Simultaneous Dual-Functional Photocatalysis by g-C3N4-Based Nanostructures

Advances in Carbon Nitride-Based Materials and Their Electrocatalytic Applications

A suitable electronic structure and efficient charge separation are significant for the performance of photocatalytic water splitting. Herein, we have designed a two-dimensional GeI2/C2N van der Waal (vdW) heterostructure and...

Enhancing the photocatalytic hydrogen generation performance and strain regulation of the vertical GeI2/C2N van der Waals heterostructure: Insights from first-principles study

In this study, manganese sesquioxide (Mn2O3) nanoparticles (NPs) were inserted into porous silica (pSiO2) and thus a mosaic-like porous composite of Mn2O3/pSiO2 was constructed by a bio-templating route. Structure and morphology analyses reveal the successful assembly and high dispersion of Mn2O3 NPs on the matrix of porous SiO2. Because of the presence of a porous structure and high number of accessible active sites, the resulting Mn2O3/pSiO2 exhibits both large adsorption capacity and remarkable catalytic activity for the removal of tetracycline (TC, 80 mg·L–1) from aqueous solutions. With the assistance of H2O2, Mn2O3/pSiO2 could synergistically degrade TC with a total removal efficiency (RE) of 80%, which is much greater than those of pSiO2 (13%) and nMn2O3 (63%). Meanwhile, Mn2O3/pSiO2 possesses a wide pH application range (3.0–11.0, RE > 83%), quite good efficiency (64%) for highly concentrated TC (240 mg·L–1), and excellent reusability (RE = 70% after four cycles). Radical-trapping tests and electrochemical measurements reveal that a direct electron transfer pathway plays the dominant role in this TC–Mn2O3/pSiO2–H2O2 catalytic system. This study provides a convenient and effective strategy to design porous composite adsorbents/catalysts for the remediation of antibiotic wastewater. 

Porous Mn2O3/pSiO2 Nanocomposites on Bio-scaffolds for Tetracycline Degradation

The applications of MOFs related materials in photo/electrochemical decontamination: An updated review

Van der Waals (vdW) heterostructures of two-dimensional monolayers are a relatively new class of materials with highly tunable band alignment, bandgap energy, and bandgap transition type. In this study, we performed density functional theory calculations to investigate how a vdW heterostructure of heptazine-based graphitic carbon nitride (hg-C3N4) and graphitic zinc oxide (g-ZnO) monolayers is formed (hg-C3N4/g-ZnO). This heterostructure is a potential solar-driven photocatalyst for the water-splitting reaction. Upon the formation of the heterostructure, a type-I indirect bandgap (Eg = 2.08 eV) is created with appropriate conduction band minimum and valence band maximum levels relative to the oxidation/reduction potentials for the water-splitting reaction. In addition, a very large electrostatic potential difference of 11.18 eV is generated across the heterostructure, leading to a large, naturally-formed, built-in electric field directing from hg-C3N4 to g-ZnO. The produced electric field forces photogenerated electrons in g-ZnO to transfer toward hg-C3N4, leading to a decrease in the electron–hole recombination rate. We also found that both g-ZnO and hg-C3N4 synergistically lead to higher light absorption of the heterostructure (λmax = 387 nm). Furthermore, band alignment, bandgap energy, and transition type of the heterostructure can be tuned by applying external perpendicular electric fields and biaxial strains. It was found that a strain of +2% leads to a Z-scheme band alignment (Eg = 2.34 eV, direct) and an electric field of 1 V A−1 leads to a type-II heterostructure (Eg = 2.29 eV, indirect), which are both beneficial for efficient water-splitting photocatalysis.

Band alignment tuning of heptazine-g-C3N4/g-ZnO vdW heterostructure as a promising water-splitting photocatalyst

Metal-organic frameworks (MOFs) are a new class of porous crystalline materials being used as photocatalysts for efficient pollutant removal and environmental remediation. In this study, the TMU-32 MOF was synthesized as an effective photocatalyst for the photodegradation of tetracycline (TC) with 96% efficiency in 60 min under visible light. The high photocatalytic activity of the TMU-32 MOF is mainly due to its large specific surface area, which is beneficial for promoting both the adsorption of TC and the separation of the photoinduced charges. Moreover, its desired crystallinity makes it a semiconductor with an appropriate band gap energy. Next, a composite of the TMU-32 MOF with Fe3O4 nanoparticles (as Fe3O4@TMU-32) was prepared as a magnetically recyclable photocatalyst. The results showed that the photocatalytic activity of the Fe3O4@TMU-32 nanocomposite is slightly lower (68% degradation of TC within 60 min) than that of TMU-32 toward TC degradation since Fe3O4 nanoparticles are not acting as a photocatalyst and are used only to make the host photocatalyst (here, TMU-32) magnetically separable. The effects of the photocatalyst concentration and recyclability on the photodegradation of TC were studied under similar conditions. We found that the Fe3O4@TMU-32 composite is easily recycled without a significant loss of photocatalytic activity after being used several times, indicating the stability of the photocatalyst. Finally, a density functional theory study was also conducted to investigate the structural and electronic properties such as the band gap energy and density of states of the TMU-32 MOF and the Fe3O4@TMU-32 composite. Our computational results are in good agreement with the experimental ones. A photocatalytic degradation mechanism was finally proposed under visible-light photoirradiation.

Kourosh Rahimi

Papers

Band alignment tuning of heptazine-g-C3N4/g-ZnO vdW heterostructure as a promising water-splitting photocatalyst

Magnetically Recyclable Fe3O4@TMU-32 Metal-Organic Framework Photocatalyst for Tetracycline Degradation Under Visible Light.