Topological Transformation of Thioether-Bridged Organosilicas into Nanostructured Functional Materials

The strong interest in nanostructured functional materials has motivated the scalable production of high quality mesoporous silicas and carbonaceous materials. Although many approaches have been explored for this goal, it is highly desired and still remains a challenge to develop a straightforward strategy for simple and cost-effective fabrication of nanostructured functional materials. Here we demonstrate a simple sol–gel preparation of bis­[3-(triethoxysilyl)­propyl]­tetrasulfide-based organosilica nanostructured materials and their topological transformations, through which porous spherical silica or carbon and hollow silica or carbon capsule are synthesized. As a representative application, the hollow carbon capsule is employed as a catalyst support for dispersion of high loading of Pt, which exhibits much higher catalytic activity toward oxygen reduction reaction than other porous carbon materials prepared in this work due to its larger surface area and mesoporous volume, particularly the unique architecture composed of a hollow macroporous core and a mesoporous shell, facilitating not only small size and good dispersion of Pt nanoparticles but also fast mass transport

N‑Doped Hierarchical Hollow Mesoporous Carbon as Metal-Free Cathode for Dye-Sensitized Solar Cells

In this study, novel nitrogen (N)-doped hollow core-mesoporous shell carbon (N-HCMSC) capsules with high surface area are synthesized by simple three-step processes and explored as metal-free counter electrode (CE) in comparison with undoped HCMSC in dye-sensitized solar cells (DSSCs). It is shown that N-HCMSC significantly improves the catalytic activity toward the reduction of both Co­(bpy)₃³⁺ and I₃^– due to much lower charge-transfer resistance (<i>R</i>_CT) at the CE/electrolyte interface. This is attributed not only to excellent surface properties including three-dimensionally interconnected hierarchical marco/mesoporosity with high surface area but also to N doping in N-HCMSC framework. Among various N species in the N-HCMSC framework, pyridinic and quaternary N species are considered to contribute significantly to the catalytic activity. In addition, N-HCMSC CE exhibits much better electrochemical stability than Pt CE toward both Co­(bpy)₃^2+/3+ and I^–/I₃^– redox reactions. The N-HCMSC enhances the cell efficiency and fill factor up to 8.76 and 77.6%, respectively, at one sun illumination and is readily applicable as a potential alternative of costly Pt-based CE for DSSCs with Y123-sensitized photoanodes