Concentrated solar CO2 reduction in H2O vapour with >1% energy conversion efficiency.

H2O dissociation plays a crucial role in solar-driven catalytic CO2 methanation, demanding high temperature even for solar-to-chemical conversion efficiencies <1% with modest product selectivity. Herein, we report an oxygen-vacancy (Vo) rich CeO2 catalyst with single-atom Ni anchored around its surface Vo sites by replacing Ce atoms to promote H2O dissociation and achieve effective photothermal CO2 reduction under concentrated light irradiation. The high photon flux reduces the apparent activation energy for CH4 production and prevents Vo from depletion. The defects coordinated with single-atom Ni, significantly promote the capture of charges and local phonons at the Ni d-impurity orbitals, thereby inducing more effective H2O activation. The catalyst presents a CH4 yield of 192.75 µmol/cm2/h, with a solar-to-chemical efficiency of 1.14% and a selectivity ~100%. The mechanistic insights uncovered in this study should help further the development of H2O-activating catalysts for CO2 reduction and thereby expedite the practical utilization of solar-to-chemical technologies.

Integration of Co Single Atoms and Ni Clusters on Defect-Rich ZrO2 for Strong Photothermal Coupling Boosts Photocatalytic CO2 Reduction.

We report a solvothermal method for the synthesis of an oxygen vacancy-enriched ZrO2 photocatalyst with Co single atoms and Ni clusters immobilized on the surface. This catalyst presents superior performance for the reduction of CO2 in H2O vapor, with a CO yield reaching 663.84 µmol g-1 h-1 and a selectivity of 99.52%. The total solar-to-chemical energy conversion efficiency is up to 0.372‰, which is among the highest reported values. The success, on one hand, depends on the Co single atoms and Ni clusters for both extended spectrum absorption and serving as dual-active centers for CO2 reduction and H2O dissociation, respectively; on the other hand, this is attributed to the enhanced photoelectric and thermal effect induced by concentrated solar irradiation. We demonstrate that an intermediate impurity state is formed by the hybridization of the d-orbital of single-atom Co with the molecular orbital of H2O, enabling visible-light-driven excitation over the catalyst. In addition, Ni clusters play a crucial role in altering the adsorption configuration of CO2, with the localized surface plasmon resonance effect enhancing the activation and dissociation of CO2 induced by visible-near-infrared light. This study provides valuable insights into the synergistic effect of the dual cocatalyst toward both efficient photothermal coupling and surface redox reactions for solar CO2 reduction.

Regulating Lewis Acidic Sites of 1T-2H MoS2 Catalysts for Solar-Driven Photothermal Catalytic H2 Production from Lignocellulosic Biomass.

Solar-driven photothermal catalytic H2 production from lignocellulosic biomass was achieved by using 1T-2H MoS2 with tunable Lewis acidic sites as catalysts in an alkaline aqueous solution, in which the number of Lewis acidic sites derived from the exposed Mo edges of MoS2 was successfully regulated by both the formation of an edge-terminated 1T-2H phase structure and tunable layer number. Owing to the abundant Lewis acidic sites for the oxygenolysis of lignocellulosic biomass, the 1T-2H MoS2 catalyst shows high photothermal catalytic lignocellulosic biomass-to-H2 transformation performance in polar wood chips, bamboo, rice straw corncobs, and rice hull aqueous solutions, and the highest H2 generation rate and solar-to-H2 (STH) efficiency respectively achieves 3661 µmol·h-1·g-1 and 0.18% in the polar wood chip system under 300 W Xe lamp illumination. This study provides a sustainable and cost-effective method for the direct transformation of renewable lignocellulosic biomass to H2 fuel driven by solar energy.

Photothermally driven decoupling of gas evolution at the solid-liquid interface for boosted photocatalytic hydrogen production.

The slow mass transfer, especially the gas evolution process at the solid-liquid interface in photocatalytic water splitting, restricts the overall efficiency of the hydrogen evolution reaction. Here, we report a novel gas-solid photocatalytic reaction system by decoupling hydrogen generation from a traditional solid-liquid interface. The success relies on annealing commercial melamine sponge (AMS) for effective photothermal conversion that leads to rapid water evaporation. The vapor flows towards the photocatalyst covering the surface of the AMS and is split by the catalyst therein. This liquid-gas/gas-solid coupling system avoids the formation of photocatalytic bubbles at the solid-liquid interface, leading to significantly improved mass transfer and conversion. Utilizing CdS nanorods anchored by highly dispersed nickel atoms/clusters as a model photocatalyst, the highest hydrogen evolution rate from water splitting reaches 686.39 µmol h-1, which is 5.31 times that of the traditional solid-liquid-gas triphase system. The solar-to-hydrogen (STH) efficiency can be up to 2.06%. This study provides a new idea for the design and construction of efficient practical photocatalytic systems.

