The simultaneous promotion of Cr (VI) photoreduction and tetracycline removal over 3D/2D Cu2O/BiOBr S-scheme nanostructures

A Tight-Connection g-C3N4/BiOBr (001) S-Scheme Heterojunction Photocatalyst for Boosting Photocatalytic Degradation of Organic Pollutants

The efficient separation of photogenerated charge carriers and strong oxidizing properties can improve photocatalytic performance. Here, we combine the construction of a tightly connected S-scheme heterojunction with the exposure of an active crystal plane to prepare g-C3N4/BiOBr for the degradation of high-concentration organic pollutants. This strategy effectively improves the separation efficiency of photogenerated carriers and the number of active sites. Notably, the synthesized g-C3N4/BiOBr displays excellent photocatalytic degradation activity towards various organic pollutants, including methylene blue (MB, 90.8%), congo red (CR, 99.2%), and tetracycline (TC, 89%). Furthermore, the photocatalytic degradation performance of g-C3N4/BiOBr for MB maintains 80% efficiency under natural water quality (tap water, lake water, river water), and a wide pH range (pH = 4-10). Its excellent photocatalytic activity is attributed to the tight connection between g-C3N4 and BiOBr in the S-scheme heterojunction interface, as well as the exposure of highly active (001) crystal planes. These improve the efficiency of the separation of photogenerated carriers, and maintain their strong oxidation capability. This work presents a simple approach to improving the separation of electrons and holes by tightly combining two components within a heterojunction.

2D/2D MgO/g-C3N4 S-scheme heterogeneous tight with Mg-N bonds for efficient photo-Fenton degradation: Enhancing both oxygen vacancy and charge migration

Construction of S-scheme heterojunction is an efficient strategy to enhance photocatalytic efficiency. Besides the retained redox ability, the wide work function gap and intimate interface contact are essential for efficient degradation. Nontoxic magnesium oxide (MgO) with two dimensional (2D) structures and high work function is a potential material for S-scheme photocatalysts. Herein, MgO was used to in-situ grown on graphitic carbon nitride (g-C3N4) for constructing the strongly connected MgO/g-C3N4 S-scheme photocatalyst with tight Mg-N bonds. Meanwhile, the presence of Mg-N bonds induces the formation of oxygen vacancy in MgO, which enhances the Fenton-like degradation. Furthermore, the Mg-N bond promotes the charge migration between MgO and g-C3N4. Consisting of the enhanced Fenton-like process and photocatalysis, the MgO/g-C3N4 shows a higher photo-Fenton degradation activity (80.01%) for degradation of organic pollutants (Rhodamine B, 100 mg L-1) in water, than g-C3N4 (28.46%) and MgO (55.64%). Therefore, the interfacial chemical bonds in heterojunction photocatalysts provide an efficient strategy for further enhancing the photocatalysis of S-scheme photocatalysts.

Comprehensive Insights into the Family of Atomically Thin 2D-Materials for Diverse Photocatalytic Applications

2D materials with their fascinating physiochemical, structural, and electronic properties have attracted researchers and have been used for a variety of applications such as electrocatalysis, photocatalysis, energy storage, magnetoresistance, and sensing. In recent times, 2D materials have gained great momentum in the spectrum of photocatalytic applications such as pollutant degradation, water splitting, CO2 reduction, NH3 production, microbial disinfection, and heavy metal reduction, thanks to their superior properties including visible light responsive band gap, improved charge separation and electron mobility, suppressed charge recombination and high surface reactive sites, and thus enhance the photocatalytic properties rationally as compared to 3D and other low-dimensional materials. In this context, this review spot-lights the family of various 2D materials, their properties and their 2D structure-induced photocatalytic mechanisms while giving an overview on their synthesis methods along with a detailed discussion on their diverse photocatalytic applications. Furthermore, the challenges and the future opportunities are also presented related to the future developments and advancements of 2D materials for the large-scale real-time photocatalytic applications.

CuO/NaNbO3 nanorod piezoelectric photocatalysts promoted tetracycline removal: a dynamic internal electric field

The piezoelectric electric field inside CuO/NaNbO3 nanorods promoted the separation of photoinduced carriers and inhibited being saturated by free carriers.

