H‐Doped Black Titania with Very High Solar Absorption and Excellent Photocatalysis Enhanced by Localized Surface Plasmon Resonance

Abstract

Black TiO2 attracts enormous attention due to its large solar absorption and induced excellent photocatalytic activity. Herein, a new approach assisted by hydrogen plasma to synthesize unique H‐doped black titania with a core/shell structure (TiO2@TiO2‐xHx) is presented, superior to the high H2‐pressure process (under 20 bar for five days). The black titania possesses the largest solar absorption (≈83%), far more than any other reported black titania (the record (high‐pressure): ≈30%). H doping is favorable to eliminate the recombination centers of light‐induced electrons and holes. High absorption and low recombination ensure the excellent photocatalytic activity for the black titania in the photo‐oxidation of organic molecules in water and the production of hydrogen. The H‐doped amorphous shell is proposed to play the same role as Ag or Pt loading on TiO2 nanocrystals, which induces the localized surface plasma resonance and black coloration. Photocatalytic water splitting and cleaning using TiO2‐xHx is believed to have a bright future for sustainable energy sources and cleaning environment.

Black Titanium Dioxide Nanomaterials in Photocatalysis

“…Color change from white to black for TiO 2 nanomaterials reflects the change in optical properties and thus suggests the structural change after modification, at least the surface structural change. High-resolution transmission electron microscope (HRTEM) has revealed that a number of black TiO 2 nanomaterials have a crystalline/ amorphous core/shell structure, while white ones have clear lattice fringes throughout the crystals [22,23,[30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. The amorphous or disordered surface layer has been considered the typical feature of black TiO 2 nanomaterials.…”

Influence of annealing atmosphere on formation of electrically-active defects in rutile TiO2

“…19,20,23,24 This can, for example, be observed in the case of H i : Conductivity, transport, electron paramagnetic resonance, and infrared absorption measurements report on a shallow donor level with thermal transition energies of several meV, 10,11,25,[30][31][32] while absorption data indicate optical transition energies of around 1-2 eV. 8,28,32,33 Another prominent example is V O . Some experiments indicate that V O is a shallow donor in rutile TiO 2 , responsible for the n-type conductivity observed in samples annealed at low oxygen partial pressure, 13,14,34 while other studies report V O -related deep states.…”

“…6 Recently, reduced and/or hydrogenated TiO 2 has received increasing interest because it exhibits stronger absorption in the visible/infrared wavelength regime than virgin rutile TiO 2 . 7,8 However, the understanding of intrinsic and impurity-related defects in this material is not fully developed to date, but it is of key importance in virtually all of its applications.…”

Hydrogenated TiO2/SrTiO3 porous microspheres with tunable band structure for solar-light photocatalytic H2 and O2 evolution

“…In this context, H2 and O2 have attracted remarkable interest as promising energy carriers as they do not produce the greenhouse gas CO2 [3,4]. The synergistic effects of the two related half-reactions, i.e., photoinduced electron reduction and hole oxidation, are very important for H2 and O2 evolution from water splitting, and inherently determine photocatalysis efficiency [5].…”