Pei Yuan

Sustainable seaweed-based one-dimensional (1D) nanofibers as high-performance electrocatalysts for fuel cells

A high-performance one-dimensional (1D) nanofibrillar N–Co–C oxygen reduction reaction (ORR) catalyst was fabricated via electrospinning using renewable natural alginate and multiwalled carbon nanotubes (MWCNTs) as precursors, where Co nanoparticles (NPs) are encapsulated by nitrogen (N)-doped amorphous carbon and assembled on MWCNTs. The 1D morphology not only prevents the aggregation of the Co NPs, but also provides a typical multimodal mesoporous structure which is beneficial for the O2 diffusion and the migration of adsorbed superoxide. In combination with the high conductivity of CNTs, the N-doped amorphous carbon shell can exert electron release on the encapsulated Co NPs, and thus enhance the ORR activity. It is also a protective layer that stabilizes the Co NPs, which ensures a high ORR activity of the catalysts in both alkaline and acid media and long-term durability. So compared with a commercial Pt/C catalyst, as expected, the N–Co–C nanofiber reported herein exhibited a comparable current density and onset potential (−0.06 V), with better durability in alkaline and acid solutions and better resistance to crossover effects in the ORR.

A simple approach to prepare monodisperse mesoporous silica nanospheres with adjustable sizes

A new and facile approach has been developed to prepare monodisperse mesoporous silica nanospheres (MMSNs) with controlled particle sizes and pore structures. In our approach, MMSNs were synthesized simply in a sodium acetate solution without adding any other alkali or alcohol additives. MMSNs have a spherical shape and uniform particle sizes, which can be adjusted from 50 to 110 nm by increasing the reaction temperature from 40 to 80 °C. By performing a subsequent hydrothermal treatment (HT) under basic condition (pH=~11.5) at 130 °C, the mesoporous pore volume and surface area can be enhanced, while keeping the mono-dispersion characteristics and the mesopore size almost unchanged. The pore sizes of MMSNs can be adjusted from 2.8 to 4.0 nm under acidic solutions by changing the HT temperature from 100 to 130 °C. The formation process of MMSNs has been investigated by transmission electron microscopy (TEM) and attenuated total reflection Fourier transform infrared (ATR-FTIR) techniques. A spherical micelle templating mechanism is proposed to explain the formation of MMSNs in our system, which is different from that of traditional highly ordered mesoporous silica nanoparticles (MCM-41).

Preparation of supported hydrodesulfurization catalysts with enhanced performance using Mo-based inorganic–organic hybrid nanocrystals as a superior precursor

This article presents a novel strategy to prepare alumina-supported Mo and MoNi hydrodesulfurization (HDS) catalysts using Mo-based inorganic–organic hybrid nanocrystals (HNCs) as a superior precursor under moderate hydrothermal conditions. The characterization results revealed that each HNC in the aqueous solution has a size of ca. 2.5 nm and shows a core–shell structure with one Mo8O264− as the inorganic core and long-chain quaternary ammonium cations as the organic shell. The proposed approach not only significantly promotes the dispersion of supported Mo species, but also greatly enhances the stacking of MoS2 active phase, endowing the resulting catalysts with sufficient and accessible Ni–Mo–S active sites and thereby with a remarkably enhanced HDS performance as compared to their counterparts prepared by the conventional impregnation method. Thereby, a novel precursor for preparing Mo-based catalysts was successfully developed and the roles of the HNC-derived preparation method in tuning the size and morphology of supported metal sulfide nanoparticles in HDS catalysts were demonstrated, shedding a light on the rational design and controllable fabrication of supported metal sulfide catalysts.

Synthesis of zeolite Y from natural aluminosilicate minerals for fluid catalytic cracking application

An energy-saving and environmentally friendly approach to synthesize zeolite Y from natural aluminosilicate minerals without the involvement of aluminum- and silicon-containing inorganic chemicals was developed. When used as a fluid catalytic cracking catalyst, the resulting zeolite Y exhibited an outstanding catalytic cracking performance.

Enrichment and detection of peptides from biological systems using designed periodic mesoporous organosilica microspheres

Periodic mesoporous organosilica microspheres (PMOMs) are designed with integrated structural features, including a cubic mesostructure, hydrophobic wall composition, a uniform pore size of ≈3 nm, and a spherical morphology in micrometers, all advantageous for size-selective and highly efficient enrichment of peptides from mixtures. Consequently, PMOMs can be used to capture peptides in a range of complex biological systems.

