Conjugated diamine cation based halide perovskitoid enables robust stability and high photodetector performance.

Low-dimensional lead halide materials have proved to be intrinsically stable semiconductor materials. However, the development of one-dimensional (1D) perovskites or perovskitoids with both robust water stability and high optoelectronic performance still faces significant challenges. Here, we report a new class of 1D (TzBIPY)Pb2X6 (X = Cl, Br, I) perovskitoids featuring a π-conjugated diamine cation (TzBIPY = 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole). The TzBIPY2+ cation with delocalized electrons directly contributes to the electronic structure and hence reduces the band gap. Especially, the Br-based material exhibits enhanced carrier separation and transport capacity, benefiting from the improved electronic conjugation together with a type II intramolecular heterojunction between conjugated organic cations and Pb-X octahedra. The (TzBIPY)Pb2Br6 photodetector exhibits an impressive photocurrent on/off ratio of 8.1 × 105, which is much superior to the previous three-dimensional (3D) perovskite benchmark. Additionally, the π-conjugated cations serve as dense protective shields for vulnerable Pb-X inorganic lattice against being attacked by water, thus demonstrating exceptional stability even immersed in water for over 3000 h.

Facile Synthesis of Organic-Inorganic Hybrid Heterojunctions of Glycolated Conjugated Polymer-TiO2-X for Efficient Photocatalytic Hydrogen Evolution.

The utilization of the organic-inorganic hybrid photocatalysts for water splitting has gained significant attention due to their ability to combine the advantages of both materials and generate synergistic effects. However, they are still far from practical application due to the limited understanding of the interactions between these two components and the complexity of their preparation process. Herein, a facial approach by combining a glycolated conjugated polymer with a TiO2-X mesoporous sphere to prepare high-efficiency hybrid photocatalysts is presented. The functionalization of conjugated polymers with hydrophilic oligo (ethylene glycol) side chains can not only facilitate the dispersion of conjugated polymers in water but also promote the interaction with TiO2-X forming stable heterojunction nanoparticles. An apparent quantum yield of 53.3% at 365 nm and a hydrogen evolution rate of 35.7 mmol h-1 g-1 is achieved by the photocatalyst in the presence of Pt co-catalyst. Advanced photophysical studies based on femtosecond transient absorption spectroscopy and in situ, XPS analyses reveal the charge transfer mechanism at type II heterojunction interfaces. This work shows the promising prospect of glycolated polymers in the construction of hybrid heterojunctions for photocatalytic hydrogen production and offers a deep understanding of high photocatalytic performance by such heterojunction photocatalysts.

Na-mediated carbon nitride realizing CO2 photoreduction with selectivity modulation.

The depressed directional separation of photogenerated carriers and weak CO2 adsorption/activation activity are the main factors hampering the development of artificial photosynthesis. Herein, Na ions are embedded in graphitic carbon nitride (g-C3N4) to achieve directional migration of the photogenerated electrons to Na sites, while the electron-rich Na sites enhance CO2 adsorption and activation. Na/g-C3N4 (NaCN) shows improved photocatalytic reduction activity of CO2 to CO and CH4, and under simulated sunlight irradiation, the CO yield of NaCN synthesized by embedding Na at 550°C (NaCN-550) is 371.2 µmol g-1 h-1, which is 58.9 times more than that of the monomer g-C3N4. By means of theoretical calculations and experiments including in situ fourier transform infrared spectroscopy, the mechanism is investigated. This strategy which improves carrier separation and reduces the energy barrier at the same time is important to the development of artificial photosynthesis.

Precise Design of TiO2@CoOx Heterostructure via Atomic Layer Deposition for Synergistic Sono-Chemodynamic Oncotherapy.

Sonodynamic therapy (SDT), a tumor treatment modality with high tissue penetration and low side effects, is able to selectively kill tumor cells by producing cytotoxic reactive oxygen species (ROS) with ultrasound-triggered sonosensitizers. N-type inorganic semiconductor TiO2 has low ROS quantum yields under ultrasound irradiation and inadequate anti-tumor activity. Herein, by using atomic layer deposition (ALD) to create a heterojunction between porous TiO2 and CoOx, the sonodynamic therapy efficiency of TiO2 can be improved. Compared to conventional techniques, the high controllability of ALD allows for the delicate loading of CoOx nanoparticles into TiO2 pores, resulting in the precise tuning of the interfaces and energy band structures and ultimately optimal SDT properties. In addition, CoOx exhibits a cascade of H2O2→O2→·O2 - in response to the tumor microenvironment, which not only mitigates hypoxia during the SDT process, but also contributes to the effect of chemodynamic therapy (CDT). Correspondingly, the synergistic CDT/SDT treatment is successful in inhibiting tumor growth. Thus, ALD provides new avenues for catalytic tumor therapy and other pharmaceutical applications.

