Modulation of interfacial charge dynamics of semiconductor heterostructures for advanced photocatalytic applications

A synergistic heterojunction of SnS2/SnSSe nanosheets on GaN for advanced self-powered photodetectors

Tin-based TMDCs are gaining traction in optoelectronics due to their eco-friendliness and easy synthesis, contrasting Mo/W-based counterparts. This study pioneers the solvothermal synthesis of highly crystalline SnSSe alloy, akin to Janus structures, bridging a notable research gap. By integrating SnS2/SnSSe materials onto a GaN platform, a synergistic heterojunction is created, enhancing light absorption and the electron-hole pair separation efficiency, demonstrating a self-powered photodetection. The GaN/SnS2/SnSSe heterojunction showcases a staircase-like (type-II) band alignment and exceptional performance metrics: high photoresponsivity of 314.96 A W-1, specific detectivity of 2.0 × 1014 jones, and external quantum efficiency of 10.7 × 104% under 365 nm illumination at 150 nW cm-2 intensity and 3 V bias. Notably, the device displays intensity-dependent photocurrent and photoswitching behaviors without external bias, highlighting its unique self-powered attributes. This study underscores SnS2's significance in optoelectronics and explores SnSSe integration into van der Waals heterostructures, promising advanced photodetection devices and bias-free optoelectronics.

Sub-Nanometer Mono-Layered Metal-Organic Frameworks Nanosheets for Simulated Flue Gas Photoreduction

The dilemma between the thickness and accessible active site triggers the design of porous crystalline materials with mono-layered structure for advanced photo-catalysis applications. Here, a kind of sub-nanometer mono-layered nanosheets (Co-MOF MNSs) through the exfoliation of specifically designed Co3 cluster-based metal-organic frameworks (MOFs) is reported. The sub-nanometer thickness and inherent light-sensitivity endow Co-MOF MNSs with fully exposed Janus Co3 sites that can selectively photo-reduce CO2 into formic acid under simulated flue gas. Notably, the production efficiency of formic acid by Co-MOF MNSs (0.85 mmol g-1 h-1) is ≈13 times higher than that of the bulk counterpart (0.065 mmol g-1 h-1) under a simulated flue gas atmosphere, which is the highest in reported works up to date. Theoretical calculations prove that the exposed Janus Co3 sites with simultaneously available sites possess higher activity when compared with single Co site, validating the importance of mono-layered nanosheet morphology. These results may facilitate the development of functional nanosheet materials for CO2 photo-reduction in potential flue gas treatment.

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.

Nuclear Quantum Effects Accelerate Charge Separation and Recombination in g-C3N4/TiO2 Heterojunctions

We combined ring-polymer molecular dynamics (MD) and ab initio MD with nonadiabatic MD to study the effects of nuclear quantum effects (NQEs) on interlayer electron transfer and electron-hole recombination at the g-C3N4/TiO2 interface. Our simulations indicate that NQEs significantly affect electron transfer and electron-hole recombination dynamics, accelerating both processes. NQEs deform the g-C3N4 layer and expedite the movement of carbon and nitrogen atoms, thus, enhancing charge delocalization and interlayer coupling. This improved overlap between electronic state wave functions enhances nonadiabatic couplings, facilitating electron transfer and recombination. In addition to the enhanced nonadiabatic couplings accelerating electron transfer, the presence of NQEs narrows the energy gap and delays decoherence by mitigating overall fluctuations, because of restricted TiO2 movements overwhelming enhanced g-C3N4 fluctuations, thereby making the recombination faster. This work provides valuable insights into NQEs in light-element systems and contributes to guiding the development of highly efficient photocatalysts.

Visible Light Enhancement of Biocarbon Quantum-Dot-Decorated TiO2 for Naphthalene Removal

In this study, carbon-quantum-dot (CQD)-decorated TiO2 was prepared using an ultrasonic doping method and applied in the photocatalytic degradation of naphthalene under sunlight irradiation. The CQDs were synthesized from a typical macroalgae via diluted sulfuric acid pretreatment and hydrothermal synthesis using an optimal design, i.e., 3 wt% and 200 °C, respectively. The CQD/TiO2 composite remarkably enhanced the photocatalytic activity. The degradation of naphthalene under a visible light environment indicated that there is a synergistic mechanism between the CQDs and TiO2, in which the generation of reactive oxygen species is significantly triggered; in addition, the N that originated from the macroalgae accelerated the photocatalytic efficiency. Kinetic analysis showed that the photocatalytic behavior of the CQD/TiO2 composite followed a pseudo-first-order equation. Consequently, our combined experimental approach not only provides a facile pretreatment process for bio-CQDs synthesis, but also delivers a suitable TiO2 photocatalyst for the visible environment along with critical insights into the development of harmful macroalgae resources.

Enhanced Photocatalytic Activity of V2C MXene-Coupled ZnO Porous Nanosheets with Increased Surface Area and Effective Charge Transfer

Photocatalysis performs excellently when degrading organic pollutants, but the photocatalytic degradation rate is not high for most photocatalysts due to their narrow sunlight adsorption range and high recombination rate of electron hole pairs. Herein, we use V2C-MXene with a wide sunlight adsorption range to couple ZnO porous nanosheets and form ZnO/MXene hybrids using a facile electrostatic self-assembly method. The ZnO/MXene hybrids acquired demonstrated improved photochemical efficiency in breaking down methylene blue (MB) when contrasted with porous ZnO nanosheets. The degradation rate of MB reached 99.8% under UV irradiation for 120 min after the ZnO/MXene hybrid formation, while 38.6% was attained by the ZnO porous nanosheets. Moreover, photodegradation rate constants (k) were calculated as 3.05 × 10-3 and 5.42 × 10-2 min-1 for ZnO porous nanosheets and ZnO/MXene hybrids, respectively, indicating that the photodegradation performance was enhanced by 17.8 times after the modification of V2C. This was probably because the modification of V2C can increase the specific surface area to provide more sites for MB adsorption, widen the sunlight adsorption range to produce good photothermal effect, and facilitate the transfer of photogenerated carriers in ZnO to promote the reaction of more photogenerated carriers with MB. Hence, this work offers a simple approach to creating effective photocatalysts for breaking down organic contaminants.

