Near-Infrared-Responsive Photocatalysts

Metal-Free C60-Doped Mesoporous Carbon Nitride Drives Red-Light Photocatalysis

The pursuit of novel strategies for synthesizing high-performance nanostructures of graphitic carbon nitride (g-C3N4) has garnered increasing scholarly attention in the field of photocatalysis. Herein, we have successfully designed a metal-free photocatalyst by integrating mesoporous carbon nitride (mpg-C3N4) and C60 through a straightforward and innovative method, marking the first instance of such an achievement. Under red light, the C60/mpg-C3N4 composite exhibited a significantly accelerated rhodamine B (RhB) photodecomposition rate, surpassing bulk g-C3N4 by more than 25.8 times and outperforming pure mpg-C3N4 by 7.8 times. The synergistic effect of C60 and the mesoporous structure significantly enhanced the photocatalytic performance of g-C3N4 by adjusting its electronic structure, broadening the light absorption range, increasing the active sites, and reducing the recombination of photogenerated carriers. This work presents a promising avenue for harnessing a metal-free, stable, efficient photocatalyst driven by red light, with potential for enhancing solar energy utilization in environmental remediation.

P-N Bonds-Mediated Atomic-Level Charge-Transfer Channel Fabricated between Violet Phosphorus and Carbon Nitride Favors Charge Separation and Water Splitting

Heterostructures are widely employed in photocatalysis to promote charge separation and photocatalytic activity. However, their benefits are limited by the linkages and contact environment at the interface. Herein, violet phosphorus quantum dots (VPQDs) and graphitic carbon nitride (g-C3N4) are employed as model materials to form VPQDs/g-C3N4 heterostructures by a simple ultrasonic pulse excitation method. The heterostructure contains strong interfacial P-N bonds that mitigate interfacial charge-separation issues. P-P bond breakage occurs in the distinctive cage-like [P9] VPQD units during longitudinal disruption, thereby exposing numerous active P sites that bond with N atoms in g-C3N4 under ultrasonic pulse excitation. The atomic-level interfacial P-N bonds of the Z-scheme VPQDs/g-C3N4 heterostructure serve as photogenerated charge-transfer channels for improved electron-hole separation efficiency. This results in excellent photocatalytic performance with a hydrogen evolution rate of 7.70 mmol g-1 h-1 (over 9.2 and 8.5 times greater than those of pure g-C3N4 and VPQDs, respectively) and apparent quantum yield of 11.68% at 400 nm. Using atomic-level chemical bonds to promote interfacial charge separation in phosphorene heterostructures is a feasible and effective design strategy for photocatalytic water-splitting materials.

Plasmonic Near-Infrared-Response S-Scheme ZnO/CuInS2 Photocatalyst for H2O2 Production Coupled with Glycerin Oxidation

Solar fuel synthesis is intriguing because solar energy is abundant and this method compensates for its intermittency. However, most photocatalysts can only absorb UV-to-visible light, while near-infrared (NIR) light remains unexploited. Surprisingly, the charge transfer between ZnO and CuInS2 quantum dots (QDs) can transform a NIR-inactive ZnO into a NIR-active composite. This strong response is attributed to the increased concentration of free charge carriers in the p-type semiconductor at the interface after the charge migration between ZnO and CuInS2, enhancing the localized surface plasmon resonance (LSPR) effect and the NIR response of CuInS2. As a paradigm, this ZnO/CuInS2 heterojunction is used for H2O2 production coupled with glycerin oxidation and demonstrates supreme performance, corroborating the importance of NIR response and efficient charge transfer. Mechanistic studies through contact potential difference (CPD), Hall effect test, and finite element method (FEM) calculation allow for the direct correlation between the NIR response and charge transfer. This approach bypasses the general light response issues, thereby stepping forward to the ambitious goal of harnessing the entire solar spectrum.