Triggering photocatalytic performance of La2CoxMn2-xO6 via heat activation.

The La-based perovskite (LaBO3) exhibits excellent optical properties. However, its valence band (VB) potential is not sufficiently positive to reach the oxidation potential required for the cleavage of chemical bonds (such as benzylic C-H), limiting its application in photocatalysis. Herein, we report the unconventional effects of heat activation on the reduction of the dissociation energy of benzylic C-H and aqueous H-O, thereby triggering the photocatalytic activity of La2CoxMn2-xO6 perovskites. Additionally, we demonstrate that photocatalysis is the main contributor to substrate conversion in the selective oxidation of toluene and reduction of CO2. Particularly, La2Co1.5Mn0.5O6 shows excellent performance with a product yield of 550.00 mmol gcat-1 and a toluene conversion of 22,866.67 µmol gcat-1 h-1. To the best of our knowledge, this is the highest reported product yield for the selective oxidation of benzylic C-H bond of toluene. Our findings provide insight into the specific role of heat activation in photocatalysis, which is crucial for breaking and overcoming the VB barrier to realize challenging reactions.

K-N Bridge-Mediated charge separation in hollow g-C3N4 Frameworks: A bifunctional photocatalysts towards efficient H2 and H2O2 production.

The development of bifunctional photocatalysts for enhancing hydrogen (H2) and hydrogen peroxide (H2O2) production from water is essential in addressing environmental and energy issues. However, the practical implementation of photocatalytic technology is still constrained by the inadequate separation of photo-generated charge carriers. Herein, potassium (K) atoms are introduced into the interlayers of graphitic carbon nitride (g-C3N4) with a hollow hexagonal structure (K-TCN) and are coordinated with N atoms in adjacent layers. The presence of K-N coordination serves as a layer bridge, facilitating the separation of charge carriers. The hollow hexagonal structure reduces the distance over which photogenerated electrons migrate to the surface, thereby enhancing the reaction kinetics. Consequently, the optimized K-TCN exhibits a dramatically improved photocatalytic H2 (941.6 µmol g-1h-1 with platinum (Pt) as the cocatalyst) and H2O2 (347.6 µmol g-1h-1) generation as compared to hollow g-C3N4 (TCN) and bulk g-C3N4 nanosheet (CN) without K-N bridge under visible light irradiation. The unique design holds promising potential for developing highly efficient bifunctional photocatalysts towards producing renewable fuels and value-added chemicals.

Achieving high carrier separation over Bi4O5I2through Ni doping for improved photocatalytic CO2reduction.

Photocatalytic CO2reduction is considered to be an appealing way of alleviating environmental pollution and energy shortages simultaneously under mild condition. However, the activity is greatly limited by the poor separation of the photogenerated carriers. Ion doping is a feasible strategy to facilitate the charge transfer. In this work, Ni-doped Bi4O5I2photocatalyst is successfully fabricated using a one-pot hydrothermal method. A few doping levels appear in the energy band of Bi4O5I2after Ni doping, which are used as springboards for electrons transition, thus promoting photoexcited electrons and holes separation. As a consequence, a remarkably enhanced yield of CO and CH4(6.2 and 1.9µmol g-1h-1) is obtained over the optimized Bi4O5I2-Ni15, which is approximately 2.1 and 3.8 times superior to pure Bi4O5I2, respectively. This work may serve as a model for the subsequent research of Bi-based photocatalysts to implement high-performance CO2photoreduction.

Selective Cocatalyst Decoration of Narrow-Bandgap Broken-Gap Heterojunction for Directional Charge Transfer and High Photocatalytic Properties.

