Lu Shang

Graphene‐Supported Ultrafine Metal Nanoparticles Encapsulated by Mesoporous Silica: Robust Catalysts for Oxidation and Reduction Reactions

Graphene nanosheet-supported ultrafine metal nanoparticles encapsulated by thin mesoporous SiO2 layers were prepared and used as robust catalysts with high catalytic activity and excellent high-temperature stability. The catalysts can be recycled and reused in many gas- and solution-phase reactions, and their high catalytic activity can be fully recovered by high-temperature regeneration, should they be deactivated by feedstock poisoning. In addition to the large surface area provided by the graphene support, the enhanced catalytic performance is also attributed to the mesoporous SiO2 layers, which not only stabilize the ultrafine metal nanoparticles, but also prevent the aggregation of the graphene nanosheets. The synthetic strategy can be extended to other metals, such as Pd and Ru, for preparing robust catalysts for various reactions.

Carbon quantum dots/TiO2 composites for efficient photocatalytic hydrogen evolution

Carbon quantum dots modified P25 TiO2 composites (CQDs/P25) with a “dyade”-like structure were prepared via a facile one-step hydrothermal reaction. CQDs/P25 exhibited improved photocatalytic H2 evolution under UV-Vis and visible light (λ > 450 nm) irradiation without loading any noble metal cocatalyst, compared to pure P25. A possible mechanism of the photocatalytic H2 production activity over CQDs/P25 was proposed based on detailed measurements of the transient photocurrent response, surface photovoltage and hydroxyl radicals. CQDs play dual roles on the improved photocatalytic activity of CQDs/P25. Under UV-Vis light irradiation CQDs act as an electron reservoir to improve the efficient separation of the photoinduced electron–hole pairs of P25. However, under visible light irradiation CQDs act as a photosensitizer to sensitize P25 into a visible light response “dyade” structure for H2 evolution.

Well‐Dispersed ZIF‐Derived Co,N‐Co‐doped Carbon Nanoframes through Mesoporous‐Silica‐Protected Calcination as Efficient Oxygen Reduction Electrocatalysts

A well-dispersed Co,N co-doped carbon nanoframework (Co,N-CNF) with hierarchically porous structure is successfully synthesized from zeolitic imidazolate framework (ZIF) precursors via a mesoporous-silica-protected calcination strategy. By preventing the irreversible fusion and aggregation during the high-temperature pyrolysis step with this protection strategy, the Co,N-CNF exhibits comparable oxygen reduction reaction (ORR) catalytic activity to that of commercial Pt catalysts with the same loading.

Nitrogen-Doped Porous Carbon Nanosheets Templated from g-C3N4 as Metal-Free Electrocatalysts for Efficient Oxygen Reduction Reaction

Nitrogen-doped porous carbon nanosheets (N-CNS) are synthesized by hydrothermal carbon coating of g-C3 N4 nanosheets followed by high-temperature treatment in N2 . g-C3 N4 serves as a template, nitrogen source, and porogen in the synthesis. This approach yields N-CNS with a high nitrogen content and comparable oxygen reduction reaction catalytic activities to commercial Pt/C catalysts in alkaline media.

Ultrafine NiO Nanosheets Stabilized by TiO2 from Monolayer NiTi-LDH Precursors: An Active Water Oxidation Electrocatalyst

Faceted NiO nanoparticles preferentially exposing high surface energy planes demand attention due to their excellent electrocatalytic properties. However, the activity of faceted NiO nanoparticles generally remains suboptimal due to their large lateral size and thickness, which severely limits the availability of coordinatively unsaturated active reactive edge and corner sites. Here, ultrafine NiO nanosheets with a platelet size of ∼4.0 nm and thickness (∼1.1 nm) stabilized by TiO2 were successfully prepared by calcination of a monolayer layered double hydroxide precursor. The ultrafine NiO nanosheets displayed outstanding performance in electrochemical water oxidation due to a high proportion of reactive NiO {110} facets, intrinsic Ni(3+) and Ti(3+) sites, and abundant interfaces, which act synergistically to promote H2O adsorption and facilitate charge-transfer.