Enhancing Photocatalytic Activities for Sustainable Hydrogen Evolution on Structurally Matched CuInS2/ZnIn2S4 Heterojunctions

Effective charge separation and migration pose a critical challenge in the field of solar-driven hydrogen production. In this work, a Z-scheme structured CuInS2/ZnIn2S4 heterojunction was successfully fabricated through a two-step hydrothermal synthesis method to significantly enhance the efficiency of solar-to-hydrogen energy conversion. Structural characterization revealed that the lattice-matched CuInS2/ZnIn2S4 heterojunction exhibits an enlarged interfacial contact area, which facilitates the transfer and separation of photogenerated charges. Microscopic analysis indicated that the CuInS2/ZnIn2S4 composite material has a tightly interwoven interface and a morphology resembling small sugar cubes. Photoelectrochemical spectroscopy analysis demonstrated that the heterojunction structure effectively enhances visible light absorption and charge separation efficiency, leading to an improvement in photocatalytic activity. Hydrogen production experimental data indicated that the CuInS2/ZnIn2S4 heterojunction photocatalyst prepared with a CuInS2 content of 20 wt% exhibits the highest hydrogen evolution rate, reaching 284.9 μmol·g-1·h-1. Moreover, this photocatalyst maintains robust photocatalytic stability even after three consecutive usage cycles. This study demonstrated that the Z-scheme CuInS2/ZnIn2S4 heterojunction photocatalyst exhibits enhanced hydrogen evolution efficiency, offering an effective structural design for harnessing solar energy to obtain hydrogen fuel. Therefore, this heterojunction photocatalyst is a promising candidate for practical applications in solar hydrogen production.

CdS-Based Hydrothermal Photocatalysts for Complete Reductive Dehalogenation of a Chlorinated Propionic Acid in Water by Visible Light

Cadmium sulfide (CdS)-based photocatalysts are prepared following a hydrothermal procedure (with CdCl2 and thiourea as precursors). The HydroThermal material annealed (CdS-HTa) is crystalline with a band gap of 2.31 eV. Photoelectrochemical investigation indicates a very reducing photo-potential of -0.9 V, which is very similar to that of commercial CdS. CdS-HTa, albeit having similar reducing properties, is more active than commercial CdS in the reductive dehalogenation of 2,2-dichloropropionic acid (dalapon) to propionic acid. Spectroscopic, electro-, and photoelectrochemical investigation show that photocatalytic properties of CdS are correlated to its electronic structure. The reductive dehalogenation of dalapon has a double significance: on one hand, it represents a demanding reductive process for a photocatalyst, and on the other hand, it has a peculiar interest in water treatment because dalapon can be considered a representative molecule of persistent organic pollutants and is one of the most important disinfection by products, whose removal from the water is the final obstacle to its complete reuse. HPLC-MS investigation points out that complete disappearance of dalapon passes through 2-monochloropropionic acid and leads to propionic acid as the final product. CdS-HTa requires very mild working conditions (room temperature, atmospheric pressure, natural pH), and it is stable and recyclable without significant loss of activity.

Ni, Co-Embedded MOF-Derived N-Doped Bimetallic Porous Carbon for Adsorption-Photocatalytic Degradation of Organic Dyes and Antibiotics

An efficient protocol for photocatalytic degradation of organic dyes and antibiotics has been successfully established via MOF-derived (MOF = metal-organic framework) Ni, Co-embedded N-doped bimetallic porous carbon nanocomposites (NiCo/NC). Such a NiCo/NC nanocomposite features well-distributed structures, suitable specific surface areas, and more active sites determined by various characterization analyses. The catalyst exhibits higher photocatalytic performance and stability toward the liquid-phase degradation of methylene blue (MB) under visible light irradiation for 60 min, after the adsorption-desorption equilibrium and the thorough degradation into H2O and CO2. Radical quenching experiments further confirmed the dominant effect of electron holes h+ and superoxide radical anions ·O2- for the MB photodegradation process. NiCo/NC was also appropriate for the degradation of Rhodamine B, methyl orange, tetracycline hydrochloride, and norfloxacin. Moreover, NiCo/NC is robust, and its photocatalytic activity is basically maintained after 8 cycles. This work is expected to provide additional information for the design of MOF-derived carbon material with more excellent properties and lay the foundation for further industrial applications.

Organic Donor-Acceptor Systems for Photocatalysis

Organic semiconductor materials are considered to be promising photocatalysts due to their excellent light absorption by chromophores, easy molecular structure tuning, and solution-processable properties. In particular, donor-acceptor (D-A) type organic photocatalytic materials synthesized by introducing D and A units intra- or intermolecularly, have made great progress in photocatalytic studies. More and more studies have demonstrated that the D-A type organic photocatalytic materials combine effective carrier separation, tunable bandgap, and sensitive optoelectronic response, and are considered to be an effective strategy for enhancing light absorption, improving exciton dissociation, and optimizing carrier transport. This review provides a thorough overview of D-A strategies aimed at optimizing the photocatalytic performance of organic semiconductors. Initially, essential methods for modifying organic photocatalytic materials, such as interface engineering, crystal engineering, and interaction modulation, are briefly discussed. Subsequently, the review delves into various organic photocatalytic materials based on intramolecular and intermolecular D-A interactions, encompassing small molecules, conjugated polymers, crystalline polymers, supramolecules, and organic heterojunctions. Meanwhile, the energy band structures, exciton dynamics, and redox-active sites of D-A type organic photocatalytic materials under different bonding modes are discussed. Finally, the review highlights the advanced applications of organic photocatalystsand outlines prospective challenges and opportunities.

Manipulation of interfacial charge dynamics for metal-organic frameworks toward advanced photocatalytic applications

Compared to other known materials, metal-organic frameworks (MOFs) have the highest surface area and the lowest densities; as a result, MOFs are advantageous in numerous technological applications, especially in the area of photocatalysis. Photocatalysis shows tantalizing potential to fulfill global energy demands, reduce greenhouse effects, and resolve environmental contamination problems. To exploit highly active photocatalysts, it is important to determine the fate of photoexcited charge carriers and identify the most decisive charge transfer pathway. Methods to modulate charge dynamics and manipulate carrier behaviors may pave a new avenue for the intelligent design of MOF-based photocatalysts for widespread applications. By summarizing the recent developments in the modulation of interfacial charge dynamics for MOF-based photocatalysts, this minireview can deliver inspiring insights to help researchers harness the merits of MOFs and create versatile photocatalytic systems.