Narrow-bandgap semiconductors are promising photocatalysts facing the challenges of low photoredox potentials and high carrier recombination. Here, a broken-gap heterojunction Bi/Bi2 S3 /Bi/MnO2 /MnOx , composed of narrow-bandgap semiconductors, is selectively decorated by Bi, MnOx nanodots (NDs) to achieve robust photoredox ability. The Bi NDs insertion at the Bi2 S3 /MnO2 interface induces a vertical carrier migration to realize sufficient photoredox potentials to produce O2 •- and • OH active species. The surface decoration of Bi2 S3 /Bi/MnO2 by Bi and MnOx cocatalysts drives electrons and holes in opposite directions for optimal photogenerated charge separation. The selective cocatalysts decoration realizes synergistic surface and bulk phase carrier separation. Density functional theory (DFT) calculation suggests that Bi and MnOx NDs act as active sites enhancing the absorption and reactants activation. The decorated broken-gap heterojunction demonstrates excellent performance for full-light driving organic pollution degradation with great commercial application potential.

Tuning the Microstructures of ZnO To Enhance Photocatalytic NO Removal Performances.

Effective removal of kinetically inert dilute nitrogen oxide (NO, ppb) without NO2 emission is still a challenging topic in environmental pollution control. One effective approach to reducing the harm of NO is the construction of photocatalysts with diversified microstructures and atomic arrangements that could promote adsorption, activation, and complete removal of NO without yielding secondary pollution. Herein, microstructure regulations of ZnO photocatalysts were attempted by altering the reaction temperature and alkalinity in a unique ionic liquid-based solid-state synthesis and further investigated for the removal of dilute NO upon light irradiation. Microstructure observations indicated that as-tuned photocatalysts displayed unique nucleation, diverse morphologies (spherical nanoparticles, short and long nanorods), defect-related optical characteristics, and enhanced carrier separations. Such defect-related surface-interface aspects, especially Vo″-related defects of ZnO devoted them to the 4.16-fold enhanced NO removal and 2.76 magnitude order decreased NO2 yields, respectively. Improved NO removal and toxic product inhabitation in as-tuned ZnO was disclosed by mechanistic exploitations. It was revealed that regulated microstructures, defect-related charge carrier separation, and strengthened surface interactions were beneficial to active species production and molecular oxygen activation in ZnO, subsequently contributing to the improved NO removal and simultaneous avoidance of NO2 formation. This investigation shed light on the facile regulation of microstructures and the roles of surface chemistry in the oxidation of low concentration NO in the ppb level upon light illumination.

Highly Efficient and Exceptionally Durable Photooxidation Properties on Co3O4/g-C3N4 Surfaces.

Water pollution is a significant social issue that endangers human health. The technology for the photocatalytic degradation of organic pollutants in water can directly utilize solar energy and has a promising future. A novel Co3O4/g-C3N4 type-II heterojunction material was prepared by hydrothermal and calcination strategies and used for the economical photocatalytic degradation of rhodamine B (RhB) in water. Benefitting the development of type-II heterojunction structure, the separation and transfer of photogenerated electrons and holes in 5% Co3O4/g-C3N4 photocatalyst was accelerated, leading to a degradation rate 5.8 times higher than that of pure g-C3N4. The radical capturing experiments and ESR spectra indicated that the main active species are •O2- and h+. This work will provide possible routes for exploring catalysts with potential for photocatalytic applications.

Fabrication of Noble-Metal-Free Mo2C/CdIn2S4 Heterojunction Composites with Elevated Carrier Separation for Photocatalytic Hydrogen Production.

Molybdenum-based cocatalyst being used to construct heterojunctions for efficient photocatalytic H2 production is a promising research hotspot. In this work, CdIn2S4 was successfully closely supported on bulk Mo2C via the hydrothermal method. Based on their matching band structures, they formed a Type Ⅰ heterojunction after the combination of Mo2C (1.1 eV, -0.27 V, 0.83 V) and CdIn2S4 (2.3 eV, -0.74 V, 1.56 V). A series of characterizations proved that the heterojunction composite had higher charge separation efficiency compared to a single compound. Meanwhile, Mo2C in heterojunction could act as an active site for hydrogen production. The photocatalytic H2 production activity of the heterojunction composites was significantly improved, and the maximum activity was up to 1178.32 µmmol h-1 g-1 for 5Mo2C/CdIn2S4 composites. 5Mo2C/CdIn2S4 heterojunction composites possess excellent durability in three cycles (loss of 6%). Additionally, the mechanism of increased activity for composites was also investigated. This study provides a guide to designing noble-metal-free photocatalyst for highly efficient photocatalytic H2 evolution.

