Efficient day-and-night NO2 abatement by polyaniline/TiO2 composites

The abatement of NOx emission represents a global concern in the field of environmental pollution. In this respect, costly approaches, using high reaction temperatures are required. However, innovative strategies have been proposed based on photocatalytic NOx abatement [1, 2]. Thanks to its chemical stability, wide availability, low cost, and reliable structure/electronic properties TiO2 is one of the most investigated photocatalyst for NOx photocatalytic oxidation [3, 4]. However, even though TiO2 is highly active under UV light irradiation, its activity under sunlight is very low [2]. To address this disadvantage, the surface of this material can be properly modified by doping strategies or by coupling with other semiconductors, such as titanate perovskite [2]. Nevertheless, although these materials offer interesting alternatives under light irradiation, by the night photocatalysis is completely inactive. In order to overcome this limitation, new day and night active materials have to be developed. In this regard, polyaniline (PANI), one of the main exponent of the class of conducting polymers, could represent an important alternative, allowing to exploit its redox properties, related on the presence of imino-quinoid/amino-benzenoid groups. In the present study, PANI/TiO2 composites were fabricated by an innovative green UV-assisted procedure, characterized by a combination of structural, morphological, and spectroscopic techniques, and applied to the NOx abatement under both UV/LED light irradiation and in dark conditions. The amount of PANI in the final composite was accurately dosed in order to enhance the night-time activity without affecting photocatalytic properties. The role of PANI in the NO2 abatement was also investigated on the basis of their physicochemical characteristics. The best materials were subjected to recycle tests in order to demonstrate their stability under the reaction conditions. [1] J. Ângelo, L. Andrade, L. M. Madeira, A. Mendes, J. Environ. Manage. 2013, 129, 522. [2] V.-H. Nguyen, B.-S. Nguyen, C.-W. Huang, T.-T. Le, C. C. Nguyen, T. T. N. Le, D. Heo, Q. V. Ly, Q. T. Trinh, M. Shokouhimehr, C. Xia, S. S. Lam, D.-V. N. Vo, S. Y. Kim, Q. Van Le, J. Clean. Prod. 2020, 270, 121912. [3] C. L. Bianchi, C. Pirola, E. Selli, S. Biella, J. Hazard. Mater. 2012, 211-212, 203. [4] C. L. Bianchi, G. Cerrato, C. Pirola, F. Galli, V. Capucci, Environ. Sci. Pollut. Res. 2019, 26, 36117.