Photocatalytic Reduction Activity Research Articles

Nitrate Reduction in Water Using Commercial Titanium Dioxide Photocatalysts (P25, P90, and Hombikat UV100)

AbstractPhotocatalytic nitrate reduction was examined in a model water and in groundwater by using three commercially available titanium dioxide photocatalysts (Evonik P25, Evonik P90, and Sachtleben Hombikat UV100). The photocatalysts were characterized using uniform methods (TEM, XRD, surface area, UV-VIS, surface charge) and their photocatalytic activity was differentiated using these results. Under all experimental conditions, P25 and P90 were superior to UV100, and P90 outperformed P25 with nitrate reductions as high as 77% at the maximum irradiance level used (6.46×1022 photons/L). The photocatalytic nitrate reduction activity was found to be dependent on the rate of recombination, pH, and the total photocatalyst surface area, with the recombination rate being the limiting variable. Nitrate reduction was more efficient in model water than in groundwater that contained constituents capable of occupying photocatalyst surface sorption sites or scavenging conduction band electrons. The greater efficien...

UV-assisted photocatalytic synthesis of ZnO–reduced graphene oxide composites with enhanced photocatalytic activity in reduction of Cr(VI)

ZnO–reduced graphene oxide (RGO) composites are successfully synthesized via UV-assisted photocatalytic reduction of graphite oxide by ZnO nanoparticles in ethanol. Their morphology, structure and photocatalytic performance in reduction of Cr(VI) are characterized by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction spectroscopy, UV–vis absorption spectrophotometer, respectively. The results show that in the composites the RGO nanosheets are decorated densely by ZnO nanoparticles, which displays a good combination between RGO and ZnO. ZnO–RGO composites exhibit an enhanced photocatalytic performance in reduction of Cr(VI) with a maximum removal rate of 96% under UV light irradiation as compared with pure ZnO (67%) due to the increased light absorption intensity and range as well as the reduction of electron–hole pair recombination in ZnO with the introduction of RGO.

Titanium dioxide–gold nanocomposite materials embedded in silicate sol–gel film catalyst for simultaneous photodegradation of hexavalent chromium and methylene blue

Aminosilicate sol–gel supported titanium dioxide–gold (EDAS/(TiO 2–Au) nps) nanocomposite materials were synthesized by simple deposition–precipitation method and characterized. The photocatalytic oxidation and reduction activity of the EDAS/(TiO 2–Au) nps film was evaluated using hexavalent chromium (Cr(VI)) and methylene blue (MB) dye under irradiation. The photocatalytic reduction of Cr(VI) to Cr(III) was studied in the presence of hole scavengers such as oxalic acid (OA) and methylene blue (MB). The photocatalytic degradation of MB was investigated in the presence and absence of Cr(VI). Presence of Au nps on the (TiO 2) nps surface and its dispersion in the silicate sol-gel film (EDAS/(TiO 2–Au) nps) improved the photocatalytic reduction of Cr(VI) and oxidation of MB due to the effective interfacial electron transfer from the conduction band of the TiO 2 to Au nps by minimizing the charge recombination process when compared to the TiO 2 and (TiO 2–Au) nps in the absence of EDAS. The EDAS/(TiO 2–Au) nps nanocomposite materials provided beneficial role in the environmental remediation and purification process through synergistic photocatalytic activity by an advanced oxidation–reduction processes.

Photocatalytic Reduction of CO<sub>2</sub> to Methanol Using the InVO<sub>4</sub>-Based Photocatalysts

The InVO4-based photocatalysts loaded with metal oxides (Fe2O3, CuO, NiO) were synthesized by wet impregnation method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM), UV-vis diffuse reflectance spectroscopy(DRS). The influence of different metal oxides loading (Fe2O3, CuO, NiO) on the photocatalytic activity for photocatalytic reduction of CO2 was discussed. It is found that Fe2O3-loaded InVO4 significantly enhance the methanol yield through promoting the effective separation of photoinduced electron-hole pairs.

