D-A Conjugated Polymer/CdS S-Scheme Heterojunction with Enhanced Interfacial Charge Transfer for Efficient Photocatalytic Hydrogen Generation.

Owing to the improved charge separation and maximized redox capability of the system, Step-scheme (S-scheme) heterojunctions have garnered significant research attention for efficient photocatalysis of H2 evolution. In this work, an innovative linear donor-acceptor (D-A) conjugated polymer fluorene-alt-(benzo-thiophene-dione) (PFBTD) is coupled with the CdS nanosheets, forming the organic-inorganic S-scheme heterojunction. The CdS/PFBTD (CP) composite exhibits an impressed hydrogen production rate of 7.62 mmol g-1  h-1 without any co-catalysts, which is ≈14 times higher than pristine CdS. It is revealed that the outstanding photocatalytic performance is attributed to the formation of rapid electron transfer channels through the interfacial Cd─O bonding as evidenced by the density functional theory (DFT) calculations and in situ X-ray photoelectron spectroscopy (XPS) analysis. The charge transfer mechanism involved in S-scheme heterojunctions is further investigated through the photo-irradiated Kelvin probe force microscopy (KPFM) analysis. This work provides a new point of view on the mechanism of interfacial charge transfer and points out the direction of designing superior organic-inorganic S-scheme heterojunction photocatalysts.

Molecularly Tunable Heterostructured Co-Polymers Containing Electron-Deficient and -Rich Moieties for Visible-Light and Sacrificial-Agent-Free H2O2 Photosynthesis.

As an alternative to hydrogen peroxide (H2O2) production by complex anthraquinone oxidation process, photosynthesis of H2O2 from water and oxygen without sacrificial agents is highly demanded. Herein, a covalently connected molecular heterostructure is synthesized via sequential C-H arylation and Knoevenagel polymerization reactions for visible-light and sacrificial-agent-free H2O2 synthesis. The subsequent copolymerization of the electron-deficient benzodithiophene-4,8-dione (BTD) and the electron-rich biphenyl (B) and p-phenylenediacetonitrile (CN) not only expands the π-conjugated domain but also increases the molecular dipole moment, which largely promotes the separation and transfer of the photoinduced charge carriers. The optimal heterostructured BTDB-CN0.2 manifested an impressive photocatalytic H2O2 production rate of 1920 µmol g-1 h-1, which is 2.2 and 11.6 times that of BTDB and BTDCN. As revealed by the femtosecond transient absorption (fs-TA) and theoretical calculations, the linkage serves as a channel for the rapid transfer of photogenerated charge carriers, enhancing the photocatalytic efficiency. Further, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) uncovers that the oxygen reduction reaction occurs through the step one-electron pathway and the mutual conversion between C=O and C-OH with the anchoring of H+ during the catalysis favored the formation of H2O2. This work provides a novel perspective for the design of efficient organic photocatalysts.

Atomic Interface Engineering of Single-Atom Pt/TiO2 -Ti3 C2 for Boosting Photocatalytic CO2 Reduction.

Solar-driven CO2 conversion into valuable fuels is a promising strategy to alleviate the energy and environmental issues. However, inefficient charge separation and transfer greatly limits the photocatalytic CO2 reduction efficiency. Herein, single-atom Pt anchored on 3D hierarchical TiO2 -Ti3 C2 with atomic-scale interface engineering is successfully synthesized through an in situ transformation and photoreduction method. The in situ growth of TiO2 on Ti3 C2 nanosheets can not only provide interfacial driving force for the charge transport, but also create an atomic-level charge transfer channel for directional electron migration. Moreover, the single-atom Pt anchored on TiO2 or Ti3 C2 can effectively capture the photogenerated electrons through the atomic interfacial PtO bond with shortened charge migration distance, and simultaneously serve as active sites for CO2 adsorption and activation. Benefiting from the synergistic effect of the atomic interface engineering of single-atom Pt and interfacial TiOTi, the optimized photocatalyst exhibits excellent CO2 -to-CO conversion activity of 20.5 µmol g-1  h-1 with a selectivity of 96%, which is five times that of commercial TiO2 (P25). This work sheds new light on designing ideal atomic-scale interface and single-atom catalysts for efficient solar fuel conversation.

