Materials that are currently used as photocatalysts are mainly based on titanium dioxide. The problem with these materials is in, although high, but still limited photocatalytic activity. Therefore, new materials with even higher photocatalytic activity and new methods of their manufacturing are needed.
Several studies performed by different research groups concluded that zirconia shows a high photocatalytic affinity for degradation of hazardous hydrocarbons, chlorides and nitrides, such as methane, ethane, formic acid, methanol, formaldehyde, tetrachloromethane and nitrogen oxides. The thin zirconia layers are previously known from the state of the art, but are all very expensive and complicated to manufacture, which makes them practically non-applicable at the industrial level. Known procedures of synthesis encompass sol-gel processes, pyrolysis and calcination of zirconia as well as spin-coating processes. One of the main problems for practical application of zirconia thin layers is their stabilization. Stability is necessary for application of zirconia on surfaces of different products and components, for example industrial pipelines, parts of vehicles, rooftops and windows. Such applications facilitate a degradation of hazardous molecules present in atmosphere or produced as waste product during industrial processes.
Slovenian research institute has developed a two-phase process for industrial formation of thin zirconium dioxide (zirconia) layers. In the first phase, the chemical vapour deposition is used to form a thin layer of glassy alloy containing a large amount of zirconium, usually over 5 volumetric percent. For better stability and increased photocatalytic activity some copper, titanium and/or niobium ions are added. In the second phase, oxidation of thin layer in the presence of oxygen, elevated temperature and strong oscillating magnetic field is carried out. The oxidation is mediated by oxygen or any other oxygen containing gas. The second phase is very short, usually taking around half a minute. Following the described procedure a thin layer of tetragonal zirconia is produced. The procedure, e.g. both phases, can be carried out in a single chamber. Alternatively a high vacuum chamber can be used for deposition of a thin layer, while other steps are carried out in a separate chamber. The resulting thin layers of zirconia are 10 to 100 micrometers thick.
The advantage of described method is in its industrial applicability, a demand that has not been met so far. The method of synthesis is simple, fast and cost efficient. Prepared materials display improved catalytic activity when compared to common titania photocatalysts. The characteristics of thin layers of zirconia are independent of the crystallinity of the support material. The material can be applied in different pipelines, especially for chemical industry, industrial filters, for parts and/or catalysts in automotive industry, rooftops, walls, facades and similar. Thin layers of zirconia are also applicable in photovoltaics and electronics. The surface of such layers can be easily cleaned after the contamination, with no detectable loss of photocatalytic activity. Such losses are otherwise common for the powder type zirconia.
For the characterization of photocatalytic activity a model organic pollutant compounds, such as benzoic acid and di-tert butyl catechol (DTBC) have been used. The comparison showed up to four-time increase in photocatalytic degradation of model pollutants when compared to commonly used titania photocatalyst under the same operating conditions.
Industrial partners are sought, preferably from chemical industry, producers of industrial filters, for parts and/or catalysts in automotive industry, manufacturers of rooftops, walls, facades and similar products, producers of photovoltaics and electronics. Industrial partners are expected to apply the technology at industrial level. License agreement is sought.