Jian Zhi

Palladium nanoparticles in carbon thin film-lined SBA-15 nanoreactors: efficient heterogeneous catalysts for Suzuki–Miyaura cross coupling reaction in aqueous media

Embedding Pd nanoparticles in carbon thin film-lined SBA-15 nanoreactors provides highly efficient catalysts for heterogeneous cross coupling reactions in aqueous media. No leaching or aggregation of Pd nanoparticles was found in these nanoreactors after reusing them several times. The carbon thin film lining of these nanoreactors was further confirmed with small molecular arene probing experiments.

Embedding Co3O4 nanoparticles in SBA-15 supported carbon nanomembrane for advanced supercapacitor materials

A three dimensional porous carbon nanomembrane (CNM), silica-supported CNM (SS-CNM), is developed by formation of a self-assembled monolayer of an enediyne compound on the surface of mesoporous silica (SBA-15) followed by Bergman cyclization and carbonization. The SS-CNM is applied as a conductive support for the electroactive material Co3O4 to fabricate advanced supercapacitors. A large fraction of Co3O4 clusters (66% of total weight) are impregnated in the SS-CNM host to form regularly packed nanorods with diameters of 7 nm. The specific capacitance of the supercapacitor electrode material reaches 1086 F g−1 (1645 F g−1 based on Co3O4) with aqueous electrolyte. This extraordinary high performance of the electrode material is attributed to the unique pore structure of the SS-CNM support that enhances the use of active material and shortens the transport path of ions and electrons.

Synthesis of Ultrathin Mesoporous Carbon through Bergman Cyclization of Enediyne Self-Assembled Monolayers in SBA-15

In this work, a bottom-up synthesis of ultrathin mesoporous carbon was developed through Bergman cyclization of enediyne containing compounds immobilized inside of SBA-15 nanochannels and followed by pyrolysis. Raman spectroscopy confirmed the occurrence of thermal Bergman cyclization inside the channels. Further heating under elevated temperature produced nanotube arrays in good yield. TEM images revealed the formation of interconnected tubular carbon due to the microtunnels of template. Raman spectra showed moderate degree of graphitization. Formation of enediyne SAMs on a template followed by the processing sequence developed in this work is promising to construct carbon materials with various nanoscopic morphology, such as carbon nanotube, graphene, and giant fullerene.

Hierarchical MnO2 Spheres Decorated by Carbon-Coated Cobalt Nanobeads: Low-Cost and High-Performance Electrode Materials for Supercapacitors

MnO2 is a promising electrode material for supercapacitors, because it exhibits high theoretical specific capacitance (1380 F g(-1)) for electrical charge while also being inexpensive and environmentally benign. However, owing to its low electrical conductivity, the intrinsic pseudocapacity of MnO2 is not fully utilized. In this work, hierarchically structured spheres composed of MnO2 nanoplatelets and carbon coated cobalt nanobeads (MnO2-NPs@Co/C) are chosen as electrode materials for supercapacitor. With a Co/C mass loading of 19 wt %, the electrical conductivity of the hybrid is 122-fold larger than that of pristine MnO2, showing a specific capacitance of the constituent MnO2 as high as 1240 F g(-1), being close to the theoretical value. Such improved specific capacitance of MnO2-NPs@Co/C electrode is largely contributed from the enhanced double-layer charging and Faradaic pseudocapacity of MnO2. Moreover, the fabricated symmetrical supercapacitor also exhibits excellent cycling stability with 89.1% capacitance retention over 10000 cycles, as well as high energy densities in both aqueous and organic electrolyte (24 Wh kg(-1) and 33 W kg(-1), respectively). Compared with frequently used noble metals to enhance the electrochemical performance of MnO2, the utilization of low cost Co/C nanobeads is proven to be more efficient and thus showing great potential for commercial application.

Size-Controlled Synthesis of Conjugated Polymer Nanoparticles in Confined Nanoreactors†

Soluble conjugated polymeric nanoparticles are synthesized by Suzuki-type polycondensation of two monomers (Ax + By, x>2, y≥2) in the channel of ordered mesoporous silica-supported carbon nanomembranes (nanoreactors). These synthesized soluble conjugated microporous polymers (SCMPs) exhibit uniform particle-size distributions and well-controlled particle sizes. The control of particle size stems from the fact that the polycondensations exclusively take place inside the mesochannels of the nanoreactors. Photoluminescence studies show that polymeric nanoparticles with tetraphenylethene and pyrene substructures are highly fluorescent. The combination of both physical stability and processability offered by the soluble polymeric nanoparticles makes them particularly attractive in light emitting and other optoelectronic applications.

Study on the relation between pore size and supercapacitance in mesoporous carbon electrodes with silica-supported carbon nanomembranes

Electrochemical capacitors (ECs) have traditionally been considered as standing at the opposite end against batteries in energy–power diagram. They charge and discharge faster than batteries but are limited by much lower energy density. By optimizing the pore structure of porous electrode materials, the performance of ECs could overcome this limitation. However to date, no study has addressed the complex relationship between the texture parameters of the electrode materials and the supercapacitance of ECs. Using silica-supported carbon nanomembranes, four electrode materials with similar pore geometry are generated. The electrodes with a pore size of 4.14 nm shows the highest capacitance of 305 F g−1 in aqueous electrolytes. A new model is developed to simulate the accommodation of the solvated ions at the electrode surface. The simulation reveals that the optimal capacitance of ECs can be achieved using porous carbon electrode materials with open pores of 3.0–5.0 nm.

Surface confined titania redox couple for ultrafast energy storage

Practical large-scale energy storage should deliver high capacitance/capacity with an ultrahigh rate and do so economically over multiple cycles. Existing electrode materials, however, have fallen short of these requirements in one measure or another. Here, we have discovered a surface confined titania redox couple on black TiO2 nanotube arrays (B-TNAs). Such rapid Ti3+/Ti4+ conversion provides an outstanding rate for B-TNAs of 400 mA cm−2 in supercapacitors (SCs) and 200 C in lithium ion batteries (LiBs), with negligible capacitance/capacity fading for up to 15 000 cycles. The ultrafast pseudocapacitive behaviour from black titania suggests a new family of electrode materials, which may offer a way to overcome the present difficulties of SCs and LiBs in grid-scale energy storage systems.