Fermi Level Pinning in Concentrated Light-Induced Band Edge Tuning Maximizes Photocatalytic Solar-to-Hydrogen Efficiency.

Here, we demonstrate a concentrated light-induced band edge tuning effect in photocatalytic hydrogen production. This band movement along with Femi level pinning leads to two distinct catalytic behaviors upon irradiation flux increase. Specifically, the concentration of the light promotes more long-lived carriers bound to the surface electronic states, progressively boosting energy conversion efficiency to a maximum value. Afterward, efficiency diminishes gradually due to poor carrier transfer. This work offers critical insights into efficient and economical photocatalytic hydrogen production.

Boosting photocatalytic degradation of tetracycline under visible light over hierarchical carbon nitride microrods with carbon vacancies.

Graphitic carbon nitride is considered as one of the promising photocatalysts for pollution elimination from wastewater. Manipulating the microstructure of carbon nitride remains a challengeable task, which is essential for improving light absorption, separating photogenerated carrier and creating reactive sites. Herein, a carbon vacancy modified hierarchical carbon nitride microrod (CN1.5) has been prepared templated from a melamine-NH2OH·HCl complex. The hierarchical microrods are demonstrated to be comprised of interconnected nanosheets with rich carbon vacancies, which endows it with high specific surface area, enhanced light utilization efficiency, available reactive sites, improved charge carrier separation and numerous mass-transport channels. The resultant photocatalyst CN1.5 exhibits an excellent photodegradation efficiency of 87.9% towards tetracycline under visible light irradiation. The remarkable apparent rate constant of 4.91 × 10-2 min-1 is 7.3 times higher than that of bulk CN. In addition, the degradation pathways are deduced base on the observation of degradation intermediates generating in the photocatalytic process. Mechanism investigation indicates that the major contribution for photodegradation is attributed to ·O2-, 1O2 and H2O2 species. This work provides new insights into advancing carbon nitride's microstructure to improve photocatalytic degradation performance for highly efficient antibiotic removal and environment remediation.

One-Pot Hydrothermal Synthesis of MoS2/Zn0.5Cd0.5S Heterojunction for Enhanced Photocatalytic H2 Production.

A series of molybdenum disulfide (MoS2)/Zn0.5Cd0.5S heterojunctions have been prepared via a mild one-pot hydrothermal method based on the optimization of composition content of primary photocatalyst. The photocatalysts demonstrated significantly improved visible light-driven photocatalytic activity toward H2 evolution from water without using any noble metal cocatalyst. Among the as-prepared composites, 0.2% MoS2/Zn0.5Cd0.5S shows the best performance. The highest H2 evolution rate reaches 21 mmol · g-1 · h-1, which is four times higher than that of pure Zn0.5Cd0.5S. The apparent quantum efficiency is about 46.3% at 425 nm. The superiority is attributed to the tight connection between MoS2 and Zn0.5Cd0.5S by this facile one-step hydrothermal synthesis. As a result, the formation of the heterostructure introduces built-in electric field at the interface that facilitates vectorial charge transfer. More specifically, photogenerated electrons transfer to MoS2 to conduct proton reduction, where the holes are retained on the surface of Zn0.5Cd0.5S to react with the sacrificial reagents. Moreover, the composite presents improved stability without notable activity decay after several cycled tests.

Integration of CdS particles into sodium alginate aerogel with enhanced photocatalytic performance.

In the present work, CdS nanoparticles were integrated into sodium alginate aerogel matrix through a facile method. The CdS particles were successfully incorporated into the network of sodium alginate and highly distributed. Moreover, the accessibility of pore structures of sodium alginate was well-preserved. The resulting hybrid aerogels demonstrated high photocatalytic ability towards Cr (VI) reduction. SA/CdS-2 (mass ratio SA: CdS = 1:2) exhibited the highest reduction efficiency of Cr (VI), which could reduce the concentration of Cr (VI) to 0 mg/L after 60 min illumination. A probably adsorption-photoreduction mechanism was proposed and discussed in detail. The aerogels had excellent reusability and recyclability, avoiding secondary pollution. This work holds a promise to design and fabrication of CdS particles into three-dimensional aerogel network.

Effect of the surface acid sites of tungsten trioxide for highly selective hydrogenation of cellulose to ethylene glycol.

This work studied a facile and template-free hydrothermal route for controlled synthesis of tungsten trioxide in the form of hexagonal nanorod (h-WO3) and monoclinic nanosheet (m-WO3). The surface morphology, crystal plane, surface bound water, and surface acid sites of the two kinds of WO3 nanocrystals were investigated systematically. They were further evaluated as catalysts for selective cellulose hydrolysis. While both of them exhibited good catalytic performance, h-WO3 was found to be more preferential for ethylene glycol (EG) generation. This catalytic performance relied on both the unique active crystal surface (1 0 0) and surface binding water (WO3-H2O) formed by h-WO3 crystals, which provided more Lewis acid sites for degrading cellulose into EG. Results showed that the highest EG yield reaches 77.5% by a combination of loading 1 wt% Ru on the h-WO3 catalyst.

