Interface engineered cascade-type electronic structure of 2D/0D/2D CdS-CdCO3/SnO2 quantum dots/g-C3N4 nanocomposite for boosting solar-driven photocatalysis

A rational design of heterojunctions with high-quality contacts is essential for efficiently separating photogenerated charge carries and boosting the solar-driven harvesting capability. Herein, we fabricated a novel heterojunction of SnO2 quantum dots-anchored CdS-CdCO3 with g-C3N4 nanosheets as a superior photocatalyst. SnO2 quantum dots (SQDs) with positively charged surfaces were tightly anchored on the negatively charged surface of CdS nanosheets (NSs). The resulting CdS@SnO2 was finally decorated with g-C3N4 NSs, and a new crystalline phase of CdS-CdCO3 was formed during the hydrothermal decoration process, g-C3N4 decorated CdS-CdCO3@SnO2 (CdS-CdCO3@SnO2@g-C3N4). The as-synthesized photocatalysts were evaluated for the degradation of methyl orange dye under solar light conditions. The CdS-CdCO3@SnO2@g-C3N4 exhibited 7.7-fold and 2.3-fold enhancements in photocatalytic activities in comparison to those of the bare CdS and CdS@SnO2 NSs, respectively. The optimal performance of CdS-CdCO3@SnO2@g-C3N4 is primarily attributed to the cascade-type conduction band alignments between 2D/0D/2D heterojunctions, which can harvest maximum solar light and effectively separate photoexcited charge carriers. This work provides a new inspiration for the rational design of 2D/0D/2D heterojunction photocatalyst for green energy generation and environmental remediation applications.

Rich Sulfur Vacancies and Reduced Schottky Barrier Height Synergistically Enable Au/ZnIn2S4 with Enhanced Photocatalytic CO2 Reduction into CO

Constructing the plasmonic metal/semiconductor heterostructure with a suitable Schottky barrier height (SBH) and the sufficiently reliable active sites is of importance to achieve highly efficient and selective photocatalytic CO2 reduction into hydrocarbon fuels. Herein, we report Au/sulfur vacancy-rich ZnIn2S4 (Au/VSR-ZIS) hierarchical photocatalysts, fabricated via in situ photodepositing Au nanoparticles (NPs) onto the nanosheet self-assembled ZnIn2S4 (ZIS) micrometer flowers (MFs) with rich sulfur vacancies (VS). Density functional theory (DFT) calculations confirm that for the Au/VSR-ZIS system, the Au NPs serve as the reaction sites for H2O oxidation, and the VSR-ZIS MFs serve as those for CO2 reduction. The rich VS in the Au/VSR-ZIS hybrid can reduce its SBH so as to boost more hot electrons in the Au NPs across its Schottky barrier and then inject into the conduction band (CB) of the VSR-ZIS MFs. In addition, VS can also act as the electron sink to trap the photogenerated electrons, retarding the recombination of photogenerated carriers. The two merits effectively enhance the photogenerated electron density in the surface of VSR-ZIS MFs, availing CO2 photoreduction. In addition, the introduction of rich VS in the Au/VSR-ZIS hybrid can offer more active sites, benefiting the CO2 adsorption and accelerating the desorption of CO* from the surface of the photocatalyst. Therefore, under visible light illumination with no sacrificial reagent, the optimum photocatalyst (Au/VSR-ZIS-0.4) presents the enhanced and selective CO2 photoreduction into CO (8.15 μmol g-1h-1 and near 100%), which are superior to those of most of ZIS-based and plasmon-based photocatalysts. The photocatalytic activity is about 40.0-fold as high as that of the Vs-poor-ZIS (VSP-ZIS) MFs. This work contributes a viable strategy for designing highly efficient plasmonic photocatalysts by using the synergism of the anion vacancies and the optimized SBH induced by them.

In-situ construct CuInS2/Bi/Bi2MoO6 S-scheme/Schottky dual heterojunctions catalyst for enhanced photocatalytic degradation of diclofenac sodium

In this paper, the S-scheme/Schottky heterojunction photocatalyst (CuInS2/Bi/Bi2MoO6, CIS/Bi/BMO) was successfully constructed via a facile in-situ solvothermal method, aimed at enhancing its photocatalytic performance. The results of the study on the photocatalytic degradation of diclofenac sodium (DCF) under simulated solar light irradiation revealed that the as-prepared composite exhibited remarkable catalytic efficiency in comparison to the pristine Bi2MoO6 and CuInS2. The plasmonic bismuth (Bi) was formed during the solvothermal process. Subsequently, CuInS2 and Bi were grown on the surface of Bi2MoO6 leading to forming CIS/BMO S-scheme heterojunction, along with a Schottky junction between Bi and Bi2MoO6. The use of ethylene glycol as a support was the main reason for the significant improvement in photocatalytic efficiency in the degradation of DCF. Moreover, the probable photocatalytic mechanisms for the degradation of DCF had been proposed based on the active species quenching experiments. The eleven degradation products were detected by HPLC-MS, and the degradation reaction pathway of DCF was deduced. Additionally, the CIS/Bi/BMO photocatalyst exhibited a consistently high removal rate after four cycles. This study proposes a new strategy for designing efficient S-scheme/Schottky heterojunction photocatalysts for solar energy conversion.