Epitaxial grown [hk1] oriented 2D/1D Bi2O2S/Sb2S3 heterostructure with significantly enhanced photoelectrochemical performance

Bismuth oxysulfide (Bi2O2S) is a layered material with high carrier mobility, excellent light absorption characteristic and good stability. However, there are few reports about the use of Bi2O2S in photoelectrochemical (PEC) water splitting. In this paper, Bi2O2S nanosheets (NSs) films were prepared on FTO substrates by one-step hydrothermal method, which broke the traditional powder state of Bi2O2S prepared. Based on the high lattice matching between antimony sulfide (Sb2S3) and bismuth sulfide (Bi2S3) obtained from the topological transformation of partial Bi2O2S, Sb2S3 nanorods (NRs) with [hk1] predominant orientation were epitaxially grown on the surface of Bi2O2S to establish a transport channel for rapid carrier migration. Titanium dioxide (TiO2) electron transport layer with oxygen vacancies was introduced into the back to capture and release electrons, further reducing the recombination rate. The photocurrent density of TiO2/Bi2O2S/Sb2S3-annealed photoelectrode at 1.23 V vs. RHE was 4.37 mA/cm2, which was 13.7 times that of monomer Bi2O2S. In addition, the TiO2/Bi2O2S/Sb2S3-annealed photoelectrode had lower charge transfer resistance and the IPCE value up to 48.22%. This study is of great significance for the application of Bi2O2S based photoelectrodes in the field of PEC water splitting.

Photocatalyst Based on Nanostructured TiO2 with Improved Photocatalytic and Antibacterial Properties

This study shows an easy way to use electrochemistry and plasma layering to make Cobalt-Blue-TiO2 nanotubes that are better at catalysing reactions. Once a titanium plate has been anodized, certain steps are taken to make oxygen vacancies appear inside the TiO2 nanostructures. To find out how the Co deposition method changed the final catalyst's properties, it was put through electrochemical tests (to find the charge transfer resistance and flat band potential) and optical tests (to find the band gap and Urbach energy). The catalysts were also described in terms of their shape, ability to stick to surfaces, and ability to inhibit bacteria. When Cobalt was electrochemically deposited to Blue-TiO2 nanotubes, a film with star-shaped structures was made that was hydrophilic and antibacterial. The band gap energy went down from 3.04 eV to 2.88 eV and the Urbach energy went up from 1.171 eV to 3.836 eV using this electrochemical deposition method. Also, photodegradation tests with artificial doxycycline (DOX) water were carried out to see how useful the study results would be in real life. These extra experiments were meant to show how the research results could be used in real life and what benefits they might have. For the bacterial tests, both gram-positive and gram-negative bacteria were used, and BT/Co-E showed the best response. Additionally, photodegradation and photoelectrodegradation experiments using artificial doxycycline (DOX) water were conducted to determine the practical relevance of the research findings. The synergistic combination of light and applied potential leads to 70% DOX degradation after 60 min of BT/Co-E irradiation.

WO3-NP-activated WS2 layered heterostructures for efficient broadband (254 nm-940 nm) photodetection

Broadband photodetection including deep UV using Si is technically challenging due to its negligible optical absorption at 254 nm and the requirement of heterogeneous integration with very high bandgap photoactive materials. However, monolithic integration of high-bandgap semiconductors on Si is not possible due to CMOS fabrication incompatibility. Comprehensive experimental studies to achieve broadband photodetection including deep UV on Si are lacking in the literature. Here for the first time we have investigated 2D/0D heterojunctions of WS2/WO3 on a Si platform both experimentally and theoretically and established the charge transfer mechanism between them. Transient photocarrier decay experiments demonstrate effective quenching of excited photocarriers generated in WO3/WS2, signifying its utility in facilitating carrier transport, which is further evidenced by charge density calculation from DFT simulation. Our designed vertically aligned p-Si/WS2/WO3 heterojunction-based photodetector exhibits an excellent photosensitivity performance with a broad spectral response ranging from deep ultraviolet (254 nm) to near infrared (940 nm) wavelengths, and it not only provides a peak responsivity of 251 A W-1 and a specific detectivity of 1.89 × 014 Jones, but also possesses a rapid response speed with a rise/fall time of 0.64/0.48 s at 365 nm with a bias of 2 volt.

Modulating Electronic Metal-Support Interactions to Boost Visible-Light-Driven Hydrolysis of Ammonia Borane: Nickel-Platinum Nanoparticles Supported on Phosphorus-Doped Titania

Ammonia borane (AB) is a promising material for chemical H2 storage owing to its high H2 density (up to 19.6 wt %). However, the development of an efficient catalyst for driving H2 evolution through AB hydrolysis remains challenging. Therefore, a visible-light-driven strategy for generating H2 through AB hydrolysis was implemented in this study using Ni-Pt nanoparticles supported on phosphorus-doped TiO2 (Ni-Pt/P-TiO2 ) as photocatalysts. Through surface engineering, P-TiO2 was prepared by phytic-acid-assisted phosphorization and then employed as an ideal support for immobilizing Ni-Pt nanoparticles via a facile co-reduction strategy. Under visible-light irradiation at 283 K, Ni40 Pt60 /P-TiO2 exhibited improved recyclability and a high turnover frequency of 967.8 molH 2 ${{_{{\rm H}{_{2}}}}}$  molPt -1  min-1 . Characterization experiments and density functional theory calculations indicated that the enhanced performance of Ni40 Pt60 /P-TiO2 originated from a combination of the Ni-Pt alloying effect, the Mott-Schottky junction at the metal-semiconductor interface, and strong metal-support interactions. These findings not only underscore the benefits of utilizing multipronged effects to construct highly active AB-hydrolyzing catalysts, but also pave a path toward designing high-performance catalysts by surface engineering to modulate the electronic metal-support interactions for other visible-light-induced reactions.

Synthesis of CeO2/ZrO2/ZnO nano alloy oxide and investigation of photocatalysis of naphthol orange under sunlight

Novel metal-like cerium- and zirconium-doped ZnO photocatalysts were prepared herein with various proportions of molar ratios via a cost-effective co-precipitation method. The effects of novel metal doping on the photocatalytic activity of ZnO were studied. Various techniques were used to investigate the structural, morphological, and elemental composition, particle size, optical properties, and catalytic activity of the synthesized photocatalysts. It was found that the crystallite size and particle size of the nano alloy oxides were 15.12 ± 1 and 5 ± 1 nm, respectively, and the surface morphology of the nanoparticles indicated a satisfactory surface area. Among all synthesized nanocomposites, Ce_xZr_xZn_xO₅ (x = 1) [CZ₁Z₂-A] exhibited satisfactory photo-oxidation activity against naphthol orange (NO) under sunlight with a rate constant of 57.5 × 10^-3 min^-1. The effects of pH, inorganic salts, dye concentrations, and catalytic dosage on NO degradation were studied. A probable mechanistic pathway for the degradation of NO in the presence of CZ₁Z₂-A was proposed, and studies of sacrificial agents indicated that superoxide radical anion (O₂˙^-) was the main accountable active species in NO degradation. In addition, CZ₁Z₂-A exhibited excellent recyclability potential, and XRD studies revealed that there was no change in the crystal structure before or after degradation, which indicated its high stability. The intriguing finding was that Ce- and Zr-doped ZnO did not exhibit satisfactory catalytic performance in the photo-oxidation of NO. However, the composite formula of Ce_xZr_xZn_xO₅ (x = 1) with a 1 : 1 : 1 ratio of metal ions offered excellent catalytic activity.

