10.1021/acs.jpclett.5b02219.s001 Manjula I. Nandasiri Manjula I. Nandasiri Vaithiyalingam Shutthanandan Vaithiyalingam Shutthanandan Sandeep Manandhar Sandeep Manandhar Ashleigh M. Schwarz Ashleigh M. Schwarz Lucas Oxenford Lucas Oxenford John V. Kennedy John V. Kennedy Suntharampillai Thevuthasan Suntharampillai Thevuthasan Michael A. Henderson Michael A. Henderson Instability of Hydrogenated TiO<sub>2</sub> American Chemical Society 2015 bulk diffusivity Hydrogenated TiO 2Hydrogenated TiO 2 Similar anneals photoelectron spectroscopy nm 473 K 373 K reaction analysis rutile light photocatalyst surface 523 K NRA 2015-11-11 05:03:17 Journal contribution https://acs.figshare.com/articles/journal_contribution/Instability_of_Hydrogenated_TiO_sub_2_sub_/2005401 Hydrogenated TiO<sub>2</sub> (H-TiO<sub>2</sub>) is touted as a viable visible light photocatalyst. We report a systematic study on the thermal stability of H-implanted TiO<sub>2</sub> using nuclear reaction analysis (NRA), Rutherford backscattering spectrometry, ultraviolet photoelectron spectroscopy, and X-ray photoelectron spectroscopy. Protons (40 keV) implanted at a ∼2 atom % level within a ∼120 nm wide profile of rutile TiO<sub>2</sub>(110) were situated ∼300 nm below the surface. NRA revealed that this H-profile broadened toward the surface after annealing at 373 K, dissipated out of the crystal into vacuum at 473 K, and was absent within the beam sampling depth (∼800 nm) at 523 K. Photoemission showed that the surface was reduced in concert with these changes. Similar anneals had no effect on pristine TiO<sub>2</sub>(110). The facile bulk diffusivity of H in rutile at low temperatures, as well as its interfacial activity toward reduction, significantly limits the utilization of H-TiO<sub>2</sub> as a photocatalyst.