Simultaneous Photocatalytic Tetracycline Oxidation and Cr(VI) Reduction by Z-Scheme Multiple Layer TiO2/SnIn4S8

Wastewater pollutants are a major threat to natural resources, with antibiotics and heavy metals being common water contaminants. By harnessing clean, renewable solar energy, photocatalysis facilitates the synergistic removal of heavy metals and antibiotics. In this paper, MXene was both a template and raw material, and MXene-derived oxide (TiO2) and SnIn4S8 Z-scheme composite materials were synthesized and characterized. The synergistic mode of photocatalytic reduction and oxidation leads to the enhanced utilization of e-/h+ pairs. The TiO2/SnIn4S8 exhibited a higher photocatalytic capacity for the simultaneous removal of tetracycline (TC) (20 mg·L-1) and Cr(VI) (15 mg·L-1). The main active substances of TC degradation and Cr(VI) reduction were identified via free radical scavengers and electron paramagnetic resonance (EPR). Additionally, the potential photocatalytic degradation route of TC was thoroughly elucidated through liquid chromatography-mass spectrometry (LC-MS).

Interface Engineering in 2D/2D Heterogeneous Photocatalysts

Assembling different 2D nanomaterials into heterostructures with strong interfacial interactions presents a promising approach for novel artificial photocatalytic materials. Chemically implementing the 2D nanomaterials' construction/stacking modes to regulate different interfaces can extend their functionalities and achieve good performance. Herein, based on different fundamental principles and photochemical processes, multiple construction modes (e.g., face-to-face, edge-to-face, interface-to-face, edge-to-edge) are overviewed systematically with emphasis on the relationships between their interfacial characteristics (e.g., point, linear, planar), synthetic strategies (e.g., in situ growth, ex situ assembly), and enhanced applications to achieve precise regulation. Meanwhile, recent efforts for enhancing photocatalytic performances of 2D/2D heterostructures are summarized from the critical factors of enhancing visible light absorption, accelerating charge transfer/separation, and introducing novel active sites. Notably, the crucial roles of surface defects, cocatalysts, and surface modification for photocatalytic performance optimization of 2D/2D heterostructures are also discussed based on the synergistic effect of optimization engineering and heterogeneous interfaces. Finally, perspectives and challenges are proposed to emphasize future opportunities for expanding 2D/2D heterostructures for photocatalysis.

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.

Construction of a hierarchical ZnIn2S4/C3N4 heterojunction for the enhanced photocatalytic degradation of tetracycline

Efficient charge separation and sufficiently exposed active sites are both critical limiting factors for solar-driven organic contaminant degradation. Herein, we describe a hierarchical heterojunction photocatalyst fabricated by the in situ growth of ZnIn₂S₄ nanosheets on micro-tubular C₃N₄ (denoted as ZIS/TCN). This ZIS/TCN heterojunction photocatalyst can take advantage of the hollow structure with stronger light absorption capacity and more active sites, and its heterostructure can accelerate the separation and transfer of photogenerated charge carriers. The optimized ZIS/TCN-3 exhibits superb photocatalytic efficiency for the degradation of tetracycline (86.1%, 60 min), maintains excellent stability and recyclability, and provides a facile strategy for the synthesis of efficient heterojuction photocatalysts towards wastewater treatment. In addition, the plausible photocatalytic degradation pathway of tetracycline is proposed according to the intermediates identified by LC-mass analysis.

Anchoring ZnIn2S4 nanosheets on ZSM-5 for boosting photocatalytic Cr(vi) reduction

ZSM-5@ZnIn2S4 is constructed for highly efficient photocatalytic Cr(vi) reduction.

ZnIn2 S4 -Based Photocatalysts for Energy and Environmental Applications

As a fascinating visible-light-responsive photocatalyst, zinc indium sulfide (ZnIn₂ S₄ ) has attracted extensive interdisciplinary interest and is expected to become a new research hotspot in the near future, due to its nontoxicity, suitable band gap, high physicochemical stability and durability, ease of synthesis, and appealing catalytic activity. This review provides an overview on the recent advances in ZnIn₂ S₄ -based photocatalysts. First, the crystal structures and band structures of ZnIn₂ S₄ are briefly introduced. Then, various modulation strategies of ZnIn₂ S₄ are outlined for better photocatalytic performance, which includes morphology and structure engineering, vacancy engineering, doping engineering, hydrogenation engineering, and the construction of ZnIn₂ S₄ -based composites. Thereafter, the potential applications in the energy and environmental area of ZnIn₂ S₄ -based photocatalysts are summarized. Finally, some personal perspectives about the promises and prospects of this emerging material are provided.

Simple fabrication of Z-scheme MgIn2S4/Bi2WO6 hierarchical heterostructures for enhancing photocatalytic reduction of Cr(vi)

Direct Z-scheme MgIn2S4/Bi2WO6 hierarchical heterostructures were simply fabricated, exhibiting distinctly enhanced photocatalytic activity for Cr(vi) reduction under simulated sunlight irradiation.

Direct Z-scheme hierarchical heterostructures of oxygen-doped g-C3N4/In2S3 with efficient photocatalytic Cr(vi) reduction activity

Direct Z-scheme hierarchical heterostructures of O-doped g-C3N4/In2S3 were simply prepared, exhibiting efficient photocatalytic Cr(vi) reduction under visible light illumination.