Introduction of atom vacancies and heteroatom dopants have been widely used to improve their visible-light responding photocatalytic activities [1, 2]. However, it always results in limited visible-light absorption increase, like an extra absorption shoulder or up-shifted absorption tail, coming from the accompanying donor electrons filling the donor states beneath the conduction band or the narrow newly-formed energy level above the conduction band. To improve the visible-light absorption further, we developed a methodology of introducing hydrogen-mediated anion vacancies. Taking TiO2 as an example, theoretical simulations and experimental results showed that the introduced atomic H-mediated oxygen vacancies (OVH) could induce a sub-valence band of certain width within the bandgap of TiO2, and bring about an unusual strong absorption band ranging across the full spectrum of visible light, with the bandgap of TiO2 decreasing from 3.2 eV to 1.98 eV. Compared with conventional blue-colored oxygen-vacancy-containing TiO2, OVH-TiO2 showed much higher photoelectrochemical current. This successful trial in TiO2 sheds new light on the modification of solar-conversion materials.
 Zuo, F., Wang, L., Wu, T., Zhang, Z., Borchardt, D., Feng, P. Self-Doped Ti3+ Enhanced Photocatalyst for Hydrogen Production under Visible Light. Journal of the American Chemical Society, 132, 11856-11857 (2010).
 Asahi, R., Morikawa, T., Ohwaki, T., Aoki, K., Taga, Y. Visible-light photocatalysis in nitrogen-doped titanium oxides. Science, 293, 269-271(2001).
 Yang, Y. Q., Yin, L.-C., Gong, Y., Niu, P., Wang, J. Q., Gu, L., Liu, G., Wang, L. Z., Cheng, H.-M., An Unusual Strong Visible-light Absorption Band in Anatase TiO2 Photocatalyst induced by Atomic Hydrogen-occupied Oxygen Vacancies. Advanced Materials, accepted.