Hybrid BiOBr/UiO-66-NH2 composite with enhanced visible-light driven photocatalytic activity toward RhB dye degradation.

Metal-organic framework (MOFs) based composites have received more research interest for photocatalytic applications during recent years. In this work, a highly active, visible light photocatalyst BiOBr/UiO-66-NH2 hybrid composite was successfully prepared by introducing various amounts of UiO-66-NH2 with BiOBr through a co-precipitation method. The composites were applied for the photocatalytic degradation of RhB (rhodamine B) dye. The developed BiOBr/UiO-66-NH2 composites exhibited higher photocatalytic activity than the pristine material. In RhB degradation experiments the hybrid composite with 15 wt% of UiO-66-NH2 shows degradation efficiency conversion of 83% within two hours under visible light irradiation. The high photodegradation efficiency of BUN-15 could be ascribed to efficient interfacial charge transfer at the heterojunction and the synergistic effect between BiOBr/UiO-66-NH2. In addition, an active species trapping experiment confirmed that photo-generated hole+ and O2 - radicals are the major species involved in RhB degradation under visible light.

Photochromic Inorganic/Organic Thermoplastic Elastomers.

Photochromic materials are an important class of "smart materials" and are broadly utilized in technological devices. However, most photochromic materials reported so far are composed of inorganic compounds that are challenging to process and suffer from poor mechanical performance, severely limiting their applications in various markets. In this paper, inorganic photochromic tungsten trioxide (WO3 ) nanocrystals are conveniently grafted with polymers to hurdle the deficiency in processability and mechanical properties. This new type of photochromic material can be thermally processed into desired geometries like disks and dog-bone specimens. Fully reversible photochromic response under UV light is also achieved for WO3 -graft polymers, exhibiting tunable response rate, outperforming the pristine WO3 nanocrystals. Notably, the resulted graft polymers show extraordinary mechanical performance with excellent ductility (≈800% breaking strain) and relatively high breaking strength (≈2 MPa). These discoveries elucidate an effective pathway to design smart inorganic/organic hybrid thermoplastic elastomers endowed with outstanding photochromic and mechanical properties as well as exceptional processability.

Charge separation in facet-engineered chalcogenide photocatalyst: a selective photocorrosion approach.

Finding active sites for photocatalytic reduction and oxidation allows the mechanistic understanding of a given reaction, ensuring the rational design and fabrication of an efficient photocatalyst. Herein, using well-shaped Cu2WS4 decahedra as model photocatalysts, we demonstrated that photoinduced oxidative etching could be considered as an indication of the photooxidation reaction sites of chalcogenide photocatalyst as it only occurred on {101} facets of Cu2WS4 during photocatalytic hydrogen production. The photocatalytic reduction reaction, in contrast, was confined on its {001} facets. Based on this finding, the photocatalytic activity of Cu2WS4 decahedra could be further tailored by controlling the ratio of {001}/{101} facets. Thus, this work provides a general route to the determination of reactive sites on shaped chalcogenide photocatalysts.

Localized nano-solid-solution induced by Cu doping in ZnS for efficient solar hydrogen generation.

Nanosized photocatalysts have been shown to be important to many modern photocatalytic reactions. Control of the microstructure of the nanocrystals enables regulation of their optical properties and enhancement of specific reactions. Here, Cu(2+)-doped ZnS nanosphere photocatalysts with hierarchical nanostructures and controllable sizes were synthesized via a facile wet-chemical reaction. We demonstrated that small amounts of Cu(2+) doping could give rise to the formation of a variety of localized, nanosized Cu(1-x)Zn(x)S solid solutions that are separated by a continuous ZnS medium. The nano-solid-solutions have predictable band structures and an average size of several nanometers, which ensure facile generation of electron-hole pairs by visible light irradiation and quick migration of the photo-generated charges to the interfaces. With Ru as a cocatalyst, the as-prepared 0.5 mol% Cu(2+)-doped ZnS nanospheres showed a high H2 evolution rate of 1.03 mmol h(-1), corresponding to a quantum efficiency of 26.2% at 425 nm. A hierarchical surface structure with a large surface area is considered crucial for the increased activity. Our work not only showed that the non-toxic metal chalcogenides achieve high efficiency but also provides a new concept of localized nano-solid-solution for photocatalytic applications.

Structural and luminescence properties of Y(2-x)GeMoO8:REx (RE = Eu, Tb) phosphors.