Solving Complex Concentric Circular Mesostructures by Using Electron Tomography

Inside knowledge: The true internal structure of a complex concentric circular hexagonal mesostructure has been solved for the first time by using electron tomography. This technique allows the mesostructure containing closed rings to be differentiated from a closed helical mesostructure. The key step is the use of tomographic slices with a thickness of less than 1 nm so that the interior structure can be observed (see picture).

Catalytic Properties of a Hierarchical Zeolite Synthesized from a Natural Aluminosilicate Mineral without the Use of a Secondary Mesoscale Template

A hierarchical ZSM‐5 zeolite with a bimodal meso‐microporous system, high crystallinity, and a large surface area and meso‐micropore volume was successfully synthesized from a natural layered aluminosilicate mineral rectorite without using a secondary mesoscale template. The physicochemical and catalytic properties of the hierarchical ZSM‐5 zeolite were extensively characterized. The results showed that the mesopores of the synthesized hierarchical ZSM‐5, which are almost slitlike intercrystal pores, originate from the construction of primary nanorods of the ZSM‐5 zeolite. Analysis of the crystallization process revealed that the undissolved rectorite debris acted as seed crystals and played a structure‐directing role, which is the key factor that influences the formation of the hierarchical structure. Such a hierarchical ZSM‐5 zeolite, as a result of its unique structural characteristics and increased accessibility of acid sites, possessed a remarkably enhanced activity for the cracking of 1,3,5‐triisopropylbenzene, a dramatically higher anti‐deactivation ability for cumene conversion, and a significantly improved propylene‐boosting performance for heavy oil cracking than the other catalysts tested.

Electron-Tomography Determination of the Packing Structure of Macroporous Ordered Siliceous Foams Assembled From Vesicles

The packing structures of macroporous ordered siliceous foams (MOSFs) are systematically investigated by using a 3D electron tomography technique and the nanostructural characteristics for layered MOSFs are resolved. MOSF materials adopt an ordered 2D hexagonal arrangement in single-layered areas, regular honeycomb patterns in double-layered samples, and polyhedric cells similar to a Weaire-Phelan structure in multilayered areas, all following the principle of minimizing surface area, which is well understood in soap foams at the macroscopic scale. In surfactant-templated materials, liquid-crystal templating is generally applied, but here it is revealed that the surface-area-minimization principle can also be applied, which facilitates the design and synthesis of novel macroporous materials using surfactant molecules as templates.

Periodic Mesoporous Organosilicas with Helical and Concentric Circular Pore Architectures

This study systematically investigates periodic mesoporous organosilicas (PMOs) with controlled helical and concentric circular (CC) pore architectures prepared through a basic-catalyzed sol-gel process by using an achiral cationic surfactant trimethyloctadecylammonium bromide (C(18)TAB) as a structure-directing agent, perfluorooctanoic acid (PFOA) as an additive, and 1,2-bis(triethoxysilyl)ethane (BTEE) as a hybrid silica precursor. By increasing the weight ratio of PFOA/C(18)TAB, a pore architecture transition of PMO materials from hexagonal-arrayed, straight longitudinal channels to helical and CC mesostructures is achieved; such a transition has not been observed before in PMO materials. Our discovery is helpful in understanding the supramolecular cooperative assembly of hybrid materials and their structural and morphological evolution, which are important in the future applications of PMO materials.

Synthesis, self-assembly and disassembly of mono-dispersed Mo-based inorganic–organic hybrid nanocrystals

Mono-dispersed Mo-based inorganic–organic hybrid nanocrystals (HNCs) in water phase with a uniform size of ca. 3 nm have been successfully synthesized via a simple and facile method at room temperature. With the help of comprehensive characterizations, the chemical composition and structure of this hybrid material was determined: Mo8O264− as the inorganic core and long-chain quaternary ammonium cations as the organic shell. Interestingly, the resultant nanocrystals can spontaneously self-assemble into lamellar mesoscale nanocomposites with an alternative arrangement of inorganic and organic layers when simply removing water or adding ethanol into the solution. The distance between two layers depends on the length of the quaternary ammonium cations used, indicating that the cationic surfactant functions as a structure-directing agent and induces the formation of an ordered lamellar mesostructure. Moreover, we found that the lamellar mesoscale structure can be disassembled into well-dispersed HNCs when being re-dispersed into a large amount of water. The unique self-assembly and disassembly behavior of the mono-dispersed HNCs may have great potential for fabricating Mo-based functional materials.