A plasma oxidation method is developed to fabricate atomic‐scale pores in the basal planes of electrochemically inert TaS2 nanosheets to functionalize the 2D crystals with high electrocatalysis for ...hydrogen evolution reaction. Quantitative measurements of under‐coordinated atoms at edges of the pores by aberration‐corrected transmission electron microscopy reveal the intrinsic correlation between the defective atomic sites and electrocatalytic activities of 2D TaS2.
A novel architecture of 3D graphene growth on porous Al2O3 ceramics is proposed for thermal management using ambient pressure chemical vapor deposition. The formation mechanism of graphene is ...attributed to the carbothermic reduction occurring at the Al2O3 surface to initialize the nucleation and growth of graphene. The graphene films are coated on insulating anodic aluminum oxide (AAO) templates and porous Al2O3 ceramic substrates. The graphene coated AAO possesses one‐dimensional isolated graphene tubes, which can act as the media for directional thermal transport. The graphene/Al2O3 composite (G‐Al2O3) contains an interconnected macroporous graphene framework with an extremely low sheet electrical resistance down to 0.11 Ω sq−1 and thermal conductivity with 8.28 W m−1 K−1. The G‐Al2O3 provides enormous conductive pathways for electronic and heat transfer, suitable for application as heat sinks. Such a porous composite is also attractive as a highly thermally conductive reservoir to hold phase change materials (stearic acid) for thermal energy storage. This work displays the great potential of CVD direct growth of graphene on dielectric porous substrates for thermal conduction and electronic applications.
A novel architecture of 3D graphene is proposed by direct growth on porous Al2O3 ceramics by using chemical vapor deposition. The graphene/Al2O3 composite provides enormous conductive pathways for electron and phonon transport, suitable for application as a heat sink. Furthermore, the composite acts as a new type of highly thermally conductive reservoir to accommodate phase change materials for thermal energy storage.
Extraordinary tubular graphene cellular material of a tetrahedrally connected covalent structure was very recently discovered as a new supermaterial with ultralight, ultrastiff, superelastic, and ...excellent conductive characteristics, but no high specific surface area will keep it from any next-generation energy storage applications. Herein, we prepare another new graphene monolith of mesoporous graphene-filled tubes instead of hollow tubes in the reported cellular structure. This graphene nanoporous monolith is also composed of covalently bonded carbon network possessing high specific surface area of ∼1590 m2 g–1 and electrical conductivity of ∼32 S cm–1, superior to graphene aerogels and porous graphene forms self-assembled by graphene oxide. This 3D graphene monolith can support over 10 000 times its own weight, significantly superior to CNT and graphene cellular materials with a similar density. Furthermore, pseudocapacitance-active functional groups are introduced into the new nanoporous graphene monolith as an electrode material in electrochemical capacitors. Surprisingly, the electrode of 3D mesoporous graphene has a specific capacitance of 303 F g–1 and maintains over 98% retention after 10 000 cycles, belonging to the list for the best carbon-based active materials. The macroscopic mesoporous graphene monolith suggests the great potential as an electrode for supercapacitors in energy storage areas.
Well‐crystallized Nb‐doped anatase TiO2 nanoparticles are prepared by a novel synthetic route and successfully used as the photoanode of dye‐sensitized solar cells (DSSCs). The homogenous ...distribution of Nb in the TiO2 lattice is confirmed by scanning transmission electron microscopy (STEM) elemental mapping and line‐scanning analyses. After Nb doping, the conductivity of the TiO2 powder increases, and its flat‐band potential (Vfb) has a positive shift. The energy‐conversion efficiency of a cell based on 5.0 mol% Nb‐doped TiO2 is significantly better, by about 18.2%, compared to that of a cell based on undoped TiO2. The as‐prepared Nb‐doped TiO2 material is proven in detail to be a better photoanode material than pure TiO2, and this new synthetic approach using a water‐soluble precursor provides a simple and versatile way to prepare excellent photoanode materials.