Investigation of the Photocatalytic Hydrogen Production of Semiconductor Nanocrystal-Based Hydrogels.

Destabilization of a ligand-stabilized semiconductor nanocrystal solution with an oxidizing agent can lead to a macroscopic highly porous self-supporting nanocrystal network entitled hydrogel, with good accessibility to the surface. The previously reported charge carrier delocalization beyond a single nanocrystal building block in such gels can extend the charge carrier mobility and make a photocatalytic reaction more probable. The synthesis of ligand-stabilized nanocrystals with specific physicochemical properties is possible, thanks to the advances in colloid chemistry made in the last decades. Combining the properties of these nanocrystals with the advantages of nanocrystal-based hydrogels will lead to novel materials with optimized photocatalytic properties. This work demonstrates that CdSe quantum dots, CdS nanorods, and CdSe/CdS dot-in-rod-shaped nanorods as nanocrystal-based hydrogels can exhibit a much higher hydrogen production rate compared to their ligand-stabilized nanocrystal solutions. The gel synthesis through controlled destabilization by ligand oxidation preserves the high surface-to-volume ratio, ensures the accessible surface area even in hole-trapping solutions and facilitates photocatalytic hydrogen production without a co-catalyst. Especially with such self-supporting networks of nanocrystals, the problem of colloidal (in)stability in photocatalysis is circumvented. X-ray photoelectron spectroscopy and photoelectrochemical measurements reveal the advantageous properties of the 3D networks for application in photocatalytic hydrogen production.

Construction of Y-Doped BiVO4 Photocatalysts for Efficient Two-Electron O2 Reduction to H2 O2.

Photocatalytic hydrogen peroxide (H2 O2 ) production on BiVO4 photocatalysts using water and oxygen as raw materials is a green and sustainable process. However, the photocatalytic efficiency of pristine BiVO4 is limited by severe charge recombination. In this work, rare earth element Yttrium (Y) doped BiVO4 photocatalysts were fabricated by the hydrothermal method. In the photocatalytic H2 O2 production experiment, the optimized Y-doped BiVO4 photocatalyst produced 114 µmol g-1 h-1 of H2 O2 under simulated sunlight (AM1.5) irradiation, which is four times higher than production activity of pure BiVO4 (26 µmol g-1 h-1 ). Density functional theory (DFT) calculation revealed that Y doping can enhance oxygen adsorption on the BiVO4 photocatalyst surface. Mechanistic investigations suggest that the doping process induces the in situ formation of monoclinic/tetragonal BiVO4 heterojunction, which further promotes the photogenerated carriers separation efficiency.

Dual modification based on electrostatic repulsion of bentonite and SPR effect of Bi facilitate charge transfer of Bi2WO6 for antibiotics degradation.

Development of efficient photocatalysts is vital for light-driven removal of refractory antibiotics. Herein, Bi2WO6 microspheres were successfully anchored on the surface of bentonite, and metallic Bi was reduced in-situ by a one-step solvothermal method. Notably, the Bi/Bi2WO6/BT with a mass ratio of 0.15:1:0.1 exhibited the best photocatalytic activity toward degradation of tetracycline (TC) and ciprofloxacin (CIP) after 120 min of visible light irradiation, and their reaction rate constants were 8.0 and 5.5 folds higher than that of pristine Bi2WO6, respectively. The boosted photocatalytic activity over Bi/Bi2WO6/BT was ascribed to the establishment of electrostatic repulsion and SPR effect, which synergistically promoted charges transfer, thus achieving more h+ and ·O2- radical generation. Moreover, possible TC and CIP degradation pathways over Bi/Bi2WO6/BT were proposed based on the identified intermediates, and most of the intermediates were less toxic than TC and CIP. The study provides options to develop high-efficiency photocatalytic composites for contaminants elimination using semiconductors and readily available bentonite.

An effective strategy for promoting charge separation by integrating heterojunctions and multiple homojunctions in TiO2 nanorods to enhance photoelectrochemical oxygen evolution.

