Synthesis of Efficient Nanosized Rutile TiO₂ and Its Main Factors Determining Its Photodegradation Activity: Roles of Residual Chloride and Adsorbed Oxygen

Abstract

Nanosized TiO 2 containing different contents of rutile phase was controllably synthesized by a hydrochloric acid-modified hydrothermal process. It is demonstrated that the formation of rutile phase in TiO 2 mainly depends on the role of chlorine anions in the synthesis, and a certain amount of residual chloride would exist on the surfaces of the resulting nanocrystalline rutile TiO 2 . Interestingly, the as-prepared rutile shows high activity for photodegradation of rhodamine B dye compared with the as-prepared anatase, even superior to the P25 TiO 2 . It is mainly attributed to the residual chloride that could promote the dye adsorbed on the surfaces of TiO 2 , consequently accelerating the photosensitization oxidation reactions of the dye molecules. In the photodegradation of liquidphase phenol and gas-phase aldehyde, the as-prepared rutile TiO 2 samples display low activity, which is attributed to the photogenerated electrons weakly captured by the adsorbed oxygen, since the residual chloride could effectively capture photoinduced holes based on the atmosphere-controlled surface photovoltage spectroscopy results. Further, the photoactivity of resulting rutile for degrading phenol and aldehyde is greatly enhanced by modifying a proper amount of phosphoric acids to increase the adsorption of O 2 , even higher than that of the P25 TiO 2 . This work would explore feasible routes to synthesize efficient nanosized rutile TiO 2 -based photocatalysts for degrading colored and colorless organic pollutants by investigating the rate-determining factors in the photodegradation processes.

Highly photocatalytic activity of brookite/rutile TiO2 nanocrystals with semi-embedded structure

“…The photocatalytic activity of TiO 2 can be influenced by many factors such as crystal structure, particle size, surface morphology, and porosity [6][7][8][9][10][11], with crystal structure being the major factor in photocatalytic performance [7,10,12]. Many researchers have discussed the intrinsic connection between crystal phase and photocatalytic activity [13][14][15][16][17][18]. Of the two most common TiO 2 crystal phases (anatase and rutile), anatase has the greater photoactivity [19].…”

Enhanced efficiency in flexible dye-sensitized solar cells by a novel bilayer photoanode made of carbon nanotubes incorporated TiO 2 nanorods and branched TiO 2 nanotubes

“…Hence, the hydrothermal process of the TCNFs in HCl aqueous solution is similar to the TNFs in HCl aqueous solution. Until now, many studies concerning the hydrothermal treatment of crystalline TiO 2 with HCl aqueous solutions have been reported [36][37][38][39][40]. Among these studies, although some debate on the formation mechanism of the crystallite phase and the morphology of the products is still under discussion, the consensuses can be summed up as follows: (1) The rutile TiO 2 can be obtained with the high concentration of HCl hydrothermal treatment; (2) the selective adsorption of Cl À ions on the (110) plane of rutile TiO 2 nucleus guides anisotropic one dimensional growth along the [001] orientation.…”

“…Besides, the TiO 2 embedded into the carbon matrix and the stable carbon impedes the ingrowth of the rutile TiO 2 . The rutile TiO 2 grows outside along the [001] orientation due to Cl À ions [36][37][38][39][40]. In the meanwhile, the TiO 2 NPs inside the TCNFs gradually transfer outside as a part of the NRs on the surface of TCNFs.…”

Enhanced visible-light activities for PEC water reduction of CuO nanoplates by coupling with anatase TiO2 and mechanism

“…The photoelectrodes were illuminated with a 500 W Xenon lamp to produce a visible light source with an intensity of 64 mW/cm 2 after utilizing a filter to remove light below the wavelength of 420 nm [15]. The steady-state surface photovoltage spectra (SS-SPS) instrument was a home-built apparatus as discussed elsewhere [20]. [16,21].…”

“…The SS-SPS measurement, with a very high sensitivity, is a well-suitable and direct method to reveal the properties of photogenerated charges of solid semiconducting materials, and the strong SPS signal frequently corresponds to the high photogenerated charge separation [20,25]. In order to investigate the capturing processes for photogenerated charges, we have completed the atmosphere-controlled SPS measurements, and the SPS response greatly depends on the O 2 concentration.…”