Efficient Photoelectrochemical Hydrogen Generation Using Eco-Friendly "Giant" InP/ZnSe Core/Shell Quantum Dots

InP quantum dots (QDs) are promising building blocks for use in solar technologies because of their low intrinsic toxicity, narrow bandgap, large absorption coefficient, and low-cost solution synthesis. However, the high surface trap density of InP QDs reduces their energy conversion efficiency and degrades their long-term stability. Encapsulating InP QDs into a wider bandgap shell is desirable to eliminate surface traps and improve optoelectronic properties. Here, we report the synthesis of "giant" InP/ZnSe core/shell QDs with tunable ZnSe shell thickness to investigate the effect of the shell thickness on the optoelectronic properties and the photoelectrochemical (PEC) performance for hydrogen generation. The optical results demonstrate that ZnSe shell growth (0.9-2.8 nm) facilitates the delocalization of electrons and holes into the shell region. The ZnSe shell simultaneously acts as a passivation layer to protect the surface of InP QDs and as a spatial tunneling barrier to extract photoexcited electrons and holes. Thus, engineering the ZnSe shell thickness is crucial for the photoexcited electrons and hole transfer dynamics to tune the optoelectronic properties of "giant" InP/ZnSe core/shell QDs. We obtained an outstanding photocurrent density of 6.2 mA cm^-1 for an optimal ZnSe shell thickness of 1.6 nm, which is 288% higher than the values achieved from bare InP QD-based PEC cells. Understanding the effect of shell thickness on surface passivation and carrier dynamics offers fundamental insights into the suitable design and realization of eco-friendly InP-based "giant" core/shell QDs toward improving device performance.

Efficient light-driven hydrogen evolution and azo dye degradation over the GdVO4@g-C3N4 heterostructure

A straightforward hydrothermal technique was used for the synthesis of a g-C₃N₄/GdVO₄ (CN/GdV) heterostructure as an alternate material for energy and environmental applications. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the synthesized g-C₃N₄ (CN), GdVO₄ (GdV), and the CN/GdV heterostructure. The characterization results revealed the distribution of GdV over CN sheets. The as-fabricated materials were tested for their capacity to evolve hydrogen gas and degrade two azo dyes (Amaranth; AMR and Reactive Red2; RR2) in the presence of visible light. When compared to pure CN and GdV, the efficiency of CN/GdV toward hydrogen evolution was high, with H₂ evolution of 8234, 10 838, and 16 234 μmol g^-1 in 4 h, respectively. The CN/GdV heterostructure was able to degrade 96% and 93% of AMR (60 min) and RR2 (80 min), respectively. The enhanced activity with CN/GdV could be attributed to the type-II heterostructure and decreased recombination of charge carriers. The intermediate analysis of AMR and RR2 degradation was conducted using mass spectrometry (MS). The mechanism of photocatalysis was investigated and is discussed based on the optical and electrochemical characterizations. The efficient photocatalytic characteristics of CN/GdV could promote further research on metal vanadate nanocomposite materials.

Unraveling the atomic-level vacancy modulation in Cu9S5 for NIR-driven efficient inhibition of drug-resistant bacteria: Key role of Cu vacancy position

Cu₉S₅ possesses high hole concentration and potential superior electrical conductivity as a novel p-type semiconductor, whose biological applications remain largely unexploited. Encouraged by our recent work that Cu₉S₅ has enzyme-like antibacterial activity in the absence of light, which may further enhance the near infrared (NIR) antibacterial performance. Moreover, vacancy engineering can modulate the electronic structure of the nanomaterials and thus optimize their photocatalytic antibacterial activities. Here, we designed two different atomic arrangements with same V_CuSCu vacancies of Cu₉S₅ nanomaterials (CSC-4 and CSC-3) determined by positron annihilation lifetime spectroscopy (PALS). Aiming at CSC-4 and CSC-3 as a model system, for the first time, we investigated the key role of different copper (Cu) vacancies positions in vacancy engineering toward optimizing the photocatalytic antibacterial properties of the nanomaterials. Combined with the experimental and theoretical approach, CSC-3 exhibited stronger absorption energy of surface adsorbate (LPS and H₂O), longer lifetime of photogenerated charge carriers (4.29 ns), and lower reaction active energy (0.76 eV) than those of CSC-4, leading to the generation of abundant ·OH for attaining rapid drug-resistant bacteria killed and wound healed under NIR light irradiation. This work provided a novel insight for the effective inhibition of drug-resistant bacteria infection via vacancy engineering at the atomic-level modulation.

Super-Photothermal Effect-Mediated Fast Reaction Kinetic in S-Scheme Organic/Inorganic Heterojunction Hollow Spheres Toward Optimized Photocatalytic Performance

Using full solar spectrum for energy conversion and environmental remediation is a major challenge, and solar-driven photothermal chemistry is a promising route to achieve this goal. Herein, this work reports a photothermal nano-constrained reactor based on hollow structured g-C₃ N₄ @ZnIn₂ S₄ core-shell S-scheme heterojunction, where the synergistic effect of super-photothermal effect and S-scheme heterostructure significantly improve the photocatalytic performance of g-C₃ N₄ . The formation mechanism of g-C₃ N₄ @ZnIn₂ S₄ is predicted in advance by theoretical calculations and advanced techniques, and the super-photothermal effect of g-C₃ N₄ @ZnIn₂ S₄ and its contribution to the near-field chemical reaction is confirmed by numerical simulations and infrared thermography. Consequently, the photocatalytic degradation rate of g-C₃ N₄ @ZnIn₂ S₄ for tetracycline hydrochloride is 99.3%, and the photocatalytic hydrogen production is up to 4075.65 µmol h^-1 g^-1 , which are 6.94 and 30.87 times those of pure g-C₃ N₄ , respectively. The combination of S-scheme heterojunction and thermal synergism provides a promising insight for the design of an efficient photocatalytic reaction platform.

