National Tsing Hua University Researchers Reveal Pyrolysis Process to Produce Carbon-Coated Metal Oxide Nano-Particles

FIG. 4, U.S. Patent Application 20100035750.is a transmission electron microscope (TEM) picture of  carbon-coated TiO2 nano-particles obtained with pyrolysis at 800.degree. C by Taiwanese Researchers
National Tsing Hua University (Hsinchu City, TW) researchers have developed a  method of preparing carbon-coated metal oxide nano-particles and carbon-coated metal oxide nano-particles. The method of preparation is described in U.S. Patent Application 20100035750.
The method includes the following steps: a precursor of a polymer is polymerized on metal oxide nano-particles to form polymer-coated metal oxide nano-particles. Then, pyrolysis is conducted to carbonize the polymer coated on the metal oxide nano-particles, so as to form carbon-coated metal oxide nano-particles, according to inventors Chia-Min Yang, Yu-Chuan Hsu, Huang-Ching Lin, Yi-Ting Liao and  Chien-Wei Lue
Among all the functional materials to be synthesized on the nano-scale, metal oxides are particularly attractive candidates, from a scientific point and a technological point of view. The unique characteristics of metal oxides make them the most diverse class of materials, with properties covering almost all aspects of material science. The great variety of structures makes them the primary target in solid-state chemistry and provides the basis for designing new materials. In addition, metal oxide materials exhibit fascinating electronic and magnetic properties, including metallic or insulating and ferro-, ferri- or antiferromagnetic behavior.
All these properties make metal oxides a vital constituent in technological applications like gas sensing, electroceramics, catalysis, energy conversion, data storage and so on. Among them, oxides of titanium, tin, iron and other metals that possess moderate band gaps can absorb visible to ultra-violet light to proceed photochemical reactions, such that these materials can serve as photocatalysts.

Some of these metal oxide photocatalysts are commonly used in daily life, and their potential in photochemical elimination/decomposition of organic pollutants for environmental purpose and in photovoltaics and solar energy utilization are widely recognized and are intensively studied worldwide.

A conventional method of preparing a metal oxide nano-structure is the aqueous sol-gel technique using a suitable precursor, but this technique has difficulties in reducing the particle size and controlling the reaction condition. Therefore, in recent years, the non-aqueous sol-gel technique is also adopted.

On the other hand, coating a layer of carbon on the surface of a nano-metal oxide photocatalyst can effectively improve the crystallinity stability, optical activity and the performance in adsorbing dye molecules or contaminants. In the conventional method of preparing carbon-coated metal oxide nano-particles, already formed metal oxide nano-particles and a polymer are mixed, and then high-temperature pyrolysis is conducted to carbonize the polymer on the nano-particles. However, the thickness of the carbon coating formed with the above method is usually not uniform, and the carbon content of the nano-particles is difficult to control.

National Tsing Hua University researchers developed a method of preparing carbon-coated metal oxide nano-particles, so as to solve the problems in the prior art. The preparation method includes the following steps: a precursor of a polymer is polymerized on metal oxide nano-particles to form polymer-coated metal oxide nano-particles, wherein the metal oxide contains one or more metals. Pyrolysis is then conducted to carbonize the polymer coated on the metal oxide nano-particles. 


In some embodiments, forming the polymer-coated metal oxide nano-particles includes the following steps: a precursor of the metal oxide and the precursor of the polymer are uniformly dispersed in a solvent to form a solution. Then, the solution is heated to cause reaction, such that the precursor of the polymer is polymerized on the just formed metal oxide nano-particles to form the polymer. The preparation method further includes separating the polymer-coated metal oxide nano-particles from the solution after the polymer-coated metal oxide nano-particles are formed.