Enhanced Photocatalysis from Truncated Octahedral Bipyramids of Anatase TiO₂ with Exposed {001}/{101} Facets

Abstract

In this study, we develop a new synthetic method to grow anatase TiO 2 crystals composed of truncated octahedral bipyramids (TOBs) with exposed {001} and {101} facets by a vapor–solid reaction growth (VSRG) method. The VSRG method employs TiCl 4(g) to react with CaO (s) /Ca(OH) 2(s) at 823–1043 K under atmospheric pressure. The O-deficient pale-blue TOB TiO 2 crystals display high amount of both {001} and {101} facets. Together, they decompose methylene blue photocatalytically under UV–visible (UV–vis) light irradiation. The most-efficient TOB catalyst VT923 (grown at 923 K, average edge length 400 nm, average thickness 200 nm, and surface area 4.20 m 2 /g) shows a degradation rate constant k , 0.0527 min –1 . This is close to that of the P25 standard 0.0577 min –1 . However, the surface area of P25 (46.8 m 2 /g) is about 12 times that of VT923. The extraordinary performance of VT923 is attributed to the presence of high amount of coexisting {001} and {101} facets to form effective surface heterojunctions. They would separate photogenerated electrons and holes effectively on {101} and {001} surfaces, respectively. For VT923, the {001}/{101} ratio is 0.764, which is close to 1, the highest value observed for all TOB samples grown in this study. The surface heterojunctions prolong the electron–hole separation so that VT923 demonstrates the excellent photocatalytic capability. In addition, residual Cl atoms on the exposed faces are easily removed to show clean TiO surface layers with sufficient amount of O-deficient sites in the current samples.

Enhanced Visible Light Photocatalytic Activity of N and Ag Doped and Co-Doped TiO2 Synthesized by Using an In-Situ Solvothermal Method for Gas Phase Ammonia Removal

“…As shown in the survey XPS spectra in Figure 4a and all the doped TiO 2 samples displayed the same survey XPS spectra of signals from Ti and O atoms as undoped TiO 2 , which was related to Ti-O bonds in a TiO 2 crystal lattice . The C 1s contaminant located at around 284.4-284.8 eV was also found in all samples, which was mostly ascribed to organic precursors [41]. The additional signals from N and Ag were observed in survey scan XPS spectra of the doped materials.…”

“…Therefore, the alteration in crystallite size and lattice strain could also confirm that every amount of N and Ag loading by using an in-situ solvothermal synthesis were successfully introduced into a TiO2 crystal lattice, which was the main factor effected on the modification of TiO2 crystallinity [14,33]. Several studies [39][40][41] have reported that the crystal structure and crystallite size of the photocatalyst play an important role on the photocatalytic activity performance.…”

Facile Formation of Anatase/Rutile TiO2 Nanocomposites with Enhanced Photocatalytic Activity

“…After that, Yang et al reported that single crystals with a high percentage of exposed {001} facets were synthesized by using hydrofluoric acid as the morphology control agent [18]. Lee et al reported that truncated octahedral anatase bipyramids with exposed {001} and {101} facets were synthesized by a vapor-solid reaction growth method [19]. Recently, {101}-oriented rutile TiO 2 nanorods were prepared under hydrothermal conditions, which exhibited efficient solar water-splitting performance [20].…”

Vapor–Solid Reaction Growth of Rutile TiO2 Nanorods and Nanowires for Li-Ion-Battery Electrodes

“…An analogous reaction route, reported previously by our group, was employed. 17 In the process, CaO (s) was reacted with TiCl 4(g) using the same reaction setup under similar conditions. The dark blue products, C923, C973, and C1024, obtained from the reactions carried out at 823, 973, and 1024 K, respectively, were collected (Table S1).…”

“…Even though the process is an improvement of a previously reported VSRG route, to our knowledge, the observation is the first report of rutile TiO 2 in this morphology. 17 The as-prepared TiO 2(s) NRs and NWs structures are O-deficient and show excellent electrochemical behavior as the anode material in LIBs.…”