A team from Hong Kong Polytechnic University (PolyU) developed a new nanostructure embedded in a semiconductor nanofiber which results in excellent conductivity. The nanocomposite addresses a conductivity conductivity inhibitor, with potential to improve a wide range of applications, from batteries and solar cells to air purifiers.
While semiconductors are used to a large extent, their efficiency has been limited by the natural process of photogenerated electrons in recombination with "holes" or potential electron support points. This reduces the moving current of electrons generated by light or external current and as a consequence reduces the efficiency of the device. PolyU's Department of Mechanical Engineering designed a composite nanofibre that essentially provides a dedicated electrical transmission control when generated, eliminating the problem of recombination of electron holes.
The innovation was awarded the gold medal with the jury's congratulations on the 45th International Exhibition of Inventions in Geneva in 2017.
The team avoided recombination by introducing a strong conductive nanostructure made of carbon nanotubes and the graph in a titanium dioxide (TiO2) composite nanofibre. The electrons and charges can be transported efficiently in the graph nucleus as soon as they are formed before being combined with the "holes" of the nanofibes. Led by Wallace Leung, the team has tested the efficiency of nanocomposite in solar cells and air purification photocatalysts.
The embedded nanocomposites in TiO2 component of color sensitive and perovskite-based solar cells, which are examined as an alternative to conventional silicon-based photovoltaic cells. The nanocomposite increased the energy conversion rates of the solar cells 40 percent to 66 percent.
Ten2 nanoparticles are the most common photocatalyst material in commercially available air purifying or disinfecting devices. But TiO2 can only be activated with ultraviolet light, which makes it much less efficient indoors. It is also ineffective when converting nitric oxide (NO) to nitrogen dioxide (NO2), at a rate of less than 10 percent.
When PolyU's nanostructure was embedded in a photocatalyst, it provided a graph superhighway for electrons to transport faster to generate superanions to oxidize absorbed contaminants, bacteria and viruses. The graft core also significantly increased the surface exposed to light absorption and capture of harmful molecules. It also harvested more light energy over all wavelengths. Semiconductor nanofibres converted about 70 percent of NO to NO2, seven times more than usual TiO2 nanoparticles.
They also tested how well their nanostructure breaks down formaldehyde, a nasty volatile organic compound commonly found in new or renovated buildings and new cars. PolyU's embedded graphite catalyst could again degrade three times more formaldehyde than TiO2 nanoparticles without added nanostructure.
The new nanocomposite has a wide range of other potential applications, such as hydrogen production through water scattering, biochemical sensors with increased speed and sensitivity, and lower impedance lithium batteries and increased storage.
Team develops new semiconductor nanofiber with excellent chargeability