Promoting Solar-driven Hydrogen Peroxide Production over Thiazole-based Conjugated Polymers via Generating and Converting Singlet Oxygen.

Solar-driven synthesis of hydrogen peroxide (H2 O2 ) from water and air provides a low-cost and eco-friendly alternative route to the traditional anthraquinone method. Herein, four thiazole-based conjugated polymers (Tz-CPs: TTz, BTz, TBTz and BBTz) are synthesized via aldimine condensation. BBTz exhibits the highest H2 O2 production rate of 7274 µmol g-1 h-1 in pure water. Further, the reaction path is analyzed by electron paramagnetic resonance (EPR), in situ diffuse reflectance infrared Fourier transform (DRIFT) and theoretical calculation, highlighting the prominent role of singlet oxygen (1 O2 ). The generation of 1 O2 occurs through the oxidation of superoxide radical (⋅O2 - ) and subsequent conversion into endoperoxides via [4+2] cycloaddition over BBTz, which promotes charge separation and reduces the barrier for H2 O2 production. This work provides new insight into the mechanism of photocatalytic O2 reduction and the molecular design of superior single-polymer photocatalysts.

Calcination-regulated Microstructures of Donor-Acceptor Polymers towards Enhanced and Stable Photocatalytic H2 O2 Production in Pure Water.

Regulating molecular structure of donor-acceptor (D-A) polymer is a promising strategy to improve photoactivity. Herein, a porous nanorod-like D-A polymer is synthesized via a strategy of supramolecular chemistry combined with subsequent calcination treatment. This polymer consists of benzene rings (D) and triazine (A) that are linked by amido bond (-CONH-). -CONH- further partially cracks into cyano groups (-C≡N) (A) under calcination. The ratio of benzene to triazine could be tuned to adjust the -C≡N content by varying the calcination atmosphere. Such regulation of molecular structure could modulate the band structure of D-A polymer and endow it with unique porous nanorod-like morphology, leading to the achievement of two-electron oxygen reduction and two-electron water oxidation and the improvement of exciton splitting, O2 adsorption and activation. These merits synergistically ensure a highly efficient and stable photocatalytic H2 O2 production in pure water.

Designing a 0D/2D S-Scheme Heterojunction over Polymeric Carbon Nitride for Visible-Light Photocatalytic Inactivation of Bacteria.

Constructing heterojunctions between two semiconductors with matched band structure is an effective strategy to acquire high-efficiency photocatalysts. The S-scheme heterojunction system has shown great potential in facilitating separation and transfer of photogenerated carriers, as well as acquiring strong photoredox ability. Herein, a 0D/2D S-Scheme heterojunction material involving CeO2 quantum dots and polymeric carbon nitride (CeO2 /PCN) is designed and constructed by in situ wet chemistry with subsequent heat treatment. This S-scheme heterojunction material shows high-efficiency photocatalytic sterilization rate (88.1 %) towards Staphylococcus aureus (S. aureus) under visible-light irradiation (λ≥420 nm), which is 2.7 and 8.2 times that of pure CeO2 (32.2 %) and PCN (10.7 %), respectively. Strong evidence of S-scheme charge transfer path is verified by theoretical calculations, in situ irradiated X-ray photoelectron spectroscopy, and electron paramagnetic resonance.

Size- and shape-dependent catalytic performances of oxidation and reduction reactions on nanocatalysts.

Heterogeneous catalysis is one of the most important chemical processes of various industries performed on catalyst nanoparticles with different sizes or/and shapes. In the past two decades, the catalytic performances of different catalytic reactions on nanoparticles of metals and oxides with well controlled sizes or shapes have been extensively studied thanks to the spectacular advances in syntheses of nanomaterials of metals and oxides. This review discussed the size and shape effects of catalyst particles on catalytic activity and selectivity of reactions performed at solid-gas or solid-liquid interfaces with a purpose of establishing correlations of size- and shape-dependent chemical and structural factors of surface of a catalyst with the corresponding catalytic performances toward understanding of catalysis at a molecular level.

