Black titanias for photocatalysis, solar cells and environmental applications

Description of the technology

The Molecular Nanotechnology Lab (NANOMOL) of the University of Alicante (Spain) and the Organometallic Molecular Materials Research Group from the University of La Rioja (Spain) have developed a simple, versatile and cheap approach for the synthesis of black titanias with excellent photocatalytic activity and good thermal and hydrothermal stability. The technology has been successfully tested and can be applied in degradation of organic pollutants, DeNOx processes or as an alternative in solar cells. The technology is protected by a Spanish patent application and the group is looking materials producing companies interested in acquiring the technology for commercial purposes, or to establish partnerships for the development and industrial scale, or companies interested on testing the materials for photocatalysis, solar cells or environmental applications.

Specifications

Titanium dioxide, also known as titania, is one of the most widely used semiconductors photocatalysts in water/air purification, hydrogen production from water splitting, pollutants elimination (VOx and NOx) and high-efficiency dye-sensitized solar cells (DSC). Titania has many advantages: it is cheap, abundant, non-toxic, chemically stable, and biocompatible, and is widely used in health care products as well as in paints. However, TiO2 overall efficiency for solar-driven photocatalysis is very limited, because of its large band gap (3.2 eV for anatase phase) which corresponds to the UV light range (380 nm anatase phase) which accounts for less than 5% of the total solar irradiation. Therefore, significant efforts are being conducted to reduce its band gap to the 400-900 nm spectral range (visible and near-IR), but the results are so far from the market requirements. So, there is an urgent need for a new and disruptive technology based on a simple and cheap synthesis methodology which will allow for the engineering of the band gap of semiconductors to fully utilize the visible light range, giving these promising photoactive materials a commercial opportunity. Two Spanish research groups from University, with broad experience in the field of nanotechnology, have developed a new synthesis approach to reduce the band gap of titania materials by using an environmentally friendly one-pot method (no surfactant, using only water and a minimum quantity of ethanol as solvents and mild conditions) that allows the incorporation of different functionalities (organic compounds, dyes, metal complexes…) in the structure of titania. Hybrid materials have anatase structure and BET areas of c.a. 300 m2/g, By using this approach, the researchers have produced a highly active and stable photoactive black titania, with a remarkable reduction of its band gap (from 3.20 eV to 2.74 eV), being able to absorb in the whole visible range (Fig. 1). The black titania exhibited enhanced photocatalytic activity under UV and visible light in the Rhodamine 6G degradation reaction under both UV and visible irradiation (TOC measurements confirmed degradation towards CO2), Fig. 2, left. Recycling tests under the same conditions prove the stability of this hybrid titania (Fig. 2, right). This new photocatalyst has been recently tested indicating very good NOx degradation values with high selectivity towards nitrates when tested in a road. This material constitutes the only example on the use of polymetallic titanium alkoxides as organotitania precursors for the synthesis of stable and visible-light active titanias. The technological potential of these hybrid titanias covers areas ranging from photocatalytic splitting of water for hydrogen production or purification of water/air to dye-sensitized solar cells or materials for example, for self-cleaning applications.

Main advantages of its use

• Band gap control is carried out by crystal engineering instead of the traditional band gap engineering based on chemical methods (i.e. doping and hydrogenation) diminishing the charge-recombination probability.
• Crystal disruptors are incorporated into the bulk of the semiconductor which greatly protects them (avoiding the problems associated to the stability of the dye) and improves the electronic transference of the charge-transfer dye.
• This black titania is able to use the whole UV and visible range of solar radiation showing a really high photocatalytic activity and thermal stability with an increase of only 0.6% in the production cost in comparison with control titania.
• The proposed synthetic method is very simple, versatile and can be carried out at low temperature and pressure, avoiding the use of hazard conditions, such as hydrogen or ammonia at high temperatures, with the consequent saving.

Applications

• Materials degradation of contaminants in soil, water or asphalt.
• Photocatalysis. Companies producing photocatalytic materials.
• Solar panels. Companies producing materials for solar panels for the enhancement of its efficiency.

Additional information (attached documents)

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