Phthalic acid modified TiO 2 and enhanced photocatalytic reduction activity for Cr(VI) in aqueous solution

The photocatalytic reduction of Cr(VI) on TiO 2 nanoparticle modified with phthalic acid, which was prepared through a chemisorption method, has been investigated under ultraviolet light irradiation. This study found that the adsorption of phthalic acid onto the surface of TiO 2 nanoparticle resulted in the formation of a surface-modified complex. The interaction of TiO 2 with phthalic acid was characterized by various spectroscopic methods including diffuse reflectance UV–vis, infrared, fluorescence spectra, and X-ray diffraction (XRD). The results indicated that the recombination of charge carriers was effectively suppressed due to the modification of phthalic acid on the surface of TiO 2. In addition, the modified TiO 2 resulted in enhanced photocatalytic reduction activity for Cr(VI), which might be attributed to the effective separation of electron–hole pairs.

Bismuth‐Doped Ordered Mesoporous TiO2: Visible‐Light Catalyst for Simultaneous Degradation of Phenol and Chromium

A controllable and reproducible synthesis of highly ordered two-dimensional hexagonal mesoporous, crystalline bismuth-doped TiO(2) nanocomposites with variable Bi ratios is reported here. Analyses by transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy reveal that the well-ordered mesostructure is doped with Bi, which exists as Bi(3+) and Bi((3+x+)). The Bi-doped mesoporous TiO(2) (ms-TiO(2)) samples exhibit improved photocatalytic activities for simultaneous phenol oxidation and chromium reduction in aqueous suspension under visible and UV light over the pure ms-TiO(2), P-25, and conventional Bi-doped titania. The high catalytic activity is due to both the unique structural characteristics and the Bi doping. This new material extends the spectral response from UV to the visible region, and reduces electron-hole recombination, which renders the 2.0% Bi-doped ms-TiO(2) photocatalyst highly responsive to visible light.

Preparation and Characterization of p-n Heterojunction Photocatalyst Cu2O / In2O3 and its Photocatalytic Activity under Visible and UV Light Irradiation

The photocatalyst was prepared from indium hydroxide calcined at for 3 h. The p-n heterojunction photocatalyst was prepared by ballmilling through doping into and using absolute alcohol as a disperser. The photocatalyst was characterized by X-ray powder diffraction, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, terephthalic acid photoluminescence probing technique, photoluminescence emission spectra, and transmission electron microscopy. The results showed that the photocatalytic activity of the was much higher than that of on the photocatalytic reduction of . However, the photocatalytic activity was much lower than that of on the photocatalytic oxidation of methylene blue. Namely, has higher photocatalytic reduction activity but lower photocatalytic oxidation activity. For the photocatalytic reduction of , the optimum amount of doped is 0.5 wt %. Compared with pure , the photoabsorption wavelength range of the photocatalyst redshifts and improves the utilization of the total spectrum. The effect of ballmilling time on the photocatalytic activity was investigated. The mechanisms of influence on the photocatalytic activity were also discussed by the p-n junction principle and the valance band theory.

A Room‐Temperature Reactive‐Template Route to Mesoporous ZnGa2O4 with Improved Photocatalytic Activity in Reduction of CO2

Mehr als ein Metall enthalten die mesoporösen Materialien MGa2O4 (M=Zn, Ni, Co), die durch Ionenaustausch aus kolloidalem mesoporösem NaGaO2 zugänglich sind (siehe Schema mit TEM-Bildern). Weil diese Vorstufe zugleich als Templat wirkt, spart man einen Templatentfernungsschritt ein.

A Room‐Temperature Reactive‐Template Route to Mesoporous ZnGa2O4 with Improved Photocatalytic Activity in Reduction of CO2

A Room‐Temperature Reactive‐Template Route to Mesoporous ZnGa₂O₄ with Improved Photocatalytic Activity in Reduction of CO₂

Preparation and activity evaluation of relative p–n junction photocatalyst Co-TiO2/TiO2