From Millimeter to Subnanometer: Vapor-Solid Deposition of Carbon Nitride Hierarchical Nanostructures Directed by Supramolecular Assembly.

Shape and nanostructure control has great potential to enable graphitic carbon nitride (C3 N4 ) structures with new properties and functionalities. In this work, a new type of hierarchically structured nanoporous C3 N4 is introduced. The C3 N4 exhibits unique, edelweiss-like morphology, with components ranging from millimeter-sized bunches to subnanometer-thick layers. A one-step vapor-solid deposition approach using supramolecular aggregates as the precursor is carried out to accomplish the growth. Supramolecular pre-association plays a crucial role in achieving this nanostructure by directing the vaporization and deposition processes. Furthermore, very small C3 N4 quantum dots can be readily acquired by bath sonication of the thin layers in water. The supramolecular preorganization growth strategy developed herein may provide a general methodology in the design of advanced photoelectric materials with broad applications in energy conversion and storage.

Shape-dependent photocatalytic hydrogen evolution activity over a Pt nanoparticle coupled g-C3N4 photocatalyst.

Cubic, octahedral and spherical platinum (Pt) nanoparticles (NPs) ex situ supported on a graphitic carbon nitride (g-C3N4) substrate are synthesized using a colloidal adsorption-deposition method for photocatalytic hydrogen evolution reactions. These Pt NPs of different shapes have similar sizes of around 10 nm but have different facets exposed. It is found that the visible-light-driven photocatalytic activities for the Pt/g-C3N4 hybrid photocatalysts follow the order as: cubic Pt/g-C3N4 < octahedral Pt/g-C3N4 < spherical Pt/g-C3N4, revealing the significant cocatalyst shape-sensitive photocatalytic activity in the Pt/g-C3N4 hybrids. This is mainly due to the different surface atomic structures of different exposed facets of Pt NPs, which lead to the disparity of active sites and adsorption energies in photocatalytic reactions.

Efficient CO2 capture and photoreduction by amine-functionalized TiO2.

Amine-functionalization of TiO2 nanoparticles, through a solvothermal approach, substantially increases the affinity of CO2 on TiO2 surfaces through chemisorption. This chemisorption allows for more effective activation of CO2 and charge transfer from excited TiO2 , and significantly enhances the photocatalytic rate of CO2 reduction into methane and CO.

Rational synthesis of triangular Au-Ag(2)S hybrid nanoframes with effective photoresponses.

Triangular Au­Ag2S hybrid nanoframes were successfully synthesised by using Ag nanoprisms as templates through gold coating, etching and sulfuration. These Au­Ag2S hybrid nanoframes exhibit effective photocurrent responses for potential photoelectrochemical applications.

Surfactant-free sub-2 nm ultrathin triangular gold nanoframes.

Ultrathin triangular gold nanoframes are synthesized in high yield through selective gold deposition on the edges of triangular silver nanoprisms and subsequent silver etching with mild wet etchants. These ultrathin gold nanoframes are surfactant-free with tailorable ridge thickness from 1.8 to 6 nm and exhibit adjustable and distinct surface plasmon resonance bands in the visible and near-IR region. In comparison, etching of the nanoprism template by galvanic replacement can only create frame structures with much thicker ridges, which have much lower catalytic activity for 4-nitrophenol reduction than the ultrathin gold nanoframes.

Artificial photosynthetic hydrogen evolution over g-C3N4 nanosheets coupled with cobaloxime.

We report an economic and noble-metal-free artificial photosynthetic system, consisting of g-C3N4 as a photosensitizer and a photocatalyst, and cobaloxime as a co-catalyst, for H2 generation. This system allows for effective electron transfer from excited g-C3N4 to Co(III)(dmgH)2pyCl to generate reduced cobaloxime intermediate species for efficient H2 evolution. Transient fluorescence studies reveal that the presence of cobaloxime and TEOA promotes the population of excited electrons to transfer from g-C3N4, which is responsible for the high photocatalytic activity of this g-C3N4-cobaloxime conjugation system.

Pore Perforation of Graphene Coupled with In Situ Growth of Co3 Se4 for High-Performance Na-Ion Battery.

