Semiconductor photocatalysis could be an effective means to combat air pollution, especially nitrogen oxides, which can be mineralized to nitrate. However, the reaction typically shows poor selectivity, releasing a number of unwanted and possibly toxic intermediates such as nitrogen dioxide. Up to now, the underlying principles that lead to this poor selectivity were not understood so a knowledge-based catalyst design for more selective materials was impossible. Herein, we present strong evidence for the slow oxygen reduction being one the causes, as the competing back-reduction of nitrate leads to the release of nitrogen dioxide. Consequently, engineering the photocatalyst for a better oxygen reduction efficiency should also increase the nitrate selectivity.
Patzsch, J., Folli, A., Macphee, D., & Bloh, J. Z. (2017). On the Underlying Mechanisms of the Low Observed Nitrate Selectivity in Photocatalytic NOx Abatement and the Importance of the Oxygen Reduction Reaction. Physical Chemistry Chemical Physics, 48(19), 32678-32686 . https://doi.org/10.1039/C7CP05960D