Efficient wide-spectrum one-dimensional MWO4 (M = Mn, Co, and Cd) photocatalysts: Synthesis, characterization and density functional theory study

Broadening the absorption region to near-infrared (NIR) light is critical for the photocatalysis due to the larger proportion and stronger penetration of NIR light in solar energy. In the present paper, one-dimensional (1D) MWO4 (M = Mn, Co, and Cd) materials synthesized by electrospinning technique, were studied by combining the density functional theory (DFT) with experiment results, which possessed the enhanced light absorption capability within the range of 200-2000 nm. It was proved that in the ultraviolet-visible (UV-Vis) region, the absorption bands of CoWO4 and MnWO4 samples were attributed to the metal-to-metal charge transfer mechanism, while the absorption of CdWO4 sample may be referable to the ligand-to-metal charge transfer mechanism. In the near-infrared (NIR) region, the absorption of CoWO4 and MnWO4 primarily originated from the d-d orbital transitions of Mn2+ and Co2+. The photocatalytic experimental results showed that the degradation rates for bisphenol A (BPA) over CoWO4, MnWO4, and CdWO4 photocatalysts under UV-Vis/NIR light irradiation for 140 min/12 h were 78.8 %/75.9 %, 23.8 %/21.3 %, 12.8 %/8.7 %, respectively. This research offers the novel insights into the precise construction of tungstate catalytic systems and contributes to the advancement of UV-Vis-NIR full spectrum photocatalytic technology, and lays a foundation for a cleaner and more environmental-friendly future.

Near-Infrared Light-Driven Photocatalysis with an Emphasis on Two-Photon Excitation: Concepts, Materials, and Applications

Efficient utilization of sunlight in photocatalysis is widely recognized as a promising solution for addressing the growing energy demand and environmental issues resulting from fossil fuel consumption. Recently, there have been significant developments in various near-infrared (NIR) light-harvesting systems for artificial photosynthesis and photocatalytic environmental remediation. This review provides an overview of the most recent advancements in the utilization of NIR light through the creation of novel nanostructured materials and molecular photosensitizers, as well as modulating strategies to enhance the photocatalytic processes. A special focus is given to the emerging two-photon excitation NIR photocatalysis. The unique features and limitations of different systems are critically evaluated. In particular, it highlights the advantages of utilizing NIR light and two-photon excitation compared to UV-visible irradiation and one-photon excitation. Ongoing challenges and potential solutions for the future exploration of NIR light-responsive materials are also discussed.

Advances in NIR-Responsive Natural Macromolecular Hydrogel Assembly Drugs for Cancer Treatment

Cancer is a serious disease with an abnormal proliferation of organ tissues; it is characterized by malignant infiltration and growth that affects human life. Traditional cancer therapies such as resection, radiotherapy and chemotherapy have a low cure rate and often cause irreversible damage to the body. In recent years, since the traditional treatment of cancer is still very far from perfect, researchers have begun to focus on non-invasive near-infrared (NIR)-responsive natural macromolecular hydrogel assembly drugs (NIR-NMHADs). Due to their unique biocompatibility and extremely high drug encapsulation, coupling with the spatiotemporal controllability of NIR, synergistic photothermal therapy (PTT), photothermal therapy (PDT), chemotherapy (CT) and immunotherapy (IT) has created excellent effects and good prospects for cancer treatment. In addition, some emerging bioengineering technologies can also improve the effectiveness of drug delivery systems. This review will discuss the properties of NIR light, the NIR-functional hydrogels commonly used in current research, the cancer therapy corresponding to the materials encapsulated in them and the bioengineering technology that can assist drug delivery systems. The review provides a constructive reference for the optimization of NIR-NMHAD experimental ideas and its application to human body.