Graphene-based nanomaterials have sprung up as promising anode materials for sodium-ion batteries due to the intriguing properties of graphene itself and the synergic effect between graphene and active materials. However, the 2D graphene sheet only allows the rapid diffusion of sodium ions along the parallel direction while that of the vertical direction is difficult, limiting the rate capability of graphene-based electrode materials. To tackle this problem, pore-forming engineering has been employed to perforate graphene and concurrently achieve the in situ growth of Co3 Se4 nanoparticles. The generation of in-plane nanohole breaks through the physical barriers of the graphene nanosheets, enabling the fast diffusion of electrolyte ions in the longitudinal direction. In addition, this design limits the aggregation of Co3 Se4 nanoparticles because of the high affinity of Co3 Se4 on graphene. Benefiting from the high conductivity and fast ion transport bestowed by the ingenious architecture, the Co3 Se4 /holey graphene exhibits a remarkable rate performance of 519.5 mAh g-1 at 5.0 A g-1 and desirable cycle stability. Conclusions drawn from this investigation are that the transport of sodium inside the graphene-based composites is crucial for rate performance enhancement and this method is effective in modifying graphene-based nanomaterials as potential anode materials.

Bioinspired Strategy for Efficient TiO2/Au/CdS Photocatalysts Based On Mesocrystal Superstructures in Biominerals and Charge-Transfer Pathway in Natural Photosynthesis.

Natural photosynthesis involves an efficient charge-transfer pathway through exquisitely arranged photosystems and electron transport intermediates, which separate photogenerated carriers to realize high quantum efficiency. It inspires a rational design construction of artificial photosynthesis systems and the architectures of semiconductors are essential to achieve optimal performance. Of note, biomineralization processes could form various mesocrystals with well-ordered superstructures for unique optical applications. Inspired by both natural photosynthesis and biomineralization, we construct a ternary superstructure-based mesocrystal TiO2 (meso-TiO2)/Au/CdS artificial photosynthesis system by a green photo-assisted method. The well-ordered superstructure of meso-TiO2 and efficient charge-transfer pathway among the three components are crucial for retarding charge recombination. As a result, the meso-TiO2/Au/CdS photocatalyst displays enhanced visible light-driven photocatalytic hydrogen evolution (4.60 mmol h-1 g-1), which is 3.2 times higher than that of commercial TiO2 (P25)/Au/CdS with disordered TiO2 nanocrystal aggregates (1.41 mmol h-1 g-1). This work provides a promising bioinspired design strategy for photocatalysts with an improved solar conversion efficiency.

Alkyl group-decorated g-C3N4 for enhanced gas-phase CO2 photoreduction.

With excellent physical/chemical stability and feasible synthesis, g-C3N4 has attracted much attention in the field of photocatalysis. However, its weak photoactivity limits its practical applications. Herein, by easily planting hydrophobic alkyl groups onto g-C3N4, the hydrophilicity of g-C3N4 can be well regulated and its specific surface area be enlarged simultaneously. Such a modification ensures enhanced CO2 capture and increased active sites. In addition, the introduction of alkyl groups endows g-C3N4 with abundant charge density and efficient separation of photoinduced excitons. All these advantages synergistically contribute to the enhanced photocatalytic CO2 reduction performance over the optimized catalyst (DCN90), and the total CO2 conversion is 7.4-fold that of pristine g-C3N4 (CN).

Calcium phosphate drug nanocarriers with ultrahigh and adjustable drug-loading capacity: One-step synthesis, in situ drug loading and prolonged drug release.