It is important to achieve high photoelectrochemical (PEC) oxygen evolution performance in titanium oxide (TiO2) via the separation and transportation of photogenerated carriers. Herein, three-dimensional (3D) TiO2 nanorod arrays growing on flexible carbon cloth (CC) were decorated with graphitic carbon nitride (g-C3N4) to yield a 3D g-C3N4/TiO2/CC heterojunction composite (TCN). The photocurrent density of TCN is 10.6 times that of the bare TiO2 nanorod arrays, which can be attributed to the promoted separation and transportation of photogenerated carriers by the heterojunction. Then, a simple rapid cooling and heating (RCH) treatment was creatively introduced to form a gradient Ti3+ self-doping TiO2 multiple homojunction (GTSD-TiO2) in the bulk during the hydrothermal growth of the TiO2 nanorod array. This can further facilitate the separation and transportation of carriers in the bulk owing to the formation of a built-in electric field. The GTSD-TiO2 was decorated with g-C3N4 to form a core-shell heterojunction composite (GTSD-TCN). Notably, the photocurrent density of the GTSD-TCN core-shell heterojunction reached 1.23 mA cm-2 at 1.23 V (vs reversible hydrogen electrode (RHE)) under air mass (AM) 1.5 G illumination without the use of hole scavengers or cocatalysts; this was twice the photocurrent density of the TCN heterojunction (0.64 mA cm-2) and is one of the best values obtained from the previously reported TiO2 and g-C3N4 heterojunction. This performance may be ascribed to the enhanced charge separation and transportation efficiency of the heterojunction after the RCH treatment; the efficiency rises from 51 % (TCN) to 71 % (GTSD-TCN). We believe that the RCH treatment is a highly promising method towards fabricating unique multiple homojunctions by gradient self-doping. This simple and novel design provides a new route for the preparation of high-performance PEC photoelectrodes.

Construction of S-Scheme heterojunction Ni11(HPO3)8(OH)6/CdS photocatalysts with open framework surface for enhanced H2 evolution activity.

The emerging S-scheme heterojunction shows a particular superiority in enhancing the efficiency of charge separation in photocatalyst. Herein, a Ni11(HPO3)8(OH)6/CdS heterojunctions (NiPO/CdS) are constructed for the first time by loading open framework structure NiPO on the surface of CdS nanoparticles (CdS NPs). The built-in electric field generated at the interface promotes the directional migration of photogenerated electrons from NiPO to CdS. This S-scheme pathway achieves a strong redox capacity and efficient carrier separation. More importantly, the unique triangular and hexagonal channels of NiPO facilitate the exposure of CdS active sites for proton adsorption, H2 production and escape. The hydrogen evolution rate of NiPO/CdS is 39 mmol g-1 h-1 under visible light irradiation, which is 6.5 times higher than that of pure CdS. The NiPO/CdS heterojunction also exhibits remarkable long-term stability. This study provides a new strategy for the ingenious design of S-scheme photocatalysts with excellent photocatalytic performance.

Efficient Strategy for U(VI) Photoreduction: Simultaneous Construction of U(VI) Confinement Sites and Water Oxidation Sites.

Reduction of hexavalent uranium [U(VI)] by the photocatalytic method opens up a novel way to promote the selectivity, kinetics, and capacity during uranium removal, where organic molecules act as the sacrificial agents. However, the addition of sacrificial agents can cause a secondary environmental pollution and increase the cost. Here, a UiO-66-based photocatalyst (denoted as MnOx/NH2-UiO-66) simultaneously with efficient U(VI) confinement sites and water oxidation sites was successfully developed, achieving excellent U(VI) removal without sacrificial agents. In MnOx/NH2-UiO-66, the amino groups served as efficient U(VI) confinement sites and further decreased the U(VI) reduction potential. Besides, MnOx nanoparticles separated the photogenerated electron-hole pairs and provided water oxidation sites. The U(VI) confinement sites and water oxidation sites jointly promoted the U(VI) photoreduction performance of MnOx/NH2-UiO-66, resulting in the removal ratio of MnOx/NH2-UiO-66 for U(VI) achieving 97.8% in 2 h without hole sacrifice agents. This work not only provides an effective UiO-66-based photocatalyst but also offers a strategy for effective U(VI) photoreduction.