Photocatalytic microbial disinfection under indoor conditions: Prospects and challenges of near IR-photoactive materials

The accumulation of microbes especially in the air and in water bodies is causing the major disease outbreaks. Indoor environment remediation methods are necessary today to clean up these microbes. Among the remediation methods available, in situ generation of highly reactive and oxidizing radical species by advanced oxidation processes (AOPs) inactivate most of the microbes unselectively. Of these AOPs, photocatalytic microbial disinfection especially under indoor conditions is of great interest to maintain microbe-free indoor environment. For efficient microbes' inactivation under indoor conditions, the near IR and IR response of the photocatalysts must be improved. Though the photocatalytic disinfection of microbes using semiconductor-based photocatalysts has been extensively investigated, most of the photocatalysts that have been investigated are either weekly responsive or totally not irresponsive to IR photons due to inappropriate bandgap energies. Several strategies have been investigated to enhance the light harvesting properties of semiconductor based photocatalysts under indoor conditions and make them active to near IR and IR radiations. This review summarizes the recent progress in the field of materials for photocatalysts employed for microbial removal in indoor environments over the past decade as well as outlines key perspectives to enlighten future researches. The paper details the fundamentals of photocatalysis and basic properties of photocatalytic materials in the disinfection of common microbes under indoor conditions. The applications of photocatalytic materials in the disinfection of microbes in indoor environmental conditions are discussed and reviewed. Finally, the remaining challenges and future strategies/prospects in the design and synthesis of IR (and near IR) responsive photocatalysts are discussed.

Synthesis and Photocatalytic Activity of Novel Polycyclopentadithiophene

A novel π-conjugated polymer based on cyclopentadithiophene (CPDT) and poly(4,4']-(((4Hcyclopenta[2,1-b:3,4-b']dithiophene-4,4-diyl)bis(ethane-2,1-diyl))bis(oxy))bis(4-oxobutanoic acid)) (PCPDT-CO2H) was prepared as a sparingly soluble material. The generation of hydroxyl radicals from PCPDT-CO2H in water was confirmed by using coumarin as a hydroxyl radical indicator. Furthermore, PCPDT-CO2H was found to catalyze the oxidative hydroxylation of arylboronic acid and the oxidation of benzaldehyde, indicating that PCPDT-CO2H can be a promising candidate for metal-free and 100% organic heterogeneous photocatalysts.

A machine learning-based nano-photocatalyst module for accelerating the design of Bi2WO6/MIL-53(Al) nanocomposites with enhanced photocatalytic activity

It is a great challenge to acquire novel Bi2WO6/MIL-53(Al) (BWO/MIL) nanocomposites with excellent catalytic activity by the trial-and-error method in the vast untapped synthetic space. The degradation rate of Rhodamine B dye (DRRhB) can be used as the main parameter to evaluate the catalytic activity of BWO/MIL nanocomposites. In this work, a machine learning-based nano-photocatalyst module was developed to speed up the design of BWO/MIL with desirable performance. Firstly, the DRRhB dataset was constructed, and four key features related to the synthetic conditions of BWO/MIL were filtered by the forward feature selection method based on support vector regression (SVR). Secondly, the SVR model with radical basis function for predicting the DRRhB of BWO/MIL was established with the key features and optimal hyperparameters. The correlation coefficients (R) between predicted and experimental DRRhB were 0.823 and 0.884 for leave-one-out cross-validation (LOOCV) and the external test, respectively. Thirdly, potential BWO/MIL nanocomposites with higher DRRhB were discovered by inverse projection, the prediction model, and virtual screening from the synthesis space. Meanwhile, an online web service (http://1.14.49.110/online_predict/BWO2) was built to share the model for predicting the DRRhB of BWO/MIL. Moreover, sensitivity analysis was brought into boosting the model's explainability and illustrating how the DRRhB of BWO/MIL changes over the four key features, respectively. The method mentioned here can provide valuable clues to develop new nanocomposites with the desired properties and accelerate the design of nano-photocatalysts.

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.

