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 new synthetic approach for the synthesis of black titanias with outstanding photocatalytic activity under visible light. This novel procedure is simple (one-pot synthesis), versatile and cheap (mild conditions, without the concurrence of surfactants, calcinations or high temperature steps) thereby saving cost in materials and energy.
The technology has been developed and successfully tested at the laboratory getting black titanias with excellent photocatalytic activity both in the ultraviolet, and what is more interesting, in the whole visible range, and good thermal and hydrothermal stability. These materials find application in very different areas such as the degradation of organic pollutants, DeNOx proces
We 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, we 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.
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.
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ADVANTAGES OF THE DEVELOPED TECHNOLOGY
• 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.
• Our black titania is able 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.
• 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.
• 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.
INNOVATIVE ASPECTS OF THE TECHNOLOGY
• The titania is black, and then absorb in the whole visible range (band gap 2.74 eV) and maintains its photocatalytic activity at least after 5 cycles reaction with an efficiency of 95 %.
• The synthesis process is simple, inexpensive and versatile (a wide variety of functional compounds can be incorporated in the structure of the titania lattice avoiding blocking the mesoporosity and maintaining the anatase structure).
• Excellent thermal and hydrothermal stability. The functionality is incorporated into the structure of the titania being protected thereby.
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• Photocatalysis. Companies producing photocatalytic materials.
• Solar panels. Companies producing materials for solar panels for the enhancement of its efficiency.
• Materials degradation of contaminants in soil, water or asphalt.
Rodriguez Roselló, Iván
