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.