Photocatalytic performance evaluation of flame-sprayed and polymeric suspension coatings from TiO2 nanoparticles

BACKGROUND Heterogeneous photocatalysis offers an interesting alternative to mitigate air pollution by using materials capable of reacting with toxic gases under ultraviolet light. One of these materials is titanium dioxide (TiO2), and thus it is necessary to analyze and improve its photocatalytic response for air depollution, in order to facilitate its use in surface applications.RESULTS The photocatalytic ability of the synthesized TiO2 particles to remove nitric oxide (NO) was tested, and it was found that both the anatase and rutile phases present in the samples led to a NO abatement capacity of asymptotic to 60% eta NO. Two different methods to coat surfaces with TiO2 particles were evaluated: thermal spray by oxyacetylene flame and dripping of polymeric suspensions of TiO2. A more detrimental effect on photocatalytic efficiencies was found using polymeric suspension rather than flame-spraying as coating method. This was despite the anatase transformation to rutile and Ti7O13 that TiO2 particles undergo using the latter process as a consequence of heat transfer from the flame to the particles during the coating formation.CONCLUSION Results obtained in this research demonstrate that polymeric suspensions inhibit the photocatalytic activity of TiO2 nanoparticles, probably due to the formation of a polymeric matrix on samples that constrains the action of pollutant and testing factors on samples. However, the thermal method can help retain part of the photocatalytic capability to abate NOx, despite depletion in the anatase content resulting from the heat transfer to the TiO2 raw particles sprayed to form coatings.