A review of tungsten trioxide (WO3)-based materials for antibiotics removal via photocatalysis

Antibiotics are extensively used in human medicine and animal breeding. The use of antibiotics has posed significant risks and challenges to the natural water environment. On a global scale, antibiotics have been frequently detected in the environment, azithromycin (254-529 ng·L^-1), ciprofloxacin (245-1149 ng·L^-1), ofloxacin (518-1998 ng·L^-1), sulfamethoxazole (1325-5053 ng·L^-1), and tetracycline (31.4-561 ng·L^-1) are the most detected antibiotics in wastewater and surface water. Abuses of antibiotics has caused a significant threat to water resources and has seriously threatened the survival of human beings. Therefore, there is an urgent need to reduce antibiotic pollution and improve the environment. Researchers have been trying to develop effective methods and technologies for antibiotic degradation in water. Finding efficient and energy-saving methods for treating water pollutants has become an important global topic. Photocatalytic technology can effectively remove highly toxic, low-concentration, and difficult-to-treat pollutants, and tungsten trioxide (WO₃) is an extremely potential alternative catalyst. Pt/WO₃ photocatalytic degradation efficiency of tetracycline was 72.82%, While Cu-WO₃ photocatalytic degradation efficiency of tetracycline was 96.8%; WO₃/g-C₃N₄ photocatalytic degradation efficiency of ceftiofur was 70%, WO_3/W photocatalytic degradation efficiency of florfenicol was 99.7%; WO₃/CdWO₄ photocatalytic degradation efficiency of ciprofloxacin was 93.4%; WO₃/Ag photocatalytic degradation efficiency of sulfanilamide was 96.2%. Compared to other water purification methods, photocatalytic technology is non-toxic and ensures complete degradation through a stable reaction process, making it an ideal water treatment method. Here, we summarize the performance and corresponding principles of tungsten trioxide-based materials as a photocatalytic catalyst and provide substantial insight for further improving the photocatalytic potential of WO₃-based materials.

Direct Interfacial Excitation from TiO2 to Cu(II) Nanoclusters Enables Cathodic Photoresponse for Hydrogen Evolution under Visible-Light Irradiation

The titanium dioxide (TiO₂ ) photocatalyst is only active under UV irradiation due to its wide-gap nature. A novel excitation pathway denoted as interfacial charge transfer (IFCT) has been reported to activate copper(II) oxide nanoclusters-loaded TiO₂ powder (Cu(II)/TiO₂ ) under visible-light irradiation for only organic decomposition (downhill reaction) so far. Here, the photoelectrochemical study shows that the Cu(II)/TiO₂ electrode exhibits a cathodic photoresponse under visible-light and UV irradiation. It originates from H₂ evolution on the Cu(II)/TiO₂ electrode, while O₂ evolution takes place on the anodic side. Based on the concept of IFCT, a direct excitation of electrons from the valence band of TiO₂ to Cu(II) clusters initiates the reaction. This is the first demonstration of a direct interfacial excitation-induced cathodic photoresponse for water splitting without any addition of a sacrificial agent. This study is expected to contribute to the development of abundant visible-light-active photocathode materials for fuel production (uphill reaction).

Three-Channel Electron Transfer for Estimating Time Constants Correlated with Photocatalytic Photon Utilization

Although the potential barrier for semiconductor-cocatalyst interfacial electron transfer can be reduced by intensifying the irradiation, the photocatalytic reaction still suffers from a low photon utilization. We here propose a trichannel electron transfer model to demonstrate that the photogenerated oxidative intermediates deprive electrons from the photocatalyst and compete with the target reaction. This model can evaluate the time constant for each electronic process involved in the target reaction and predict photocatalytic photon utilization, which is closely related to the evolution of the oxidative intermediates.

Dislocated Bilayer MOF Enables High-Selectivity Photocatalytic Reduction of CO2 to CO

The highly selective photoreduction of CO₂ into valuable small-molecule chemical feedstocks such as CO is an effective strategy for addressing the energy crisis and environmental problems. However, it remains a challenge because the complex CO₂ photoreduction process usually generates multiple possible products and requires a subsequent separation step. In this paper, 2D monolayer and bilayer porphyrin-based metal-organic frameworks (MOFs) are successfully constructed by adjusting the reaction temperature and solvent polarity with 5,10,15,20-tetrakis(4-pyridyl)porphyrin as the light-harvesting ligand. The bilayer MOF is a low-dimensional MOF with a special structure in which the upper and lower layers are arranged in dislocation and are bridged by halogen ions. This bilayer MOF exhibits 100% ultra-high selectivity for the reduction of CO₂ to CO under simulated sunlight without any cocatalyst or photosensitizer and can be recycled at least three times. The intrinsic mechanism of this photocatalytic CO₂ reduction process is explored through experimental characterization and density functional theory (DFT) calculations. This work shows that the rational design of the number of layers in 2D MOF structures can tune the stability of these structures and opens a new avenue for the design of highly selective MOF photocatalysts.

CuO nanorod arrays by gas-phase cation exchange for efficient photoelectrochemical water splitting

CuO has been considered a promising candidate for photoelectrochemical water splitting electrodes owing to its suitable bandgap, favorable band alignments, and earth-abundant nature. In this paper, a novel gas-phase cation exchange method was developed to synthesize CuO nanorod arrays by using ZnO nanorod arrays as the template. ZnO nanorods were fully converted to CuO nanorods with aspect ratios of 10-20 at the temperature range from 350 to 600 °C. The as-synthesized CuO nanorods exhibit a photocurrent as high as 2.42 mA cm^-2 at 0 V vs. RHE (reversible hydrogen electrode) under 1.5 AM solar irradiation, demonstrating the potential as the photoelectrode for efficient photoelectrochemical water splitting. Our method provides a new approach for the rational fabrication of high-performance CuO-based nanodevices.

V. Metal peroxides as potential photocatalysts for environmental remediation

Inorganic oxide materials such as TiO₂ and ZnO have been extensively studied for environmental remediation, that operates through photo generated Reactive Oxygen Species (ROS) such as H₂O₂, ·OH and O₂ ^- to decontaminate waste water. However, inorganic solid oxidants such as metal peroxides capable of generating ROS in aqueous solutions have not been studied for environmental remediation. Towards this objective, we have synthesized peroxides of Zn, Mg, and Ba and characterized these by powder X-ray diffraction, Transmission Electron Microscopy, UV-visible spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity of these wide band gap semiconductors has also been investigated. The novelty of the work is in the use of these peroxides as chemical sources of ROS in aqueous suspensions in addition to their photochemical generation. Hence, these peroxides, in particular Ba, exhibit high photocatalytic activity, better than the well-known ZnO. The mechanisms of ROS generation and subsequent dye degradation are elucidated. ROS has been estimated and is correlated to the photocatalytic activity. This work reports for the first time BaO₂ as potential photocatalyst.