Facile synthesis of hierarchical ZnIn2S4 submicrospheres composed of ultrathin mesoporous nanosheets as a highly efficient visible-light-driven photocatalyst for H2 production

Flower-like spherical ZnIn2S4 superstructures about 500 nm in diameter composed of ultrathin 2–3 nm thick mesoporous nanosheets were synthesized in several minutes by facile polyol-mediated hot-injection. Due to their higher specific surface area and constituent ultrathin mesoporous nanosheets, the hierarchical ZnIn2S4 superstructures exhibited highly efficient visible-light-driven photocatalytic H2 production activity compared with the typical flower-like ZnIn2S4 microspheres prepared by the conventional hydrothermal method. Furthermore, this polyol-mediated hot-injection synthesis strategy is also applicable for the facile synthesis of other metal sulphide nanomaterials with different morphologies, such as CdS quantum dots, Bi2S3 nanorods, and hierarchical flower-like In2S3 and SnS spheres.

Spontaneous Organization of Inorganic Nanoparticles into Nanovesicles Triggered by UV Light

A novel versatile light-triggered strategy is developed to organize inorganic nanoparticles (NPs) into nanovesicles with single or multiple layers in mixed solvents. This strategy constitutes a new assembly mechanism based on the photo-oxidation of thiol ligands. Compared with currently-used individual semiconductor NPs, the prepared CdSe QD vesicles exhibit an improved catalytic activity and unprecedented catalytic stability towards solar-driven hydrogen production. This light-triggered approach to functional nanoarchitectures would lead to new opportunities in various applications.

Highly luminescent nitrogen-doped carbon quantum dots as effective fluorescent probes for mercuric and iodide ions

Nitrogen-doped carbon quantum dots (N-CQDs) with strong blue fluorescence and a high quantum yield of 66.8% were synthesized via a facile one-pot hydrothermal treatment with ammonium citrate and ethylenediamine as carbon and nitrogen sources, respectively. The blue fluorescence emission is independent of the excitation wavelengths and is very stable in a wide pH range. These N-CQDs, dispersed well in water and other polar solvents, showed a highly selective and sensitive detection of hazardous and toxic Hg2+ in the range of 10 nM to 20 μM through a fluorescence quenching process. The N-CQDs quenched by Hg2+ exhibited high selectivity and sensitivity for I− in the range of 0.5 μM to 40 μM via a fluorescence recovery process. A possible charge transfer process responsible for the effective detection was proposed according to the UV-vis absorption and fluorescence decay measurements.

Recent Advances in the Synthesis, Characterization and Application of Zn+‐containing Heterogeneous Catalysts

Monovalent Zn+ (3d104s1) systems possess a special electronic structure that can be exploited in heterogeneous catalysis and photocatalysis, though it remains challenge to synthesize Zn+‐containing materials. By careful design, Zn+‐related species can be synthesized in zeolite and layered double hydroxide systems, which in turn exhibit excellent catalytic potential in methane, CO and CO2 activation. Furthermore, by utilizing advanced characterization tools, including electron spin resonance, X‐ray absorption fine structure and density functional theory calculations, the formation mechanism of the Zn+ species and their structure‐performance relationships can be understood. Such advanced characterization tools guide the rational design of high‐performance Zn+‐containing catalysts for efficient energy conversion.

Shape-controlled synthesis of polyhedral 50-facet Cu2O microcrystals with high-index facets

Perfect polyhedral 50-facet Cu2O microcrystals enclosed by high ratio exposed high-index {211}, {522} or {311} facets were successfully synthesized by a facile wet-chemical route under mild temperature and normal pressure. The morphological evolution of 50-facet Cu2O polyhedra was studied carefully and in detail by adjusting reaction parameters such as reaction temperature, reaction time, the concentration and type of alkali metal hydroxides and copper salts, and the amount of the reduction agent glucose. On the basis of these results, a formation mechanism of these polyhedra was tentatively proposed. As compared with Cu2O cubes and octahedra with low-index {100} and {111} facets, respectively, the as-prepared 50-facet Cu2O polyhedra showed higher photocatalytic activities towards the decomposition of the organic dye methyl orange due to more catalytic active sites being held in the high-index facets.