Enhancement of Charge Separation and NIR Light Harvesting through Construction of 2D-2D Bi4 O5 I2 /BiOBr:Yb3+ , Er3+ Z-Scheme Heterojunctions for Improved Full-Spectrum Photocatalytic Performance

Developing full-spectrum photocatalysts with simultaneous broadband light absorption, excellent charge separation, and high redox capabilities is becoming increasingly significant. Herein, inspired by the similarities in crystalline structures and compositions, a unique 2D-2D Bi₄ O₅ I₂ /BiOBr:Yb³⁺ ,Er³⁺ (BI-BYE) Z-scheme heterojunction with upconversion (UC) functionality is successfully designed and fabricated. The co-doped Yb³⁺ and Er³⁺ harvest near-infrared (NIR) light and then convert it into visible light via the UC function, expanding the optical response range of the photocatalytic system. The intimate 2D-2D interface contact provides more charge migration channels and enhances the Förster resonant energy transfer of BI-BYE, leading to significantly improved NIR light utilization efficiency. Density functional theory (DFT) calculations and experimental results confirm that the Z-scheme heterojunction is formed and that this heterojunction endows the BI-BYE heterostructure with high charge separation and strong redox capability. Benefit from these synergies, the optimized 75BI-25BYE heterostructure exhibits the highest photocatalytic performance for Bisphenol A (BPA) degradation under full-spectrum and NIR light irradiation, outperforming BYE by 6.0 and 5.3 times, respectively. This work paves an effective approach for designing highly efficient full-spectrum responsive Z-scheme heterojunction photocatalysts with UC function.

Near-Infrared Light Driven ZnIn2S4-Based Photocatalysts for Environmental and Energy Applications: Progress and Perspectives

Zinc indium sulfide (ZnIn₂S₄), as a significant visible-light-responsive photocatalyst, has become a research hotspot to tackle energy demand and environmental issues owing to its excellent properties of high stability, easy fabrication, and remarkable catalytic activity. However, its drawbacks, including low utilization of solar light and fast photoinduced charge carriers, limit its applications. Promoting the response for near-infrared (NIR) light (~52% solar light) of ZnIn₂S₄-based photocatalysts is the primary challenge to overcome. In this review, various modulation strategies of ZnIn₂S₄ have been described, which include hybrid with narrow optical gap materials, bandgap engineering, up-conversion materials, and surface plasmon materials for enhanced NIR photocatalytic performance in the applications of hydrogen evolution, pollutants purification, and CO₂ reduction. In addition, the synthesis methods and mechanisms of NIR light-driven ZnIn₂S₄-based photocatalysts are summarized. Finally, this review presents perspectives for future development of efficient NIR photon conversion of ZnIn₂S₄-based photocatalysts.

A Systematic Review of Advanced Sensor Technologies for Non-Destructive Testing and Structural Health Monitoring

This paper reviews recent advances in sensor technologies for non-destructive testing (NDT) and structural health monitoring (SHM) of civil structures. The article is motivated by the rapid developments in sensor technologies and data analytics leading to ever-advancing systems for assessing and monitoring structures. Conventional and advanced sensor technologies are systematically reviewed and evaluated in the context of providing input parameters for NDT and SHM systems and for their suitability to determine the health state of structures. The presented sensing technologies and monitoring systems are selected based on their capabilities, reliability, maturity, affordability, popularity, ease of use, resilience, and innovation. A significant focus is placed on evaluating the selected technologies and associated data analytics, highlighting limitations, advantages, and disadvantages. The paper presents sensing techniques such as fiber optics, laser vibrometry, acoustic emission, ultrasonics, thermography, drones, microelectromechanical systems (MEMS), magnetostrictive sensors, and next-generation technologies.

Functionalized MOF-Based Photocatalysts for CO2 Reduction

Metal-organic frameworks (MOFs) materials have become a research forefront in the field of photocatalytic CO₂ reduction attributed to their ultra-high specific surface area, adjustable structure, and abundant catalytic active sites. Particularly, MOFs can be facilely tuned to match CO₂ photoreduction by utilizing post-modification of metal nodes, functionalization of organic linkers, and combination with other active materials. Herein, the recent advances in the construction strategy of MOF-based photocatalysts materials for CO₂ reduction are highlighted. Some systematic modification strategies on MOF-based photocatalysts are also discussed, such as modification of metal sites and organic ligands, construction of heterojunction, introduction of single/dual-atom, and strain engineering. Finally, the future development directions of MOF-based photocatalysts in the field of CO₂ reduction are presented.