Co-TiO2 photocatalyst was prepared by a sol–gel method using Co(NO3)2 · 6H2O and tetrabutyl titanate [Ti(OC4H9)4] as raw materials, and Co-TiO2/TiO2 photocatalyst was synthesized by mixing the Co-TiO2 sol with TiO2 sol. The Co-TiO2/TiO2 was characterized by X-ray powder diffraction, UV–Vis diffuse reflection spectrum, scanning electron microscopy, transmission electron microscopy, fluorescence spectra and X-ray photoelectron spectroscopy. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic reduction of Cr2O7 2− and photocatalytic oxidation of methyl orange under UV irradiation. The results showed that, for the photocatalytic reduction of Cr2O7 2−, the optimum percentage of Co-doped for the Co-TiO2 was 0.5% (mole ratio of Co/Ti), and the optimum percentage of Co-TiO2 for the Co-TiO2/TiO2 was 2.0% (mole ratio of Co-TiO2/TiO2). The photocatalytic reduction activities of the Co-TiO2/TiO2 and Co-TiO2 are much higher than that of TiO2. However, the photocatalytic oxidation activities of the Co-TiO2/TiO2 and Co-TiO2 are much lower than that of TiO2. Effects of heat treatment on the photocatalytic activities of the Co-TiO2/TiO2 and Co-TiO2 were investigated. The mechanisms of influence on the photocatalytic activity were also discussed.

Preparation and Photocatalytic Activity Evaluation of Composite Photocatalyst Fe-TiO2/TiO2

Fe-TiO2 photocatalyst was prepared by Sol-gel method using tetrabutyl titanate [Ti(OC4H9)4] as the titanium precursor. The relative p-n junction composite Fe-TiO2/TiO2 samples were prepared by ball milling method. The structure and properties of the samples were characterized by XRD, DRS, XPS and PL emission spectra. The results show that doping Fe3+ into TiO2 is more beneficial to improve the photocatalytic reduction activity of the sample compared with the photooxidation activity. The optimum doping amount is 0.05% (Fe/Ti molar ratio) for the Fe-TiO2 photocatalyst. After coupled between Fe-TiO2 and TiO2, both the photooxidation and photoreduction activities of the sample are enhanced. It is proposed that as the formation of relative p-n junction between the Fe-TiO2 and TiO2, the photo-excited holes and electrons are separated effectively, and the photocatalytic activity is enhanced.

Two organic–inorganic hybrid compounds constructed from 12-tungstovanadate and bipyridine

Two rare 12-tungstovanadate-bipyridine inorganic–organic hybrid compounds, [VW12O40] · 2(4,4′-H2bipy) · 2H2O (1) and [VW12O40] · 4(2,2′-Hbipy) (2), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction and IR analysis. In 1, a 2-D supramolecular architecture is formed by hydrogen-bonding between [VW12O40]4− and bipy. Compound 1 shows good activity for photocatalytic reduction of rhodamine B in a liquid–solid system. The electrochemical and electrocatalytic properties of 2-bulk carbon paste electrode modified with 2 were investigated by cyclic voltammetry.

Study on the Photocatalytic Activity of <I>p</I>–<I>n</I> Junction Photocatalyst Cu<SUB>2</SUB>O/TiO<SUB>2</SUB>

p-n junction photocatalyst Cu2O/TiO2 was prepared by ball milling through doping Cu2O into TiO2 and using H2O solution as disperser. The p-n junction photocatalyst Cu2O/TiO2 was characterized by UV-Vis diffuse reflection spectrum, Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the photocatalyst was evaluated by photocatalytic reduction of Cr2O7(2-) and photocatalytic oxidation of methyl orange (MO), respectively. The results showed that, for the photocatalytic reduction of Cr2O7(2-), the optimum percentage of doped-Cu2O is 1.0% (weight percentage). The photoreduction activity of the p-n junction Cu2O/TiO2 is much higher than that of TiO2 on the photocatalytic reduction of Cr2O7(2-). However, the photooxidation activity of the p-n junction photocatalyst Cu2O/TiO2 is much lower than that of TiO2 on the photocatalytic oxidation of methyl orange (MO). Namely, the p-n junction photocatalyst Cu2O/TiO2 has higher photocatalytic reduction activity, but lower photocatalytic oxidation activity. Cu2O and TiO2 were coupled highly, forming the p-n junction Cu2O/TiO2 photocatalyst. The photocatalytic activity of the p-n junction Cu2O/TiO2 was discussed by the p-n junction principle. Effect of ball milling time on the photocatalytic activity of p-n junction photocatalyst Cu2O/TiO2 was also investigated.

