Incorporation of Non-metal Impurities at the Anatase TiO$_2$(001)-(1 $\times$ 4) Surface

Surface doping of TiO$_2$ is of special interest because the distribution of impurities at or near the surface can have a significant influence on the photocatalytic properties of TiO$_2$. We have used first-principles density functional theory (DFT) calculations to determine the incorporation mechanisms of nitrogen (N) and carbon (C), two widely used $p$-type dopants, at the reconstructed (001) surface of anatase, the TiO$_2$ polymorph most relevant for photocatalysis. Starting from adsorbed impurities, we identify various incorporation pathways and show that the non-exposed oxygen sites just below the surface play a crucial role in accomodating non-metal impurities at the TiO$_2$(001) surface. Based on the obtained results, we propose strategies which could help to increase the doping concentration and the photocatalytic activity at the TiO$_2$ surface by exploiting the morphology of the reconstructed surface [1].\\[4pt] [1] Incorporation of Non-metal Impurities at the Anatase TiO$_2$(001)-(1 $\times$ 4) Surface, \underline {arXiv:1209.1602}.