Photocatalytic degradation of tetracycline hydrochloride with g-C3N4/Ag/AgBr composites

Graphite carbon nitride (g-C₃N₄), as a polymer semiconductor photocatalyst, is widely used in the treatment of photocatalytic environmental pollution. In this work, a Z-scheme g-C₃N₄/Ag/AgBr heterojunction photocatalyst was prepared based on the preparation of a g-C₃N₄-based heterojunction via in-situ loading through photoreduction method. The g-C₃N₄/Ag/AgBr composite showed an excellent photocatalytic performance in the degradation of tetracycline hydrochloride pollutants. Among the prepared samples, g-C₃N₄/Ag/AgBr-8% showed the best photocatalytic ability for the degradation of tetracycline hydrochloride, whose photocatalytic degradation kinetic constant was 0.02764 min^-1, which was 9.8 times that of g-C₃N₄, 2.4 times that of AgBr, and 1.9 times that of Ag/AgBr. In the photocatalytic process, ^•O^2- and ^•OH are main active oxygen species involved in the degradation of organic pollutants. The photocatalytic mechanism of g-C₃N₄/Ag/AgBr is mainly through the formation of Z-scheme heterojunctions, which not only effectively improves the separation efficiency of photogenerated electron-hole pairs, but also maintains the oxidation and reduction capability of AgBr and g-C₃N₄, respectively.

Metallic zirconium carbide mediated near-infrared driven photocatalysis and photothermal sterilization for multidirectional water purification

Undoubtedly, taking full advantage of near-infrared light (NIR) for the photocatalytic reaction is a promising way to realize the efficient utilization of solar energy. In this work, zirconium carbide (ZrC) has been exploited as a NIR-driven photoactive substance for the simultaneous photodegradation of organic pollutants and photothermal sterilization of Escherichia coli (E. coli). The metallic nature and NIR-responsive localized surface plasmon resonance (LSPR) behaviors of ZrC are revealed by both experimental evidence and density function theory (DFT) calculations. ZrC exhibits extremely wide spectral absorbance, excellent NIR-triggered photosensitive effect and photothermal conversion efficiency. Activation kinetics was performed with DFT to investigate the activation process of O₂ to •O₂^-. In addition, a possible NIR-mediated photocatalytic mechanism of ZrC was proposed on the basis of above DFT simulation and radical scavenging experiments. Metallic ZrC with NIR-responsive activity provides a new perspective for designing full-spectrum-driven photocatalysts.

Recent Developments in Heterogeneous Photocatalysts with Near-Infrared Response

Photocatalytic technology has been considered as an efficient protocol to drive chemical reactions in a sustainable and green way. With the assistance of semiconductor-based materials, heterogeneous photocatalysis converts solar energy directly into chemical energy that can be readily stored. It has been employed in several fields including CO2 reduction, H2O splitting, and organic synthesis. Given that near-infrared (NIR) light occupies 47% of sunlight, photocatalytic systems with a NIR response are gaining more and more attention. To enhance the solar-to-chemical conversion efficiency, precise regulation of the symmetric/asymmetric nanostructures and band structures of NIR-response photocatalysts is indispensable. Under the irradiation of NIR light, the symmetric nano-morphologies (e.g., rod-like core-shell shape), asymmetric electronic structures (e.g., defect levels in band gap) and asymmetric heterojunctions (e.g., PN junctions, semiconductor-metal or semiconductor-dye composites) of designed photocatalytic systems play key roles in promoting the light absorption, the separation of electron/hole pairs, the transport of charge carriers to the surface, or the rate of surface photocatalytic reactions. This review will comprehensively analyze the four main synthesis protocols for the fabrication of NIR-response photocatalysts with improved reaction performance. The design methods involve bandgap engineering for the direct utilization of NIR photoenergy, the up-conversion of NIR light into ultraviolet/visible light, and the photothermal effect by converting NIR photons into local heat. Additionally, challenges and perspectives for the further development of heterogeneous photocatalysts with NIR response are also discussed based on their potential applications.