A novel 12-tungstovanadate and 3d–4d heterometallic complex hybrid compound [V1W12O40][VO2Ag(phen)3

Abstract A novel organic–inorganic hybrid compounds containing 12-tungstovanadate and 3d–4d heterometallic complex, [V1W12O40][VO2Ag(phen)3]2 (1), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction and IR analysis. The complex is an uncommon bisupporting polyoxometalate derivative in which the saturated Keggin type polyoxoanions are covalently linked by bimetallic complex [VO2Ag(phen)3]2+. The neighboring Ag+ and V5+ cations are bridged by the oxo atom forming heterometallic cations with the Ag–V distances of 3.556(2) A in [VO2Ag(phen)3]2+ cations. Furthermore, the title compound shows good photocatalytic activity for reduction of Rhodamine B (RB) in a liquid–solid system.

Preparation, characterization and activity evaluation of p–n junction photocatalyst p-NiO/n-ZnO

In this paper, p–n junction photocatalyst NiO/ZnO was prepared by the sol–gel method using Ni (NO3)2 and zinc acetate as the raw materials. The structural and optical properties of the p–n junction photocatalyst NiO/ZnO were characterized by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, UV–Vis diffuse reflection spectrum (DRS) and the fluorescence emission spectra. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic reduction of Cr2O7 2− and photocatalytic oxidation of methyl orange (MO). The results showed that the photocatalytic activity of the p–n junction photocatalyst NiO/ZnO is much higher than that of ZnO on the photocatalytic reduction of Cr2O7 2−. However, the photocatalytic activity of the photocatalyst is much lower than that of ZnO on the photocatalytic oxidation of methyl orange. Namely, the p–n junction photocatalyst NiO/ZnO has higher photocatalytic reduction activity, but lower photocatalytic oxidation activity. The heat treatment condition also influences the photocatalytic activity strongly, and the best preparation condition is about 400 °C for 2 h. Effect of the heat treatment condition on the photocatalytic activity of the photocatalyst was also investigated. The mechanisms of influence on the photocatalytic activity were discussed by the p–n junction principle.

Preparation, characterization and photocatalytic activity of N-containing ZnO powder

N-containing ZnO photocatalyst was prepared by decomposition of zinc nitrate at different heat treatment conditions. The photocatalyst was characterized by DRS, XRD, TG-DTA, XPS, and BET analysis. The results show that the optimum preparation condition for N-containing ZnO is at 350 °C for 3 h, and the sample shows higher photocatalytic activity. The photo-absorption wavelength range of the samples is shifted to long wavelength. Compared with pure ZnO, the samples show higher visible-light photocatalytic activity. However, under UV irradiation, the photocatalytic reduction activity of the N-containing ZnO is higher than that of pure ZnO, and the photocatalytic oxidation activity of the N-containing ZnO is much lower than that of pure ZnO. It is proposed that the change of photocatalytic activity of the sample should be attributed to the nitrogen introduction. The doped nitrogen atoms in a ZnO crystal lattice will probably cause the conductivity conversion of the sample from n-type to p-type.

Preparation, characterization and activity evaluation of p–n junction photocatalyst p-ZnO/n-TiO 2

In this paper, p-type ZnO powder was prepared by decomposition of zinc nitrate at 350 °C for 1 h. p–n junction photocatalyst p-ZnO/TiO 2 was prepared by ball milling of TiO 2 in H 2O solution doped with p-ZnO. The p–n junction photocatalyst p-ZnO/TiO 2 was characterized by UV–vis diffuse reflection spectrum, scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and the fluorescence emission spectra. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic reduction of Cr 2O 7 2− and photocatalytic oxidation of methyl orange (MO). The results showed that the photocatalytic activity of the p–n junction p-ZnO/TiO 2 is much higher than that of TiO 2 on the photocatalytic reduction of Cr 2O 7 2−. However, the photocatalytic activity of the photocatalyst is much lower than that of TiO 2 on the photocatalytic oxidation of methyl orange. Namely, the p–n junction photocatalyst p-ZnO/TiO 2 has higher photocatalytic reduction activity, but lower photocatalytic oxidation activity. When the amounts of doped p-ZnO are 0.0 and 2.0 wt.%, illumination for 20 min, the photoreduction efficiencies are 15.7 and 42.8%, and the photooxidation efficiencies are 68.1 and 26.1%, respectively. Effect of ball milling time on the photocatalytic activity of the photocatalyst was also investigated. The mechanisms of influence on the photocatalytic activity were also discussed by the p–n junction principle.