Immobilization of a TiO2-PEDOT:PSS hybrid heterojunction photocatalyst for degradation of organic effluents

Heterojunction photocatalysts have recently emerged for use in degradation of organic pollutants, typically being suspended in effluent solution to degrade it. Post degradation, the catalyst must be removed from the treated solution, which consumes both energy and time. Moreover, the separation of nano catalysts from the treated solution is challenging. In the present work, we explore fabrication of immobilized TiO₂-PEDOT:PSS hybrid heterojunction catalysts with the support of a PVA (polyvinyl alcohol) matrix. These photocatalytic films do not require any steps to separate the powdered catalyst from the treated water. While the PVA-based films are unstable in water, their stability could be significantly enhanced by heat treatment, enabling efficient removal of organic effluents like methylene blue (MB) and bisphenol-A (BPA) from the aqueous solution under simulated sunlight irradiation. Over 20 cycles, the heterojunction photocatalyst maintained high photocatalytic activity and showed excellent stability. Hence, an immobilization of the TiO₂-PEDOT:PSS hybrid heterojunction is suggested to be beneficial from the viewpoint of reproducible and recyclable materials for simple and efficient wastewater treatment.

Ligand-assisted morphology regulation of AuNi bimetallic nanocrystals for efficient hydrogen evolution

We report the controllable synthesis of AuNi core-shell (c-AuNi) and Janus (j-AuNi) nanocrystals (NCs) with uniform shape, tunable size and compositions in the presence of trioctylphosphine (TOP) or triphenylphosphine (TPP). The morphology of the AuNi bimetallic NCs could be regulated by varying the structure and concentration of phosphine ligands. The ligand-directed structural evolution mechanism of AuNi bimetallic NCs was investigated and discussed in detail. When loaded on graphitic carbon nitride (GCN) for photocatalytic hydrogen generation, the obtained j-AuNi NCs showed much higher activity for hydrogen evolution than the monometallic (Au and Ni) counterparts, owing to the synergistic effect of plasmon enhanced light absorption from the Au portion and additional electron sink effect from the Ni portion. This work provides a promising route for preparing low-cost Au-based bimetallic catalysts with controllable morphologies and high activities for hydrogen production.

Induced abundant oxygen vacancies in Sc2VO5-δ /g-C3N4 heterojunctions for enhanced photocatalytic degradation of levofloxacin

Sc₂VO_5-δ /g-C₃N₄ heterojunctions (SVCs) with abundant oxygen vacancies (OVs) were synthesized by ultrasonic exfoliation combined with the thermal etching method. The structures, OVs and spatial separation of the photogenerated carriers were systematically characterized. The results manifested that the SVCs were successfully constructed via the strong interaction between g-C₃N₄ (CN) and Sc₂VO_5-δ (SV). The SVCs possessed a higher concentration of OVs than that of pristine CN and SV. The formation of the SVC heterostructures and the optimization of the OVs were the two major factors to accelerate the separation of the charge carriers and finally to improve the photocatalysis performance. The as-prepared 10%SVC (containing 10 wt% of SV) catalyst exhibited the highest OV concentration and the best photocatalytic performance. The levofloxacin (LVX) photodegradation activity showed a positive correlation with the OV concentration. The photocatalytic degradation efficiencies were 89.1, 98.8 and 99.0% on 10%SVC for LVX, methylene blue (MB) and rhodamine B (RhB), respectively. These photodegradation processes followed the pseudo first order kinetic equation. The apparent rate constant (k _app) of LVX degradation on 10%SVC was 11.0 and 7.5 times that of CN and SV. The h⁺, ˙OH and ˙O₂ ^- were the major reactive species in the photodegradation process.

Au@Cu2O Core-Shell and Au@Cu2Se Yolk-Shell Nanocrystals as Promising Photocatalysts in Photoelectrochemical Water Splitting and Photocatalytic Hydrogen Production

In this work, we demonstrated the practical use of Au@Cu₂O core-shell and Au@Cu₂Se yolk-shell nanocrystals as photocatalysts in photoelectrochemical (PEC) water splitting and photocatalytic hydrogen (H₂) production. The samples were prepared by conducting a sequential ion-exchange reaction on a Au@Cu₂O core-shell nanocrystal template. Au@Cu₂O and Au@Cu₂Se displayed enhanced charge separation as the Au core and yolk can attract photoexcited electrons from the Cu₂O and Cu₂Se shells. The localized surface plasmon resonance (LSPR) of Au, on the other hand, can facilitate additional charge carrier generation for Cu₂O and Cu₂Se. Finite-difference time-domain simulations were carried out to explore the amplification of the localized electromagnetic field induced by the LSPR of Au. The charge transfer dynamics and band alignment of the samples were examined with time-resolved photoluminescence and ultraviolet photoelectron spectroscopy. As a result of the improved interfacial charge transfer, Au@Cu₂O and Au@Cu₂Se exhibited a substantially larger photocurrent of water reduction and higher photocatalytic activity of H₂ production than the corresponding pure counterpart samples. Incident photon-to-current efficiency measurements were conducted to evaluate the contribution of the plasmonic effect of Au to the enhanced photoactivity. Relative to Au@Cu₂O, Au@Cu₂Se was more suited for PEC water splitting and photocatalytic H₂ production by virtue of the structural advantages of yolk-shell architectures. The demonstrations from the present work may shed light on the rational design of sophisticated metal-semiconductor yolk-shell nanocrystals, especially those comprising metal selenides, for superior photocatalytic applications.

Enhancement of Plasmon-Induced Photoelectrocatalytic Water Oxidation over Au/TiO2 with Lithium Intercalation

Plasmon-induced chemical reaction is an emerging field but its development faces huge challenges because of low quantum efficiency. Herein, we report that the solar energy conversion efficiency of Au/TiO₂ in plasmon-induced water oxidation is greatly enhanced by intercalating Li⁺ into TiO₂ . An incident photon-to-current efficiency as high as 2.0 %@520 nm is achieved by Au/Li_0.2 TiO₂ in photoelectrocatalytic water oxidation, realizing a 33-fold enhancement in photocurrent density compared with Au/TiO₂ . The superior photoelectrocatalytic performance is mainly ascribed to the enhanced electric conductivity and higher catalytic activity of Li_0.2 TiO₂ . Furthermore, the ultrafast transient absorption spectroscopy suggests that lithium intercalation into TiO₂ could change the dynamics of hot electron relaxation in Au nanoparticles. This work demonstrates that intercalation of alkaline ions into semiconductors can promote the charge separation efficiency of the plasmonic effect of Au/TiO₂ .

MOF composites derived BiFeO3@Bi5O7I n-n heterojunction for enhanced photocatalytic performance

BiFeO₃is a photocatalyst with excellent performance. However, its applications are limited due to its wide bandgap. In this paper, MIL-101(Fe)@BiOI composite material is synthesized by hydrothermal method and then calcined at high temperature to obtain BiFeO₃@Bi₅O₇I composite material with high degradation capacity. Among them, an n-n heterojunction is formed, which improves the efficiency of charge transfer, and the recombination of light-generated electrons and holes promotes improved photocatalytic efficiency and stability. The result of photocatalytic degradation of tetracycline under visible light irradiation showed, BiFeO₃@Bi₅O₇I (1:2) has the best photodegradation effect, with a degradation rate of 86.4%, which proves its potential as a photocatalyst.