Y(2-x)GeMoO8:REx (RE = Eu, Tb) phosphors were synthesized using a facile sol-gel method. The morphology and structure of the phosphors were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD); while their luminescent properties were investigated by photoluminescence (PL) spectrometry. Our results reveal that all of these Y(2-x)GeMoO8:REx (RE = Eu, Tb) phosphors adopted the tetragonal phase, belonging to Scheelite (CaWO4 ) structure. The obtained YGeMoO8:Eu phosphors exhibit a strong emission in the red light range which can be assigned to the (5)D0 → (7)F2 transition of Eu(3+) when it is excited at 459 nm. Under 392 and 489 nm excitation, the YGeMoO8:Tb phosphors present predominant green emission ((5)D4 → (7)F5) at 540 nm. The highest emission of the phosphors can be achieved by adjusting the doping concentration to be 0.25 for Eu(3+) and 0.15 for Tb(3+), respectively. The promising luminescence properties of these materials indicate that they can be potentially applied to white-light-emitting diodes.

Facile synthesis of Pd-Ir bimetallic octapods and nanocages through galvanic replacement and co-reduction, and their use for hydrazine decomposition.

This article describes a facile synthesis of Pd-Ir bimetallic nanostructures in the forms of core-shell octapods and alloyed nanocages. The success of this synthesis relies on the use of Pd nanocubes as the sacrificial templates and interplay of two different processes: the galvanic replacement between an Ir precursor and the Pd nanocubes and the co-reduction of Pd(2+) and Ir(3+) by ethylene glycol. The galvanic replacement played a dominant role in the initial stage, through which Pd atoms were dissolved from the side faces whereas Ir atoms were deposited at the corner sites to generate Pd-Ir core-shell octapods. As the concentration of Pd(2+) in the reaction mixture was increased, co-reduction of Pd(2+) and Ir(3+) occurred in the late stage of synthesis. The resultant Pd and Ir atoms were deposited onto the octapods while the Pd atoms in the interiors continued to be etched away due to the galvanic replacement, finally leading to the formation of Pd-Ir alloyed nanocages. The octapods and nanocages were then evaluated as catalysts for the selective generation of hydrogen from the decomposition of hydrous hydrazine. The nanocages exhibited better selectivity for hydrogen generation than octapods (66% versus 29%), which can be attributed to the presence of an alloyed, porous structure on the surface.

Synthesis of Ag nanobars in the presence of single-crystal seeds and a bromide compound, and their surface-enhanced Raman scattering (SERS) properties.

This Article describes the synthesis of Ag nanobars with different aspect ratios using a seed-mediated method and evaluation of their use for surface-enhanced Raman scattering (SERS). The formation of Ag nanobars was found to critically depend on the introduction of a bromide compound into the reaction system, with ionic salts being more effective than covalent molecules. We examined single-crystal seeds with both spherical and cubic shapes and found that Ag nanobars grown from spherical seeds had much higher aspect ratios than those grown from cubic seeds. The typical product of a synthesis contained nanocrystals with three different morphologies: nanocubes, nanobars with a square cross section, and nanobars with a rectangular cross section. Their formation can be attributed to the difference in growth rates along the three orthogonal <100> directions. The SERS enhancement factor of the Ag nanobar was found to depend on its aspect ratio, its orientation relative to the laser polarization, and the wavelength of excitation.

(E)-2-[(5-Bromo-2-hydroxy-benzyl-idene)amino]benzonitrile.

In the mol-ecule of the title compound, C(14)H(9)BrN(2)O, the dihedral angle between the aromatic rings is 1.09 (4)°. Intra-molecular O-H⋯N hydrogen bonding results in the formation of a planar (r.m.s. deviation = 0.0140 Å) six-membered ring. In the crystal structure, inter-molecular C-H⋯N inter-actions link the mol-ecules into chains.

(E)-3-(2-Hydr-oxy-3-methoxy-benzyl-idene-amino)benzonitrile.

The mol-ecule of the title compound, C(15)H(12)N(2)O(2), displays a trans configuration with respect to the C=N double bond. The dihedral angle between the two benzene rings is 30.46 (14)°. A strong intra-molecular O-H⋯O hydrogen bond stabilizes the mol-ecular structure.

1-(4-tert-Butyl-benz-yl)-2-(4-tert-butyl-phen-yl)-1H-benzimidazole.

In the mol-ecule of the title compound, C(28)H(32)N(2), the benzimidazole ring system is almost planar [maximum deviation = 0.0221 (15) Å] and forms dihedral angles of 85.86 (4) and 32.09 (6)° with the benzene rings. In the crystal structure, mol-ecules are linked into chains running parallel to the a axis by inter-molecular C-H⋯N hydrogen bonds. The methyl groups of a tert-butyl group are rotationally disordered over two positions with refined site-occupancy factors of 0.636 (4) and 0.364 (4).