Synthesis and Characterization of Enhanced Photocatalytic Activity with Li⁺-Doping Nanosized TiO₂ Catalyst

Abstract

The photocatalytic efficiency of TiO2 is reduced by rapid electron–hole recombination. An effective approach to address this limitation is to have TiO2 doped with various metal ions or heteroatoms. Herein, we prepared a series of Li+-doped TiO2 nanoparticles showing high photocatalytic activities through the sol–gel method. The samples were characterized by X-ray diffraction (XRD) and surface area analyses. Effects of Li+ doping on the Brunauer–Emmett–Teller (BET) surface area, crystallite size, phase transformation temperature, and phase composition were studied. The results showed that Li+ doping can promote the generation of the rutile crystal phase in TiO2, lower the anatase-to-rutile transformation temperature, and generate the mixed-crystal effect. The photocatalytic degradation of methyl orange (MO) was used as a probe reaction to evaluate the photoactivity of the nanoparticles. Parameters affecting the photocatalytic efficiency, including the Li+ doping amount, calcination temperature, and catalyst amount, as well as the kinetics of the photocatalytic process toward the degradation of MO, were investigated. The mixed-crystal TiO2, which was doped with 1.0 mol % Li+ and calcined at 550 °C containing 27.1% rutile and 72.9% anatase phase, showed a 2.2-fold increase in the photoactivity on the basis of the rate constant of MO decomposition as compared with the undoped TiO2. The existence of a definite quantity of rutile phase could effectively inhibit the recombination of the electron–hole pairs, thus promoting photocatalytic activity.

All-Liquid-Phase Reaction Mechanism Enabling Cryogenic Li–S Batteries

“…By fitting the charge transfer resistance (R CT ) measured at different temperatures into the Arrhenius equation, the E a at different discharging states can be obtained (Figures S13, S14, and 4c). 34,35 Overall, the resulting E a is summarized in Figure 4d. No significant change of E a can be obtained for conventional electrolytes during the stages from A to C (corresponding to the long-chain-polysulfide-forming step).…”

Enhanced Catalytic Activity of a Vanadium-Doped Mesoporous Octahedral Molecular Sieve-2 (K-OMS-2) toward Hydrogen Evolution Reaction

“…The V 2p 3/2 peak at ∼516.2 eV (Figure ) with a spin–orbit splitting value of ∼7.4 confirms that the vanadium has a 4+ oxidation state. Since the ionic radius of V 4+ is 0.72 A° (< 0.92 A°), according to Pauling’s coordination principle, the V 4+ was not incorporated in the tunnel sites but incorporated into the framework …”

“…Since the ionic radius of V 4+ is 0.72 A°(< 0.92 A°), according to Pauling's coordination principle, the V 4+ was not incorporated in the tunnel sites but incorporated into the framework. 40 4.2. Effect of V Doping into the K-OMS-2 Framework.…”

Microflowery, Microspherical, and Fan-Shaped TiO2 Crystals via Hierarchical Self-Assembly of Nanorods with Exposed Specific Crystal Facets and Enhanced Photocatalytic Performance

“…Among the five TiO 2 samples, AS-TiO 2 showed the highest photocatalytic activity, which can be attributed to its anatase phase structure and relatively high specific surface area. The relatively high photocatalytic activity of CM-TiO 2 can be attributed to the different energy band structures of anatase (96.8%) and rutile (3.2%), because the photogenerated electrons transfer from rutile to anatase, whereas the photogenerated holes transfer from anatase to rutile, which can inhibit the charge recombination of the photogenerated electron-hole pairs, thereby enhancing the photocatalytic activity [45,46]. No-TiO 2 and urea-TiO 2 delivered the lower photocatalytic activity with a degradation efficiency of 38.1% and 35.5%, respectively, because these two samples consisted only of single rutile and had smaller specific surface areas (No-TiO 2 : 2.58 m 2 /g; urea-TiO 2 : 4.71 m 2 /g).…”