Hollow Nanoboxes Cu2-x S@ZnIn2 S4 Core-Shell S-Scheme Heterojunction with Broad-Spectrum Response and Enhanced Photothermal-Photocatalytic Performance

Major issues in photocatalysis include improving charge carrier separation efficiency at the interface of semiconductor photocatalysts and rationally developing efficient hierarchical heterostructures. Surface continuous growth deposition is used to make hollow Cu_2-x S nanoboxes, and then simple hydrothermal reaction is used to make core-shell Cu_2-x S@ZnIn₂ S₄ S-scheme heterojunctions. The photothermal and photocatalytic performance of Cu_2-x S@ZnIn₂ S₄ is improved. In an experimental hydrogen production test, the Cu_2-x S@ZnIn₂ S₄ photocatalyst produces 4653.43 µmol h^-1 g^-1 of hydrogen, which is 137.6 and 13.8 times higher than pure Cu_2-x S and ZnIn₂ S₄ , respectively. Furthermore, the photocatalyst exhibits a high tetracycline degradation efficiency in the water of up to 98.8%. For photocatalytic reactions, the hollow core-shell configuration gives a large specific surface area and more reactive sites. The photocatalytic response range is broadened, infrared light absorption enhanced, the photothermal effect is outstanding, and the photocatalytic process is promoted. Meanwhile, characterizations, degradation studies, active species trapping investigations, energy band structure analysis, and theoretical calculations all reveal that the S-scheme heterojunction can efficiently increase photogenerated carrier separation. This research opens up new possibilities for future S-scheme heterojunction catalyst design and development.

Breaking the Limitation of Elevated Coulomb Interaction in Crystalline Carbon Nitride for Visible and Near-Infrared Light Photoactivity

Most near-infrared (NIR) light-responsive photocatalysts inevitably suffer from low charge separation due to the elevated Coulomb interaction between electrons and holes. Here, an n-type doping strategy of alkaline earth metal ions is proposed in crystalline K⁺ implanted polymeric carbon nitride (KCN) for visible and NIR photoactivity. The n-type doping significantly increases the electron densities and activates the n→π* electron transitions, producing NIR light absorption. In addition, the more localized valence band (VB) and the regulation of carrier effective mass and band decomposed charge density, as well as the improved conductivity by 1-2 orders of magnitude facilitate the charge transfer and separation. The proposed n-type doping strategy improves the carrier mobility and conductivity, activates the n→π* electron transitions for NIR light absorption, and breaks the limitation of poor charge separation caused by the elevated Coulomb interaction.

Photochemical α-Aminonitrile Synthesis Using Zn-Phthalocyanines as Near-Infrared Photocatalysts

While photochemical transformations with sunlight almost exclusively utilize the UV-vis part of the solar spectrum, the majority of the photons emitted by the sun have frequencies in the near-infrared region. Phthalocyanines show high structural similarity to the naturally occurring light-harvesting porphyrins, chlorins, and mainly bacteriochlorins and are also known for being efficient and affordable near-infrared light absorbers as well as triplet sensitizers for the production of singlet oxygen. Although having been neglected for a long time in synthetic organic chemistry due to their low solubility and high tendency toward aggregation, their unique photophysical properties and chemical robustness make phthalocyanines attractive photocatalysts for the application in near-infrared-light-driven synthesis strategies. Herein, we report a cheap, simple, and efficient photocatalytic protocol, which is easily scalable under continuous-flow conditions. Various phthalocyanines were studied as near-infrared photosensitizers in oxidative cyanations of tertiary amines to generate α-aminonitriles, a synthetically versatile compound class.

