Visible-light photocatalytic, solar thermal and photoelectrochemical properties of aluminium-reduced black titania

Abstract

Utilizing solar energy for hydrogen generation and water cleaning is a great challenge due to insufficient visible-light power conversion. Here we report a mass production approach to synthesize black titania by aluminium reduction. The obtained sample possesses a unique crystalline core-amorphous shell structure (TiO 2 @TiO 2Àx ). The black titania absorbs $65% of the total solar energy by improving visible and infrared absorption, superior to the recently reported ones ($30%) and pristine TiO 2 ($5%). The unique core-shell structure (TiO 2 @TiO 2Àx ) and high absorption boost the photocatalytic water cleaning and water splitting.The black titania is also an excellent photoelectrochemical electrode exhibiting a high solar-to-hydrogen efficiency (1.7%). A large photothermic effect may enable black titania "capture" solar energy for solar thermal collectors. The Al-reduced amorphous shell is proved to be an excellent candidate to absorb more solar light and receive more efficient photocatalysis.

Hydrogen-Etched TiO2−x as Efficient Support of Gold Catalysts for Water–Gas Shift Reaction

“…Then, valence band spectra of TiO 2 -N and TiO 2−x -N were measured, and the valence band maximum (VBM) almost locates a similar value (1.99 eV below the Fermi energy, Figure 8b), consistent with the reported results [53]. Due to the same VBM, the above-mentioned decrease of E g value should be ascribed to the decrease of the conduction band minimum (CBM).…”

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.…”

“…It was proposed that improved photocatalytic performance of slightly hydrogenated TiO 2 could be attributed to the higher ratio of trapped holes (O − centers) and a lower recombination rate induced by the increase of surface defects, while the highly concentrated bulk defects in gray and black (overhydrogenated) TiO 2 acted as charge recombination centers, leading to worse photoactivity [57]. Huang's group has reported on the synthesis of a series of black TiO 2 nanomaterials by aluminum reduction [9,32,37,38,41,53]. The typical crystalline/amorphous core/shell structure was observed in almost all Al-reduced black TiO 2 [9,32,37,38,41], except for the black TiO 2 nanotubes [53].…”

“…Oxygen vacancies are undetectable in most white TiO 2 nanomaterials, while oxygen vacancy is considered to be one of the feature defects in most black TiO 2 nanomaterials. Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscope [37][38][39][40]52], Raman spectroscope [9,16,32,[53][54][55], and X-ray diffractometer [23,32,55] [30,33,37,41,52,55,57,59,60].…”

Sub-10 nm rutile titanium dioxide nanoparticles for efficient visible-light-driven photocatalytic hydrogen production

“…Self-doping with Ti 3 þ was further developed for narrowing the band of TiO 2 without the introduction of unwanted carrier recombination centres from dopants [19][20][21] , which consequently exhibited good stability and considerable activity for photocatalytic hydrogen production under visible light 20,21 . Recently, hydrogenation of crystalline TiO 2 was disclosed as a new approach to enhance the visible as well as infrared light absorption of pristine TiO 2 and subsequently triggered great interest [22][23][24][25][26][27][28] . The surface disorder of hydrogenated black TiO 2 , instead of bulk Ti 3 þ , was proposed to be responsible for the extended light absorption 23,24 .…”