Fabrication of novel and noble-metal-free MoP/In2S3 Schottky heterojunction photocatalyst with efficient charge separation for enhanced photocatalytic H2 evolution under visible light.

Here, we synthesized a series of noble-metal-free MoP/In2S3 Schottky heterojunction photocatalysts through two-step synthesis. Morphology characterization revealed that In2S3 was deposited on metal-like MoP. The electrochemical experiment, photoluminescence (PL) and time-resolved transient PL results verify that electron-hole pairs separation efficiency of MoP-In2S3 composites has been immensely elevated compared to pristine In2S3. The effective separation of photocarriers is attributed to the appropriate Schottky energy barrier, band bending and Fermi level rearrangement between MoP and In2S3. Furthermore, the X-ray photoelectron spectra confirmed that electrons transferred from In2S3 to MoP in Schottky heterojunction. Importantly, MoP possesses active sites for H2 generation resulting from nearly zero binding for H atoms and low onset overpotentials. As expected, the 25 %MoP-In2S3 composites exhibited excellent photocatalytic activity (481.73 µmol·h-1·g-1), which was about 23 times than In2S3-1 %Pt (20.73 µmol·h-1·g-1). Hence, the enhanced photocatalytic performance was ascribed to not only the formed Schottky heterojunction leading to better charge separation, but also MoP as the active sites accelerated the surface proton reduction reaction. The research furnishes a thought that suitable semiconductors and metal-like were selected to construct high performance and low-cost Schottky heterojunction with efficient charge separation and active sites for resultful photocatalytic H2 generation.

Enhanced Photo-Assisted Fenton Degradation of Antibiotics over Iron-Doped Bi-Rich Bismuth Oxybromide Photocatalyst.

Herein, combining photocatalysis and Fenton oxidation, a photo-assisted Fenton system was conducted using Fe-doped Bi4O5Br2 as a highly efficient photocatalyst to realize the complete degradation of Tetracycline antibiotics under visible light. It has been observed that the optimized photocatalyst 5%Fe-doped Bi4O5Br2 exhibits a degradation efficiency of 100% for Tetracycline with H2O2 after 3 h visible-light irradiation, while a degradation percentage of 59.8% over the same photocatalyst and 46.6% over pure Bi4O5Br2 were obtained without the addition of H2O2 (non-Fenton process). It is unambiguous that a boost photo-assisted Fenton system for the degradation of Tetracycline has been established. Based on structural analysis, it demonstrated that the Fe atoms in place of the Bi sites may result in the distortion of the local structure, which induced the occurrence of the spontaneous polarization and thus enhanced the built-in electric field. The charge separation efficiency is enhanced, and the recombination of electrons and holes is inhabited so that more charges are generated to reach the surface of the photocatalyst and therefore improve the photocatalytic degradation efficiency. Moreover, more Fe (II) sites formed on the 5%Fe-Bi4O5Br2 photocatalyst and facilitated the activation of H2O2 to form oxidative species, which greatly enhanced the degradation efficiency of Tetracycline.

Metal-free 2D/2D C3N5/GO nanosheets with customized energy-level structure for radioactive nuclear wastewater treatment.

How to efficiently treat radioactive uranium-containing nuclear wastewater is one of the significant challenges to ensure the safety of nuclear technology and to avoid environmental pollution. Here we firstly prepare the metal-free 2D/2D C3N5/GO nanosheets, and customize a type-II heterojunction based on the band bending theory to achieve enhanced uranium extraction capacity via synergistic adsorption photoreduction engineering. The structure of C3N5 is explained by electron energy loss spectroscopy and synchrotron-based near-edge X-ray absorption fine structure. And C3N5 with larger π-conjugated structure expands the light response range to 747 nm, which is about 1.67 times that of C3N4. Further, we also use density functional theory to prove the existence of alternating energy levels so that photogenerated electrons could be continuously injected into the surface of GO to ensure the effective separation of electron-hole pairs and increase the material activity. The results show that the removal ratio of uranium by 2D/2D C3N5/GO heterojunction is achieved as high as 96.1% even at a low uranium concentration of 10 ppm, and reached 93.4% after exposure to gamma-ray. This work will lay a foundation for customizing the energy band structure of nonmetal-based 2D/2D nanohybrids and enriching uranium-containing wastewater through adsorption photoreduction engineering in the future.