Controllable Synthesis of Carbon-Coated SiOx Particles through a Simultaneous Reaction between the Hydrolysis-Condensation of Tetramethyl Orthosilicate and the Polymerization of 3-Aminophenol.

Core-shell particles are desirable for many applications, but the precise design and control of their structure remains a great challenge. In this work, we developed a strategy to fabricate carbon-coated SiOx (SiOx@C) core-shell particles via a sol-gel method using the simultaneous hydrolysis-condensation of tetramethyl orthosilicate (TMOS), the polymerization of 3-aminophenol and formaldehyde in the presence of ammonia as a basic catalyst, and cetyltrimethylammonium bromide (CTAB) as a cationic surfactant in the mixed solution of water and methanol followed by the carbonization process. Results from this study provide new insight into the design of core-shell particles by using TMOS as an effective silica precursor for the first time with a well-controlled reaction rate and spherical morphology. To obtain an in-depth understanding of the formation of core-shell structure, a possible mechanism is also proposed in this article. When tested as an anode material for lithium ion batteries (LIBs), the obtained SiOx@C particles delivered a reversible capacity of 509.2 mAh g-1 at a current density of 100 mA g-1. This electrochemical performance is significantly better than those of similar composites without the core-shell structure. The capacity retention after 100 cycles was approximately 80%. These results suggest great promise for the proposed SiOx@C particles with core-shell structure, which may have potential applications in the improvement of various energy-storage materials.

Microwave-Assisted Synthesis of C/SiO2 Composite with Controllable Silica Nanoparticle Size.

A C/SiO2 composite was produced from 3-aminophenol and tetraethyl orthosilicate (TEOS) by a synthesis protocol that involved microwave irradiation. This protocol featured simultaneous 3-aminophenol polymerization and TEOS hydrolysis and condensation, which were achieved rapidly in a microwave reactor. The SiO2 component was formed from low-concentration TEOS confined in cetyltrimethylammonium bromide micelles. We demonstrated a control of the SiO2 particle size, ranging from 20 to 90 nm, by varying the 3-aminophenol concentration. The carbon component provided a microporous structure that greatly contributed to the high specific surface area, 375 m2/g, and served as a host for the nitrogen functional groups with a content of 5.34%, 74% of which were pyridinic type. The composite formation mechanism was clarified from time-series scanning electron microscopy images and dynamic light scattering analysis. An understanding of the composite formation mechanism in this protocol will enable the design of composite morphologies for specific applications.