Electrodeposited p-type Cu 2O as photocatalyst for H 2 evolution from water reduction in the presence of WO 3

Different p-type Cu 2O powders were prepared from electrodeposition and subjected to analysis of their photocatalytic activity in water reduction. The electrodeposited Cu 2O powders were obtained by scraping the deposited films off the substrate. Under illumination the Cu 2O powders alone were not able to catalyze H 2 generation from water reduction. However, these Cu 2O powders exhibited photocatalytic activity in H 2 generation when they were coupled with n-type WO 3 in suspensions. The coupling was made to avoid back reactions of the photo-induced charges. The electrodeposited Cu 2O powders showed higher photocatalytic activity than a commercially available Cu 2O powder. The suspension containing electrodeposited Cu 2O with a strong [1 1 1] orientation gave a larger amount of H 2 evolution than that containing Cu 2O with a [1 1 0] orientation. Appropriate crystalline-texture tuning, as well as charge delocalization promotion, is looked to as the key issue for efficient H 2 generation from water reduction over p-type Cu 2O photocatalysts.

Photocatalytic Hydrogen or Oxygen Evolution from Water over S‐ or N‐Doped TiO2 under Visible Light

S‐ or N‐doping of TiO2 powder having an anatase or rutile phase extended the photocatalytic activity for water oxidation and reduction under UV light and visible light irradiation. For the reduction of water, anatase‐doped TiO2 showed higher level of activity than that of doped TiO2 having a rutile phase using ethanol as an electron donor. Furthermore, the activity level of S‐doped TiO2 for hydrogen evolution was higher than that of N‐doped TiO2 photocatalysts under visible light. Photocatalytic oxidation of water on doped TiO2 having a rutile phase proceeded with fairly high efficiency when Fe3+ ions were used as electron acceptors compared to that on doped TiO2 having an anatase phase. In addition, water splitting under visible light irradiation was achieved by construction of a Z‐scheme photocatalysis system employing the doped TiO2 having anatase and rutile phases for H2 and O2 evolution and the redox couple as an electron relay.

Preparation and activity evaluation of p–n junction photocatalyst NiO/TiO 2

p–n Junction photocatalyst NiO/TiO 2 was prepared by sol–gel method using Ni(NO 3) 2·6H 2O and tetrabutyl titanate [Ti(OC 4H 9) 4] as the raw materials. The p–n junction photocatalyst NiO/TiO 2 was characterized by UV–vis diffuse reflection spectrum, X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the photocatalyst was evaluated by photocatalytic reduction of Cr 2O 7 2− and photocatalytic oxidation of rhodamine B. The results show that, for photocatalytic reduction of Cr 2O 7 2−, the optimum percentage of doped-NiO is 0.5% (mole ratio of Ni/Ti). The photocatalytic activity of the p–n junction NiO/TiO 2 is much higher than that of TiO 2 on the photocatalytic reduction of Cr 2O 7 2−. However, the photocatalytic activity of the p–n junction photocatalyst NiO/TiO 2 is much lower than that of TiO 2 on the photocatalytic oxidation of rhodamine B. Namely, the p–n junction photocatalyst NiO/TiO 2 has higher photocatalytic reduction activity, but lower photocatalytic oxidation activity. Effects of heat treatment on the photocatalytic activity of p–n junction photocatalyst NiO/TiO 2 were investigated. The mechanisms of influence on the photocatalytic activity were also discussed by the p–n junction principle.