Emerging S-Scheme Photocatalyst

Photocatalysis is a green technology to use ubiquitous and intermittent sunlight. The emerging S-scheme heterojunction has demonstrated its superiority in photocatalysis. This article covers the state-of-the-art progress and provides new insights into its general designing criteria. It starts with the challenges confronted by single photocatalyst from the perspective of energy dissipation by borrowing the common behaviors in the dye molecule. Subsequently, other problems faced by single photocatalyst are summarized. Then a viable solution for these problems is the construction of heterojunctions. To overcome the problems and mistakes of type-II and Z-scheme heterojunctions, S-scheme heterojunction is proposed and the underlying reaction mechanism is summarized. Afterward, the design principles for S-scheme heterojunction are proposed and four types of S-scheme heterojunctions are suggested. Following this, direct characterization techniques for testifying the charge transfer in S-scheme heterojunction are presented. Finally, different photocatalytic applications of S-scheme heterojunctions are summarized. Specifically, this work endeavors to clarify the critical understanding on curved Fermi level in S-scheme heterojunction interface, which can help strengthen and advance the fundamental theories of photocatalysis. Moreover, the current challenges and prospects of the S-scheme heterojunction photocatalyst are critically discussed.

Metal free benzothiadiazole-diketopyrrolopyrrole-based conjugated polymer/g-C3N4 photocatalyst for enhanced sterilization and degradation in visible to near-infrared region

In recent years, photocatalytic technology has attracted wide attention in environmental treatment, exploring non-toxic and metal-free photocatalysts is imminent to meet sustainable development. However, semiconductors with wide spectral response are rarely studied and applied in the field of photocatalysis. Herein, a new narrow band-gap polymer PFBDT-DPP (P3) with wide absorption from 500 to 860 nm was synthesized and further constructed heterostructure with g-C₃N₄ for photocatalytic sterilization and degradation of organic pollutant Rhodamine B (RhB). The optimal antibacterial rate for Escherichia coli reached 99.8% after 190 min of light irradiation and for Staphylococcus aureus reached 96.8% after 120 min of irradiation, and the highest degradation efficiency of RhB by P3/g-C₃N₄ was 98.9% within 60 min light irradiation, while g-C₃N₄ displayed an unsatisfactory sterilization and photodegradation performance. This is mainly attributed to the broadened light absorption range and enhanced carrier separation efficiency of P3/g-C₃N₄. This work could provide a new strategy to fabricate metal-free photocatalysts with high utilization of sunlight and excellent photocatalytic performance.

Inorganic Metal-Oxide Photocatalyst for H2 O2 Production

Hydrogen peroxide (H₂ O₂ ) is a mild but versatile oxidizing agent with extensive applications in bleaching, wastewater purification, medical treatment, and chemical synthesis. The state-of-art H₂ O₂ production via anthraquinone oxidation is hardly considered a cost-efficient and environment-friendly process because it requires high energy input and generates hazardous organic wastes. Photocatalytic H₂ O₂ production is a green, sustainable, and inexpensive process which only needs water and gaseous dioxygen as the raw materials and sunlight as the power source. Inorganic metal oxide semiconductors are good candidates for photocatalytic H₂ O₂ production due to their abundance in nature, biocompatibility, exceptional stability, and low cost. Progress has been made to enhance the photocatalytic activity toward H₂ O₂ production, however, H₂ O₂ photosynthesis is still in the laboratory research phase since the productivity is far from satisfaction. To inspire innovative ideas for boosting the H₂ O₂ yield in photocatalysis, the most well-studied metal oxide photocatalysts are selected and the modification strategies to improve their activity are listed. The mechanisms for H₂ O₂ production over modified photocatalysts are discussed to highlight the facilitating role of the modification methods. Besides, methods for the quantification of H₂ O₂ and associated radical intermediates are provided to guide future studies in this field.

