Abstract
Defect engineering in photocatalysts recently exhibits promising performances in solar-energy-driven reactions. However, defect engineering techniques developed so far rely on complicated synthesis processes and harsh experimental conditions, which seriously hinder its practical applications. In this work, we demonstrated a facile mass-production approach to synthesize gray titania with engineered surface defects. This technique just requires a simple liquid-plasma treatment under low temperature and atmospheric pressure. The in situ generation of hydrogen atoms caused by liquid plasma is responsible for hydrogenation of TiO2. Electron paramagnetic resonance (EPR) measurements confirm the existence of surface oxygen vacancies and Ti3+ species in gray TiO2−x. Both kinds of defects concentrations are well controllable and increase with the output plasma power. UV–Vis diffused reflectance spectra show that the bandgap of gray TiO2−x is 2.9 eV. Due to its extended visible-light absorption and engineered surface defects, gray TiO2−x exhibits superior visible-light photoactivity. Rhodamine B was used to evaluate the visible-light photodegradation performance, which shows that the removal rate constant of gray TiO2−x reaches 0.126 min−1 and is 6.5 times of P25 TiO2. The surface defects produced by liquid-plasma hydrogenation are proved stable in air and water and could be a candidate hydrogenation strategy for other photocatalysts.
Highlights
Titanium dioxide (TiO2) due to its nontoxic, high stability, and high photocatalytic performance is considered as a promising photocatalyst, which has been widely used in environmental remedies and water splitting [1,2,3]
The stabilities of surface oxygen defects, as well as photodegradation performance exhibited in gray TiO2−x, which confirms that the mechanism of plasma power-related hydrogenation with TiO2 plays the major role in whole synthesis procedure
A simple green method assisted by liquid plasma has been demonstrated for the synthesis of gray TiO2−x at a low temperature and atmospheric pressure
Summary
Titanium dioxide (TiO2) due to its nontoxic, high stability, and high photocatalytic performance is considered as a promising photocatalyst, which has been widely used in environmental remedies and water splitting [1,2,3]. It is significant and desirable to develop a simple and feasible strategy for massive production of black/gray TiO2−x with engineered surface defects and related abundant solar absorption. We conduct a one-pot synthesis of gray TiO2−x with large solar harvesting and engineered surface defects using a liquid-plasma technology at room temperature and atmospheric pressure [25]. There has recently been increasing interest in liquid-plasma discharges and their potential applications in various technologies, including environmental remediation, nanomaterial synthesis, and surface processing [26,27,28]. We hypothesize that white TiO2 nanoparticles dissolved in electrolyte entered the hot plasma area, and underwent plasma thermal treatment and hydrogenation at/near the plasma region FigurFeig2u.reT2h.eTshyenstyhnetshiessmis emcehcahnainsimsmooffggrraayy TTiiOO222−−−xxxnnananosopshpehreeraessaisstseidstebdy bliyquliidqupildasmplaasamnda tahned the correcsoprorensdpionngdoinpgtiocpatliceaml eimssiisosniosnpsepcetcrturummoorriiggiinnaatteedd ffrroommccaaththooddicicTiTeileecletrcotdroesd.es
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