Well‐crystallized Nb‐doped anatase TiO2 nanoparticles are prepared by a novel synthetic route and used as the photoanode of dye‐sensitized solar cells. The homogenous distribution of Nb in the TiO2 lattice is confirmed by STEM analysis. The energy conversion efficiency is improved by 18.2% after Nb‐doping, and the as‐prepared Nb‐doped TiO2 is proved in detail to be a better photoanode material than pure TiO2 (see figure).
Mesoporous phosphated TiO2 (PTO) exhibits high SSA, narrow pore size distribution, low pHzpc value and abundant surface hydroxy group was prepared through co-precipitation methord in boiling water ...process. Addtionally, the as-prepared mesoporous 8-PTO adsorbent possesses an excellent adsorption capacity of Cr(III) without significant degradation after five consecutive cycles.
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•Mesoporous phosphated TiO2 (PTO) was successfully synthesized in boiling water.•The optimized 8-PTO exhibits superior Cr (III) adsorption up to 92 mg/g in sewage.•PO4 tetrahedral incorporation into the network of TiO6 octahedral can effectively introduce hydroxyl groups.•Hydroxyl groups play a decisive role in the adsorption process.
Heavy metal removal by environmental-friendly nanostructured TiO2 adsorbent is a promising strategy to facilitate wastewater treatment. Here, a boiling water synthetic approach is explored to prepare mesoporous phosphated TiO2 (PTO) used for Cr(III) adsorption in polluted water. We obtain mesoporous 8-PTO (synthesized with 8% molar ratio of H3PO4) with a high specific surface area (278 m2/g), narrow size distribution (<5 nm), low pHzpc (pH of zero point of charge) value (∼1.0), and abundant surface hydroxyl group, which is attributed to the introduction of H3PO4 during the hydrolysis process of TiCl4 in boiling water. Importantly, the obtained 8-PTO shows better thermal stability than pure TiO2 and retains mesoporous structure after thermal treatment owning to PO4 tetrahedral incorporated into the network of TiO6 octahedral. The optimized 8-PTO exhibits superior Cr(III) adsorption up to 92 mg/g in sewage, which makes it one of the best materials among TiO2 adsorbent known for Cr(III) Removal (10–83 mg/g). Additionally, the as-prepared mesoporous 8-PTO adsorbent possesses an excellent reusability without significant degradation and can largely avoid the generation of secondary contaminants. A linear relationship (R2 = 0.9985) between adsorption capacity and hydroxyl content percentage of different PTO samples is revealed, indicating that the surface hydroxyl groups play a decisive role in the adsorption process. This study provides a facile approach to synthesize high specific surface area mesoporous phosphated TiO2 with rich surface functional groups for efficient Cr(III) removal in sewage.
Modification of rutile titanium dioxide (TiO2) for hydrogen generation and water cleaning is a grand challenge due to the chemical inertness of rutile, while such inertness is a desired merit for its ...stability in photoelectrochemical applications. Herein, we report an innovative two-step method to prepare a core–shell nanostructured S-doped rutile TiO2 (R′-TiO2-S). This modified black rutile TiO2 sample exhibits remarkably enhanced absorption in visible and near-infrared regions and efficient charge separation and transport. As a result, the unique sulfide surface (TiO2–x :S) boosts the photocatalytic water cleaning and water splitting with a steady solar hydrogen production rate of 0.258 mmol h–1 g–1. The black titania is also an excellent photoelectrochemical electrode exhibiting a high solar-to-hydrogen conversion efficiency of 1.67%. The sulfided surface shell is proved to be an effective strategy for enhancing solar light absorption and photoelectric conversion.
A phase change material consisting of three-dimensional graphene aerogel (GA) and octadecanoic acid (OA) was produced. The GA was assembled from the sheets of graphene oxide in a hydrothermal ...reaction. The pore sizes of the network were several micrometers and the pore walls consisted of thin layers of stacked graphene sheets. OA was impregnated into GA by capillary forces, with the GA acting as the support. The GA/OA composite had a thermal conductivity about 2.635W/mK at a GA loading fraction of ∼20vol%, which was about 14 times that of the OA (0.184W/mK). The transient heating and cooling responses of the material were investigated for thermal energy storage. The GA had a low bulk density so that the weight percent of the GA in the composite was only about 15%. The composite presents a high heat storage capacity of 181.8J/g, which was very close to the value of the OA alone (186.1J/g).
