Construction of the Rutile/Anatase Micro-Heterophase Junction Photocatalyst from Anatase by Liquid Nitrogen Quenching Method

Abstract

Heterophase junction composite semiconductors have been documented to exhibit better photocatalytic activity than the corresponding single-phase semiconductors for chemical reactions such as the hydrogen evolution and the degradation of pollutants. However, how to further improve the photocatalytic activity of these materials is a great challenge from the perspective of theory and practice. Herein, we report the synthesis of the rutile/anatase micro-heterophase junction from nanoscale anatase TiO 2 by a rapid thermal treatment followed by liquid nitrogen quenching (RQ). The RQ micro-heterophase junction sample showed excellent photocatalytic hydrogen evolution activity, which has 4−5 times higher hydrogen production rate than that of nude anatase and P25-TiO 2 , and 2 times better hydrogen production rate than the anatase/rutile TiO 2 heterophase sample with comparable Brunauer−Emmett−Teller (BET) surface area and phase composition obtained through slow thermal treatment and natural cooling (SN) process. The enhanced photocatalytic capacity of the RQ sample is attributed to the formation of a rutile/anatase micro-heterophase junction and its modification of the heterophase interface in the treatment process. Especially, the RQ-TiO 2 sample shows a stronger electron paramagnetic resonance (EPR) signal of Ti 3+ than the pristine anatase, rutile TiO 2 , and SN-TiO 2 , implying the formation of Ti 3+ ions at the interface between anatase and rutile components. This results in moving down the Fermi level of the rutile phase by 330 meV. This increases the Fermi level difference between anatase and rutile, increases the build-in electric field (BIEF) of the anatase/rutile heterophase junction, and the separation as well as the transfer of photogenerated charge carriers more effective through the rutile/anatase heterophase interface. This work provides not only a facile method for the preparation of the rutile/anatase micro-heterophase junction from anatase but also finds a pathway to regulate the BIEF with a self-doped low-valence metal ion.

Photo-Thermo Catalytic Oxidation of C₃H₈ and C₃H₆ over the WO₃-TiO₂ Supported Pt Single-Atom Catalyst

“…In the presence of oxygen, the signals assigned to oxygen vacancy (g = 2.003) and Ti 3+ centers in the anatase TiO2 (g = 1.990) are identified on the Pt1/WO3-TiO2 in the dark (Fig. S11) 33,42,43 . Upon the light illumination, the additional EPR signals (gxx = 2.017, gyy = 2.012, gzz = 2.002) appear, which can be allocated to the surface trapped hole centers O3…”

Engineering interface structures for heterojunction photocatalysts

“…CO adsorption in-situ infrared experiment, isotope tracing experiment and quantitative calculation showed that this unique Pt-TiO 2 interface structure enabled the CO adsorbed on Pt to be oxidized by adjacent holes. Wang et al 18 also reported that rutile/anatase heterophase junctions were prepared by rapid heat treatment combined with liquid nitrogen quenching of nanoscale anatase TiO 2 (Fig. 9(E)).…”

“…13,14 By constructing a heterojunction structure, a built-in electric field is generated at the heterojunction interfaces, which can spontaneously orient and expedite the transfer of photogenerated electrons from one semiconductor to the other and the transfer of holes toward the opposite direction and also could greatly reduce the recombination of photogenerated electrons and holes in the transfer process from bulk towards the surface. A good deal of heterocomposites, including those with p–n heterojunction structures, 13 Z-scheme structures, 15,16 Schottky junction structures, 17 and heterophase junction structures, 18,19 have been reported as active photocatalysts for various energy and environment reactions. Many reviews have summarized heterojunction photocatalysts and their applications.…”

Light-Excited Ag-Doped TiO2−CoFe2O4 Heterojunction Applied to Toluene Gas Detection

“…From the XRD test results in Figure 1a, the typical anatase peak pattern of TiO 2 can be seen; the peaks appearing at 2θ = 25.347 [30,31]. When compared to other peaks, the intensity of the peak at 25.347 • is the highest, indicating that the corresponding (101) crystal plane is the most exposed.…”