Facile One-Step Route for the Development of in Situ Cocatalyst-Modified Ti³⁺ Self-Doped TiO₂ for Improved Visible-Light Photocatalytic Activity

Abstract

Development of visible-light-driven photocatalysts by employing a relatively simple, efficient, and cost-effective one-step process is essential for commercial applications. Herein, we report for the first time the synthesis of in situ Cu-ion modified Ti self-doped rutile TiO by such a facile one-step solution precursor plasma spray (SPPS) process using a water-soluble titanium precursor. In the SPPS process, Ti self-doping on Ti of rutile TiO is found to take place because of electron transfer from the created oxygen vacancies to Ti-ions. In situ Cu modification of the above Ti self-doped rutile TiO by additionally introducing a Cu solution into plasma plume is also demonstrated. While the Ti self-doping induces broad absorption in the visible-light region, the addition of Cu ion leads to even broader absorption in the visible region owing to resulting synergistic properties. The above materials were evaluated for various self-cleaning photocatalytic applications under visible-light illumination. Cu-ion modified Ti self-doped rutile TiO is noted to exhibit a remarkably enhanced visible-light activity in comparison with Ti self-doped rutile TiO, with the latter itself outperforming commercial TiO photocatalysts, thereby suggesting the suitability of the material for indoor applications. The broad visible-light absorption by Ti self-doping, the holes with strong oxidation power generated in the valence band, and electrons in Ti isolated states that are effectively separated into the high reductive sites of Cu ions upon visible-light irradiation, accounts for improved photocatalytic activity. Moreover, the synthesis process (SPPS) provides a valuable alternative to orthodox multistep processes for the preparation of such visible-light-driven photocatalysts.

Effects of Particle Size on the Structure and Photocatalytic Performance by Alkali-Treated TiO2

“…As displayed in Figure 4a, the pristine TiO 2 shows a strong absorption in ultraviolet region and the absorption edge is located at 400 nm, which is consistent with the light absorption characteristics of anatase TiO 2 [46]. For TiO 2 -X, it exhibits increased absorption in the region of 200-800 nm after hydrothermal treatment, which can be attributed to surface oxygen vacancies and Ti 3+ [44,47]. According to the Kubelka-Munk function, the band gap energies can be calculated from the plots of (αhv) 1/2 versus photon energy [43].…”

“…This also demonstrates that the morphology of the nanomaterial has a certain influence on its photocatalytic effect. 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 increased absorption in the region of 200-800 nm after hydrothermal treatment, which can be attributed to surface oxygen vacancies and Ti 3+ [44,47]. According to the Kubelka-Munk function, the band gap energies can be calculated from the plots of (αhv) 1/2 versus photon energy [43].…”

Highly Efficient Visible Light Catalysts Driven by Ti3+‐VO‐2Ti4+‐N3− Defect Clusters

“…However, the results are not consistent. Some researchers reported that the incorporation of N 3− or Ti 3+ ions significantly enhanced VLC efficiency [6,15–17 ] while others found that they were only slightly effective or even completely ineffective ,. Furthermore, the mechanisms underlying VLC effects are also ambiguous.…”

“…Furthermore, the mechanisms underlying VLC effects are also ambiguous. The formation of isolated states between forbidden bands,, multiple light reflections from material hierarchical structures, the introduction of oxygen vacancies, the optical intragap absorption, as well as the appearance of a diamagnetic cluster were all suggested as potential mechanisms for those observed photocatalytic phenomena. From a structural perspective, the incorporation of N 3− or Ti 3+ ions will concurrently introduce oxygen vacancies into TiO 2 for charge balance and then inevitably deteriorate photocatalytic performances through forming “recombination centers” to trap photo‐excited carriers.…”

In situ preparation of oxygen-deficient TiO2 microspheres with modified {001} facets for enhanced photocatalytic activity

“…Recently, reduced TiO 2 containing the Ti 3+ or oxygen vacancy has been demonstrated to extend the light absorption spectrum and enhance the electron mobility as well as electron-hole separation efficiency. [22][23][24] Different strategies, such as H 2 /Ar treatment 25 and laser irradiation, 26 as well as metal reduction methods using Al, 27 Zn 28 and Mg, 29 were used to prepare Ti 3+doped or oxygen-vacancy-rich TiO 2 . Although progress has been achieved using these methods, they are rather time-consuming, not environmentally friendly and are energy wasteful.…”