Hierarchical S-Scheme Heterostructure of CdIn2S4@UiO-66-NH2 toward Synchronously Boosting Photocatalytic Removal of Cr(VI) and Tetracycline

Developing highly efficient photocatalysts toward synchronously removing heavy metals and organic pollutants is still a serious challenge. Herein, we depict hierarchical S-scheme heterostructured photocatalysts prepared via in situ anchoring UiO-66-NH₂ nanoparticles onto the CdIn₂S₄ porous microsphere structures assembled with numerous nanosheets. In the mixed system of Cr(VI) and tetracycline (TC), the optimal photocatalyst (CIS@U66N-30) shows remarkable photocatalytic activities toward the synchronous removal of Cr(VI) (97.26%) and TC (close to 100% of) under visible-light irradiation for 60 min, being the best removal rates among those of the reported photocatalysts, and sustains the outstanding stability and reusability. Its reaction rate constants of Cr(VI) reduction and TC degradation are about 2.06 and 1.58 folds that in the single Cr(VI) and TC systems, respectively. The enhanced photocatalytic activities of CIS@U66N-30 mainly result from the following synergism: (1) its hierarchical structure offers abundant active sites, and the S-scheme migration mechanism of charge carriers in the heterostructure accelerates the separation and migration of the useful photoinduced electrons and holes with the high redox capability; (2) Cr(VI) and TC can serve as the electron scavenger for TC oxidation degradation and the hole and ^•OH scavenger for Cr(VI) reduction, respectively, further enhancing the separation and utilization efficiency of photoinduced electrons and holes. Besides, the possible TC degradation pathway and plausible S-scheme photocatalytic mechanism over CIS@U66N-30 for the concurrent elimination of Cr(VI) and TC are proposed.

In-situ constructed 2D/2D ZnIn2S4/Bi4Ti3O12 S-scheme heterojunction for degradation of tetracycline: Performance and mechanism insights

Semiconductor materials dominated photocatalytic technology is one of the most efficient approaches to degrade organic pollutants. However, the limited light absorption range and rapid recombination of photogenerated carriers greatly restrict the application of photocatalysts. Rational design of photocatalysts to achieve high catalytic activity and stability is of great importance. Herein, ZnIn₂S₄/Bi₄Ti₃O₁₂ S-scheme heterojunction is synthesized by growing the ZnIn₂S₄ nanosheets on the sheet-like Bi₄Ti₃O₁₂ surface via a low-temperature solvothermal method. The TC removal efficiency of optimized heterojunction reaches 82.1% within 60 min under visible light, and the rate constant is nearly 6.8 times than that of pristine ZnIn₂S₄. The favorable photocatalytic performance of heterojunction is attributed to the tight contact interface and efficient separation of photogenerated carriers. Besides, the difference in work function between ZnIn₂S₄ and Bi₄Ti₃O₁₂ leads to band bending and the establishment of built-in electric field on the contact interface of heterojunction, which facilitates the migration and separation of photogenerated carriers. Furthermore, the cycling test demonstrates the attractive stability of heterojunction. The possible TC photodegradation pathways and toxicity assessment of the intermediates are also analyzed. In conclusion, this work provides an effective strategy to prepare S-scheme heterojunction photocatalysts with favorable photocatalytic activity, which can enhance wastewater purification efficiency.

Step-doped disulfide vacancies and functional groups synergistically enhance photocatalytic activity of S-scheme Cu3SnS4/L-BiOBr towards ciprofloxacin degradation

Development of efficient photocatalysts for efficient recalcitrant organic pollutants degradation is of great significance. Herein, the step-doped disulfide vacancies S-scheme Cu₃SnS₄/L-BiOBr (CTS/L-BiOBr) heterojunction photocatalyst was prepared for ciprofloxacin (CIP) degradation. X-ray photoelectron spectroscopy (XPS) analysis, ultraviolet photo-electron spectroscopy (UPS) analysis, band structure and dominant radicals' identification together verified that the transfer of photogenerated carriers conformed to the S-scheme mechanism. Benefited from the interfacial electric field (IEF) of the S-scheme heterojunction and incorporation of L-cysteine with introducing S-vacancies and surface functional groups (-NH₂, -COO^-), photogenerated charges generation and separation of the CTS/L-BiOBr₍₁₀₎ were greatly improved. With ·OH and h⁺ as dominant reactive species, CIP removal reached 93% using CTS/L-BiOBr₍₁₀₎ within 180 min of visible light irradiation, which was 3.5 times and 2.6 times of pristine Cu₃SnS₄ and L-BiOBr, respectively. Moreover, possible CIP degradation pathways were proposed and the degradation intermediates ecotoxicity were evaluated. This study could provide reference for designing efficient S-scheme photocatalysts for recalcitrant wastewater treatment.

Construction of a Bi2MoO6/CoOx/Au system with a dual-channel charge transfer path for enhanced tetracycline degradation

The introduction of two cocatalysts CoOx and Au constructs dual carrier transfer channels, which improves the photogenerated electron–hole pairs separation efficiency and photocatalytic performance.