Calcium phosphates (CPs) are regarded as the most biocompatible inorganic biomaterials; however, they are limited in the drug-delivery applications, especially for hydrophobic drugs. Achieving high drug-loading capacity and a controllable drug-release property are two main challenges. In this study we report a strategy for the preparation of novel drug delivery systems based on a concerted process in which the formation of the CP nanocarriers and the drug storage are accomplished in one step in mixed solvents of water and ethanol. The key advantage of this strategy is that the formation of CP nanocarriers and in situ loading of the drug occur simultaneously in the same reaction system, which makes it possible to achieve ultrahigh drug-loading capacity and prolonged drug release due to ultrahigh specific surface area and numerous binding sites of the CP nanocarriers. A series of hydrophobic drug-delivery systems with adjustable drug-loading capacities and drug-release rates have been successfully synthesized. In addition, the drug-release kinetics of the as-prepared drug-delivery systems have been found in which the cumulative amount of drug release has a linear relationship with the natural logarithm of release time. FROM THE CLINICAL EDITOR: Calcium phosphates (CPs) are highly biocompatible inorganic biomaterials with thus far limited drug-delivery applications. This study reports the preparation of a novel drug delivery system where the formation of CP nanocarriers and in situ loading of the drug occur simultaneously in the same reaction, enabling ultra-high drug-loading.

An Inorganic/Organic S-Scheme Heterojunction H2 -Production Photocatalyst and its Charge Transfer Mechanism.

Inspired by natural photosynthesis, constructing inorganic/organic heterojunctions is regarded as an effective strategy to design high-efficiency photocatalysts. Herein, a step (S)-scheme heterojunction photocatalyst is prepared by in situ growth of an inorganic semiconductor firmly on an organic semiconductor. A new pyrene-based conjugated polymer, pyrene-alt-triphenylamine (PT), is synthesized via the typical Suzuki-Miyaura reactions, and then employed as a substrate to anchor CdS nanocrystals. The optimized CdS/PT composite, coupling 2 wt% PT with CdS, exhibits a robust H2 evolution rate of 9.28 mmol h-1 g-1 with continuous release of H2 bubbles, as well as a high apparent quantum efficiency of 24.3%, which is ≈8 times that of pure CdS. The S-scheme charge transfer mechanism between PT and CdS, is systematically demonstrated by photoirradiated Kelvin probe measurement and in situ irradiated X-ray photoelectron spectroscopy analyses. This work provides a protocol for preparing specific S-scheme heterojunction photocatalysts on the basis of inorganic/organic coupling.

Light-driven directional ion transport for enhanced osmotic energy harvesting.

Light-driven ion (proton) transport is a crucial process both for photosynthesis of green plants and solar energy harvesting of some archaea. Here, we describe use of a TiO2/C3N4 semiconductor heterojunction nanotube membrane to realize similar light-driven directional ion transport performance to that of biological systems. This heterojunction system can be fabricated by two simple deposition steps. Under unilateral illumination, the TiO2/C3N4 heterojunction nanotube membrane can generate a photocurrent of about 9 µA/cm2, corresponding to a pumping stream of ∼5500 ions per second per nanotube. By changing the position of TiO2 and C3N4, a reverse equivalent ionic current can also be realized. Directional transport of photogenerated electrons and holes results in a transmembrane potential, which is the basis of the light-driven ion transport phenomenon. As a proof of concept, we also show that this system can be used for enhanced osmotic energy generation. The artificial light-driven ion transport system proposed here offers a further step forward on the roadmap for development of ionic photoelectric conversion and integration into other applications, for example water desalination.

A New Conducting Polymer with Exceptional Visible-Light Photocatalytic Activity Derived from Barbituric Acid Polycondensation.

A novel covalent, metal-free, photocatalytic material is prepared by thermal polymerization of barbituric acid (BA). The structure of the photocatalyst is analyzed by using scanning electron microscopy, X-ray diffraction, and infrared, UV-visible, and 1 H solution and 13 C solid-state NMR spectroscopy. The photodegradation efficiency of BA thermally polymerized at different temperatures is tested by photocatalytic degradation of aquatic rhodamine B (RhB) dye under visible-light irradiation. It is shown that heating BA at an optimized temperature of 300 °C, that is, still in the range that polymer-like polycondensation takes place, results in a photocatalyst that can remove RhB with 96% photodegradation efficiency after 70 min exposure to visible light. The polycondensation reaction of BA is identified to process through precipitation of trimer units as primary building blocks. Reference experiments such as addition of scavengers and saturation with oxygen are studied to understand the photodegradation process. It is shown that the presence of triethanolamine, and excess of oxygen and p-benzoquinone in the solution of RhB and photocatalyst (BA300) is not beneficial, but decreases the photodegradation efficiency.