Cyanamide defects induced built-in electric field in crystalline carbon nitride for enhanced visible to near infrared light photocatalytic activity

Carbon nitride materials have achieved high accomplishments in solar to hydrogen energy conversion under visible light. However, the weak kinetics and rapid recombination of photogenerated charge carriers result in a...

Photocatalytic H2 Evolution Coupled with Furfuralcohol Oxidation over Pt-Modified ZnCdS Solid Solution

Coupling photocatalytic H₂ production with organic synthesis attracts immense interest in the energy and chemical engineering field for the low-cost, clean, and sustainable generation of green energy and value-added products. Nevertheless, the performance of current photocatalysts is greatly limited by grievous charge recombination and tardy H₂ evolution. To tackle these issues, a Pt nanocluster-modified ZnCdS solid solution is fabricated for photocatalytic H₂ production and selective furfuralcohol oxidation. The internal electric field inside the ZnCdS and Schottky junction between ZnCdS and Pt nanoclusters drastically ameliorate charge separation. Meanwhile, the Pt nanoclusters remarkably expedite the H₂ evolution kinetics on ZnCdS. As a result, the H₂ production rate over Pt-loaded ZnCdS reaches 1045 µmol g^-1 h^-1 , which is about 26- and 70-fold that of CdS and ZnS, respectively. Under light irradiation for 3 h, the conversion of furfuralcohol to furfural reaches 71% with 89% furfural selectivity. The photocatalytic mechanism is investigated by in situ characterizations and theoretical calculations.

Influence of calcination temperature on photocatalytic H2O2productivity of hierarchical porous ZnO microspheres

Photocatalytic production of H₂O₂from water and atmospheric oxygen has been recognized as a green and sustainable chemical process, due to the abundance of raw materials and sustainable solar energy. Herein, flower-like hierarchical ZnO microspheres were prepared by hydrothermal method followed by calcination at different temperatures, and their photocatalytic performance in H₂O₂production was examined under simulated sunlight irradiation. The calcination temperature plays a vital role in the structure, morphology, and surface area of the final ZnO products as well as their optical and electrochemical properties, which are determining factors in their photocatalytic activity. The ZnO calcined at 300 °C (Zn-300) exhibits the highest activity and optimal stability, showing productivity of 2793μmol l^-1within 60 min of irradiation, which was 6.5 times higher than that of uncalcined ZnO precursor. The remarkable photocatalytic activity is attributed to enhanced light utilization, large surface area, abundant exposed active sites, improved separation efficiency, and prolonged carrier lifespan. Moreover, the results from cycling experiments indicate the as-prepared ZnO samples exhibit good stability and long-time performance. This work provides useful information for the preparation of hierarchical ZnO photocatalysts.

Interfacial Design to Enhance Photocatalytic Hydrogen Evolution via Optimizing Energy and Mass Flows

Energy and mass transfer in photocatalytic systems plays a significant role in photocatalytic water splitting, but relevant research has long been ignored. Here, an interfacial photocatalytic mode for photocatalytic hydrogen production is exploited to optimize the energy and mass flows and mainly includes a heat-insulating layer, a water-channel layer, and a photothermal photocatalytic layer. In this mode, the energy flow is optimized for efficient spreading, conversion, and utilization. A low-loss path (ultrathin water film) and an efficient heat localized zone are constructed, where light energy, especially infrared-light energy, can transfer to the target functional membrane surface with low loss and the thermal energy converted from light can be localized for further use. Meanwhile, the optimization of the mass flow is achieved by improving the desorption capacity of the products. The generated hydrogen bubbles can rapidly leave from the surface of the photocatalyst, along with the active sites being released timely. Consequently, the photocatalytic hydrogen production rate can be increased up to about 6.6 times that in a conventional photocatalytic mode. From the system design aspect, this work provides an efficient strategy to improve the performance of photocatalytic water splitting by optimizing the energy and mass flows.