavy metals. Herein, we develop new photocatalysts based on the graft of three different cyclodextrins (α-CD, β-CD and γ-CD) on MoS 2 /g-C 3 N 4 composites (CDs/MoS 2 /g-C 3 N 4 ) for the removal of glyphosate and Cr (VI) from simulated agricultural runoff. CDs/MoS 2 /g-C 3 N 4 show remarkably enhanced photocatalytic activities for glyphosate degradation and Cr (VI) reduction compared to pristine MoS 2 /g-C 3 N 4 . In addition, γ-CD/MoS 2 /g-C 3 N 4 exhibits the highest hydrophilicity and photocatalytic activity among these three different cyclodextrins grafted MoS 2 /g-C 3 N 4 . The mechanistic investigation indicates that cyclodextrins can not only increase the accumulation of glyphosate and Cr (VI) onto the surface of CDs/MoS 2 /g-C 3 N 4 but also facilitate the fleet separation of photo-induced electron-hole pairs. In summary, these results collectively imply that the graft of cyclodextrins could be an effective strategy to improve the photocatalytic efficiency of MoS 2 /g-C 3 N 4 composites for the removal of glyphosate and Cr (VI) from simulated agricultural runoff.
In this paper, 1T/2H mixed-phase MoS 2 /g-C 3 N 4 composites (1T/2H-MG) were successfully synthesized by a simple two-step calcination method and used for Cr(VI) removal from aqueous environment. A series of characterization methods were used to characterize the microstructure and surface morphology of the prepared materials. The experiment results showed that 1T/2H-MG (1:12) composite with good pH and temperature adaptability could completely remove Cr(VI) (100 mg∙L –1 ) within 50 min and showed an excellent adsorption capacity of 342.06 mg∙g –1 . The presence of abundant sulfur defects in 1T/2H-MG composite could provide more adsorption and reduction active sites, which was the main reason for the enhanced removal efficiency of 1T/2H-MG in comparison with pure MoS 2 and g-C 3 N 4 . This work not only contributes an excellent adsorbent for the wastewater treatment, but also provides evidences for the defects engineering.
Constructing a 0D/3D p–n heterojunction is a feasible strategy for accelerating photo-induced charge separation and promoting photocatalytic H2 production. In this study, a 0D/3D MoS2/g-C3N4 (0D/3D-MCN) photocatalyst with a p–n heterojunction was prepared via a facile light-assisted deposition procedure, and the 3D spongy-like g-C3N4 (3D-CN) was synthesized through simple thermolysis of NH4Cl and melamine mixture. For comparison, 2D-MoS2 nanosheets were also embedded in 3D-CN by a solution impregnation method to synthesize a 2D/3D-MCN photocatalyst. As a result, the as-prepared 0D/3D-MCN-3.5% composite containing 3.5 wt% 0D-MoS2 QDs exhibited the highest photocatalytic H2 evolution rate of 817.1 μmol h−1 g−1, which was 1.9 and 19.4 times higher than that of 2D/3D-MCN-5% (containing 5 wt% 2D-MoS2 nanosheets) and 3D-CN, respectively. The results of XPS and electrochemical tests confirmed that a p–n heterojunction was formed in the 0D/3D-MCN-3.5% composite, which could accelerate the electron and hole movement in the opposite direction and retard their recombination; however, it was not found in 2D/3D-MCN-5%. This study revealed the relationship among the morphologies of MoS2 using g-C3N4 as a substrate, the formation of a p–n heterojunction, and the H2 evolution activity; and provided further insights into fabricating a 3D g-C3N4-based photocatalyst with a p–n heterojunction for photocatalytic H2 evolution.
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