An Instantaneous Recombination Rate Method for the Analysis of Interband Recombination Processes in ZnO Crystals

Time-resolved photoluminescence (TRPL) analysis is often performed to assess the qualitative features of semiconductor crystals using predetermined functions (e.g., double- or multi-exponentials) to fit the decays of PL intensity. However, in many cases—including the notable case of interband PL in direct gap semiconductors—this approach just provides phenomenological parameters and not fundamental physical quantities. In the present work, we highlight that within a properly chosen range of laser excitation, the TRPL of zinc oxide (ZnO) bulk crystals can be described with excellent precision with second-order kinetics for the total recombination rate. We show that this allows us to define an original method for data analysis, based on evaluating the “instantaneous” recombination rate that drives the initial slope of the decay curves, acquired as a function of the excitation laser fluence. The method is used to fit experimental data, determining useful information on fundamental quantities that appear in the second-order recombination rate, namely the PL (unimolecular) lifetime, the bimolecular recombination coefficient, the non-radiative lifetime and the equilibrium free-carrier concentration. Results reasonably close to those typically obtained in direct gap semiconductors are extracted. The method may represent a useful tool for gaining insight into the recombination processes of a charge carrier in ZnO, and for obtaining quantitative information on ZnO excitonic dynamics.

Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review

Photocatalysis is an advanced technique that transforms solar energy into sustainable fuels and oxidizes pollutants via the aid of semiconductor photocatalysts. The main scientific and technological challenges for effective photocatalysis are the stability, robustness, and efficiency of semiconductor photocatalysts. For practical applications, researchers are trying to develop highly efficient and stable photocatalysts. Since the literature is highly scattered, it is urgent to write a critical review that summarizes the state-of-the-art progress in the design of a variety of semiconductor composite photocatalysts for energy and environmental applications. Herein, a comprehensive review is presented that summarizes an overview, history, mechanism, advantages, and challenges of semiconductor photocatalysis. Further, the recent advancements in the design of heterostructure photocatalysts including alloy quantum dots based composites, carbon based composites including carbon nanotubes, carbon quantum dots, graphitic carbon nitride, and graphene, covalent-organic frameworks based composites, metal based composites including metal carbides, metal halide perovskites, metal nitrides, metal oxides, metal phosphides, and metal sulfides, metal-organic frameworks based composites, plasmonic materials based composites and single atom based composites for CO₂ conversion, H₂ evolution, and pollutants oxidation are discussed elaborately. Finally, perspectives for further improvement in the design of composite materials for efficient photocatalysis are provided.

Spatial Separation of Photogenerated Charges on Well-Defined Bismuth Vanadate Square Nanocrystals

Crystal facet engineering has been recognized as a powerful strategy to finely modulate the charge separation behavior in semiconductor photocatalysis; however, disclosing the intrinsic roles that the morphologies and crystal facets play on photogenerated charge separation of semiconductor nanocrystals remains elusive. Herein, exemplified on the typical visible-light-responsive photocatalyst bismuth vanadate (BiVO₄ ), for the first time, the successful fabrication is reported of well-defined BiVO₄ square nanocrystals with precisely controllable (040)/(200) facet proportion, which undergo a dissolution-recrystallization-facet growth process accompanied with tetragonal to monoclinic phase transition. Spatial separation of photogenerated electrons and holes has been evidently demonstrated to take place between (040) and (200) facets of BiVO₄ nanocrystals, on which the charge separation efficiency is verified to definitely depend on the facet proportion of (040)/(200). Further theoretical simulation reveals that the matching degree of charge collection length and crystal configuration is considered to be the major factor determining charge separation efficiency of BiVO₄ nanocrystals. This study presents a strategy to fabricate morphology-tailored semiconductors, which will be favorable to advance the understanding of spatial charge separation in semiconductor photocatalysis.

Synergistic Effect of the Sulfur Vacancy and Schottky Heterojunction on Photocatalytic Uranium Immobilization: The Thermodynamics and Kinetics

Not only a critical matter in the nuclear fuel cycle but uranium is also a global contaminant with both radioactive and chemical toxicity. Reducing soluble hexavalent uranium [U(VI)] to relatively nonimmigrated tetravalent uranium [U(IV)] by photocatalytic technologies is recognized as a highly promising strategy for avoiding environmental pollution and re-extracting uranium resources from nuclear wastewater. Herein, we have designed a heterojunction photocatalyst constructed from the carbon aerogels (CA) and the CdS nanoflowers with an S-vacancy (CA@CdS-SV). With the S-vacancy and heterojunction being synergized, the U(VI) removal rate exceeded 97% in 40 min without the addition of any sacrificial agents. As impacted by the synergistic effects of the S-vacancy and heterojunction, thermodynamics and kinetics revealed that photogenerated electrons were first captured via shallow traps generated by vacancies on CdS-SV and then transferred to the CA surfaces through the heterojunction to realize the spatial separation of carriers, thereby achieving a satisfactory performance. This work is considered to underpin the improvement of U(VI) immobilization by exploiting the synergistic effect of vacancy engineering and the Schottky heterojunction from the perspective of thermodynamics and kinetics.

Enhanced photocatalytic activity of a flower-like In2O3/ZnGa2O4:Cr heterojunction composite with long persisting luminescence

Flower-like In2O3/ZnGa2O4:Cr heterojunction composites not only have high photocatalytic efficiency for rhodamine B degradation, but also have a long persisting luminescence performance.

Photoelectrochemical performance of a spin coated TiO2 protected BiVO4-Cu2O thin film tandem cell for unassisted solar water splitting

A tandem cell consisting of a Mo-BiVO₄/TiO₂/FeOOH photoanode–Cu₂O/TiO₂/MoS₂ photocathode was prepared for unassisted solar water splitting. The protective TiO₂ layer was prepared by a cost-effective spin coating technique. The individual Mo-BiVO₄/TiO₂/FeOOH photoanode and the Cu₂O/TiO₂/MoS₂ photocathode yielded a current density of ∼0.81 mA cm⁻² at 1.23 V vs. RHE and ∼−1.88 mA cm⁻² at 0 V vs. RHE, respectively under 100 mW cm⁻² xenon lamp illumination. From the individual photoelectrochemical analysis, we identify the operating points of the tandem cell as 0.66 V vs. RHE and 0.124 mA cm⁻². The positive current density from the operating points proves the possibility of non-zero operation of the tandem cell. Finally, a two-electrode Mo-BiVO₄/TiO₂/FeOOH-Cu₂O/TiO₂/MoS₂ tandem cell was constructed and analysed for unassisted operation. The obtained unassisted current density of the tandem cell was ∼65.3 μA cm⁻² with better stability compared to the bare BiVO₄-Cu₂O tandem cell. The results prove that the spin coated TiO₂ protective layer can be a viable approach to protect the photoelectrodes from photocorrosion with better stability and enhanced photoelectrochemical (PEC) performance.