► A phase change material consisting of three-dimensional graphene aerogel and octadecanoic acid was produced for thermal energy storage. ► The material had a thermal conductivity of about 2.635W/mK, which was about 14 times that of the octadecanoic acid (0.184W/mK). ► The material presents a high heat storage capacity of 181.8J/g, which was very close to the value of the octadecanoic acid alone (186.1J/g).
With the addition of oxygen into the chain-like bismuth sulfide of Bi2S3, there are two interesting functional compounds of Bi2O2S (photoelectric) and Bi4O4S3 (superconducting) containing the ...PbO-like Bi2O2 layers. Nanoscale Bi2O2S crystals with an indirect band gap of 1.12 eV are synthesized via a facile hydrothermal method. This semiconductor shows excellent photoelectric response under the irradiation of visible light lamp at room temperature. Theoretical calculations and packing factor model both indicate that the loosely packed Bi2O2S is an excellent photoelectric material. When the Bi2O2S phase was annealed at 500 °C in an evacuated quartz tube, nanocrystals of Bi4O4S3 were obtained. The powder X-ray diffraction and electron microscope analyses (SEM, TEM, EDX) confirmed the thermal decomposition from orthorhombic Bi2O2S to tetragonal Bi4O4S3. The superconducting transition temperature of Bi4O4S3 was observed to be 4.6 K from the temperature-dependence measurements of electrical resistivity and magnetic susceptibility. Our results also provide a new method utilizing thermal decomposition to prepare a new phase without high temperature reaction.
We develop a facile one-step solid-state-chemistry strategy for synthesizing BiOI crystals with layered microstructure. The BiOI photocatalyst shows typical mesoporous feature with available surface ...area, considerable wide-spectrum light absorption and carriers lifetime properties, and remarkable solar to thermal effect for efficient solar-driven photocatalytic CO2 reduction to CH4. The engineered BiOI displays a superior CH4 formation performance with the space-time yield of 13.1 μmol g−1 h−1 and the selectivity of 82.3% as well as excellent photostability for CO2 photoreduction under solar light irradiation. Furthermore, the versatile BiOI can boost the photo-stimulated efficiency on clean H2 generation and pollutant degradation.
•Layered BiOI crystals were synthesized via one-step solid-state-chemistry strategy.•BiOI displays considerable wide-spectrum solar light absorption properties.•BiOI exhibits excellent performance for solar-driven CO2 reduction to useful CH4.•BiOI also shows high activities on H2 generation and pollutant degradation.
Noncentrosymmetric MoS2 semiconductors (1H, 3R) possess not only novel electronic structures of spin–orbit coupling (SOC) and valley polarization but also remarkable nonlinear optical effects. A more ...interesting noncentrosymmetric structure, the so-called 1T‴-MoS2 layers, was predicted to be built up from MoS6 octahedral motifs by theoreticians, but the bulk 1T‴ MoS2 or its single crystal structure has not been reported yet. Here, we have successfully harvested 1T‴ MoS2 single crystals by a topochemical method. The new layered structure is determined from single-crystal X-ray diffraction. The crystal crystallizes in space group P31m with a cell of a = b = 5.580(2) Å and c = 5.957(2) Å, which is a √3a × √3a superstructure of 1T MoS2 with corner-sharing Mo3 triangular trimers observed by the STEM. 1T‴ MoS2 is verified to be semiconducting and possesses a band gap of 0.65 eV, different from metallic nature of 1T or 1T′ MoS2. More surprisingly, the 1T‴ MoS2 does show strong optical second-harmonic generation signals. This work provides the first layered noncentrosymmetric semiconductor of edge-sharing MoS6 octahedra for the research of nonlinear optics.
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