Mo-BiVO₄/TiO₂/FeOOH photoanode–Cu₂O/TiO₂/MoS₂ photocathode tandem cells with photoelectrochemical stability testing.

Revealing the role of surface elementary doping in photocatalysis

Doping CdS with manganese can catalyze hole extraction and facilitate interfacial electron transfer to metallic cocatalyst. This reduces the activation energy for spatial separation of photogenerated charge carriers and enhances photon utilization.

Intriguing electronic, optical and photocatalytic performance of BSe, M2CO2 monolayers and BSe-M2CO2 (M = Ti, Zr, Hf) van der Waals heterostructures

Using density functional (DFT) theory calculations, we have investigated the electronic band structure, optical and photocatalytic response of BSe, M₂CO₂ (M = Ti, Zr, Hf) monolayers and their corresponding BSe–M₂CO₂ (M = Ti, Zr, Hf) van der Waals (vdW) heterostructures. Optimized lattice constant, bond length, band structure and bandgap values, effective mass of electrons and holes, work function and conduction and valence band edge potentials of BSe and M₂CO₂ (M = Ti, Zr, Hf) monolayers are in agreement with previously available data. Binding energies, interlayer distance and Ab initio molecular dynamic simulations (AIMD) calculations show that BSe–M₂CO₂ (M = Ti, Zr, Hf) vdW heterostructures are stable with specific stacking and demonstrate that these heterostructures might be synthesized in the laboratory. The electronic band structure shows that all the studied vdW heterostructures have indirect bandgap nature – with the CBM and VBM at the Γ–K and Γ-point of BZ for BSe–Ti₂CO₂, respectively; while for BSe–Zr₂CO₂ and BSe–Hf₂CO₂ vdW heterostructures the CBM and VBM lie at the K-point and Γ-point of BZ, respectively. Type-II band alignment in BSe–M₂CO₂ (M = Ti, Zr, Hf) vdW heterostructures prevent the recombination of electron–hole pairs, and hence are crucial for light harvesting and detection. Absorption spectra are investigated to understand the optical behavior of BSe–M₂CO₂ (M = Ti, Zr, Hf) vdW heterostructures, where the lowest energy transitions are dominated by excitons. Furthermore, BSe–M₂CO₂ (M = Ti, Zr, Hf) vdW heterostructures are found to be potential photocatalysts for water splitting at pH = 0, and exhibit enhanced optical properties in the visible light zones.

Using density functional theory calculations, we have investigated the electronic band structure, optical and photocatalytic response of BSe, M₂CO₂ (M = Ti, Zr, Hf) monolayers and their corresponding BSe–M₂CO₂ (M = Ti, Zr, Hf) van der Waals heterostructures.

Construction of CdSe-AuPd quantum dot 0D/0D hybrid photocatalysts: charge transfer dynamic study with electrochemical analysis for improved photocatalytic activity

The integration of semiconductor quantum dots and noble metal nanoparticles can efficiently couple numerous effects corresponding to the individual domains of the hybrid system for a variety of applications. Herein, we establish a direct correlation between the electronic band structure and optical band gap of monometallic and bimetallic alloy nanoparticle decorated CdSe quantum dots, which in turn regulate the charge shuttling dynamics in a quantum dot hybrid (QDH) system. Directly coupled Au, Pd, AuPd, and CdSe QDHs were prepared via a simple fabrication technique. The photoluminescence intensity of the QDHs was quenched compared to that of CdSe quantum dots with a maximumally diminished CdSe-AuPd system. Broadening of the absorbance peak along with a blue shift for QDHs confirm the interaction of the energy levels of the QDs and metal domains. AuPd decorated CdSe QDs demonstrate enhanced photocatalytic activity compared to their monometallic counterparts, which has made them interesting catalysts reported for the first time. Lifetime decay measurements, which isolated the individual charge-transfer steps, showed that a maximum amount of photoexcitons can be separated by bimetallic alloy decoration compared to monometallic ones. Cyclic voltammetry results offer insight into the change in the conduction band edge energy position for both monometallic and bimetallic incorporating semiconductor hybrid systems. Our findings reveal that photoexcited semiconductor quantum dots undergo charge equilibration when the QDs are in contact with metallic domains, influencing the shifting of the conduction band energy level of the hybrid to a more negative potential, and this is a maximum for the CdSe-AuPd hybrid, resulting in the best photocatalytic activity. Shuttling of electrons around the conduction band of CdSe and the Fermi level of the metallic domains is the main deciding factor for an efficient photocatalyst hybrid system.

Highly efficient visible light active Cu-ZnO/S-g-C3N4 nanocomposites for efficient photocatalytic degradation of organic pollutants

The photocatalytic activity of photocatalysts is severely hampered by limited visible light harvesting and unwanted fast recombination of photogenerated e^- and h⁺. In the current study, the photocatalytic efficiency of Cu-ZnO/S-g-C₃N₄ (CZS) nanocomposites was investigated against MB dye. The composite materials were designed via chemical co-precipitation method and characterised by important analytical techniques. Distinctive heterojunctions developed between S-g-C₃N₄ and Cu-ZnO in the CZS composite were revealed by TEM. The synthesized composites exhibit a huge number of active sites, a large surface area, a smaller size and better visible light absorption. The considerable enhancement in the photocatalytic activity of CZS nanocomposites might be accredited to the decay in the e-h pair recombination rate and a red shift in the visible region, as observed by PL and optical analysis, respectively. Furthermore, the metal (Cu) doping into the S-g-C₃N₄/ZnO matrix created exemplary interfaces between ZnO and S-g-C₃N₄, and maximized the photocatalytic activity of CZS nanocomposites. In particular, CZS nanocomposites synthesized by integrating 25% S-g-C₃N₄ with 4% Cu-ZnO (CZS-25 NCs) exhibited the 100% photocatalytic degradation of MB in 60 minutes under sunlight irradiation. After six cycles, the photocatalytic stability of CZS-25 NCs was excellent. Likewise, a plausible MB degradation mechanism is proposed over CZS-25 NCs based on photoluminescence and reactive species scavenger test observation. The current research supports the design of novel composites for the photocatalytic disintegration of organic contaminants.