Pilot-Scale Studies of WO3/S-Doped g-C3N4 Heterojunction toward Photocatalytic NOx Removal

Due to the rising concentration of toxic nitrogen oxides (NOx) in the air, effective methods of NOx removal have been extensively studied recently. In the present study, the first developed WO3/S-doped g-C3N4 nanocomposite was synthesized using a facile method to remove NOx in air efficiently. The photocatalytic tests performed in a newly designed continuous-flow photoreactor with an LED array and online monitored NO2 and NO system allowed the investigation of photocatalyst layers at the pilot scale. The WO3/S-doped-g-C3N4 nanocomposite, as well as single components, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller surface area analysis (BET), X-ray fluorescence spectroscopy (XRF), X-ray photoemission spectroscopy method (XPS), UV–vis diffuse reflectance spectroscopy (DR/UV–vis), and photoluminescence spectroscopy with charge carriers’ lifetime measurements. All materials exhibited high efficiency in photocatalytic NO2 conversion, and 100% was reached in less than 5 min of illumination under simulated solar light. The effect of process parameters in the experimental setup together with WO3/S-doped g-C3N4 photocatalysts was studied in detail. Finally, the stability of the composite was tested in five subsequent cycles of photocatalytic degradation. The WO3/S-doped g-C3N4 was stable in time and did not undergo deactivation due to the blocking of active sites on the photocatalyst’s surface.

Single-atom Cu anchored catalysts for photocatalytic renewable H2 production with a quantum efficiency of 56%

Single-atom catalysts anchoring offers a desirable pathway for efficiency maximization and cost-saving for photocatalytic hydrogen evolution. However, the single-atoms loading amount is always within 0.5% in most of the reported due to the agglomeration at higher loading concentrations. In this work, the highly dispersed and large loading amount (>1 wt%) of copper single-atoms were achieved on TiO2, exhibiting the H2 evolution rate of 101.7 mmol g−1 h−1 under simulated solar light irradiation, which is higher than other photocatalysts reported, in addition to the excellent stability as proved after storing 380 days. More importantly, it exhibits an apparent quantum efficiency of 56% at 365 nm, a significant breakthrough in this field. The highly dispersed and large amount of Cu single-atoms incorporation on TiO2 enables the efficient electron transfer via Cu2+-Cu+ process. The present approach paves the way to design advanced materials for remarkable photocatalytic activity and durability.

Photocatalytic removal of benzene over Ti3C2Tx MXene and TiO2–MXene composite materials under solar and NIR irradiation

The TiO2/MXene composites prepared by different routes were assessed towards the degradation of organic pollutants under simulated solar light. A notable photocatalytic activity of bare MXene under near infra-red light was discovered.

One-step route for Z-scheme Al2(WO4)3/Bi2WO6 heterojunction toward superior photoelectric and photocatalytic performance

Herein, Al2(WO[Formula: see text]/Bi2WO6 heterojunctions with [Formula: see text]-type structure were successfully prepared by a one-step hydrothermal method. Moreover, the effects of different composite ratios on the properties of materials were explored. The electrochemical tests and photocatalytic degradation experiments showed that the corresponding Al2(WO[Formula: see text]/Bi2WO6 heterojunctions all exhibited improved electrochemical performance and photocatalytic performance than that of the bare Bi2WO6 material. Especially, when the molar ratio of Al to Bi was 2:1, the obtained Al2(WO[Formula: see text]/Bi2WO6 heterojunction displayed the optimal photoelectric and photocatalytic performance. In detail, it depicted the highest photocurrent density, the smallest resistance and the fastest charge transfer rate. What’s more, the RhB solution (10 ppm) could be completely degraded in 30 min under visible-light irradiation, and the removal rate was almost 1.6 times than that of pure Bi2WO6 nanosheets. In the same condition, it also exhibited excellent photocatalytic performance for the degradation of tetracycline (TC) solution (10 ppm) and the K2Cr2O7 solution (40 ppm). These results fully manifested that the constructed Al2(WO[Formula: see text]/Bi2WO6 heterojunction possessed superior photoelectric conversion capacity and outstanding photocatalytic performance. Moreover, based on the obtained experimental results, a [Formula: see text]-scheme mechanism of catalytic degradation of RhB and TC under simulated solar light was proposed and discussed.

Effect of Calcination Conditions on the Properties and Photoactivity of TiO2 Modified with Biuret

A simple wet impregnation-calcination method was used to obtain a series of novel non-metal doped TiO2 photocatalysts. Biuret was applied as C and N source, while raw titanium dioxide derived from sulfate technology process was used as TiO2 and S source. The influence of the modification with biuret and the effect of the atmosphere (air or argon) and temperature (500–800 °C) of calcination on the physicochemical properties and photocatalytic activity of the photocatalysts towards ketoprofen decomposition under simulated solar light was investigated. Moreover, selected photocatalysts were applied for ketoprofen photodecomposition under visible and UV irradiation. Crucial features affecting the photocatalytic activity were the anatase to rutile phase ratio, anatase crystallites size and non-metals content. The obtained photocatalysts revealed improved activity in the photocatalytic ketoprofen decomposition compared to the crude TiO2. The best photoactivity under all irradiation types exhibited the photocatalyst calcined in the air atmosphere at 600 °C, composed of 96.4% of anatase with 23 nm crystallites, and containing 0.11 wt% of C, 0.05 wt% of N and 0.77 wt% of S.

Facile Liquid-Phase Synthesis of a High-Performance Cd-Doped ZnO-Quantum-Dot-Based Photocatalyst

Doping is an effective functional modification method for improving the optical, electrical, and magnetic properties of semiconductors. Here, Cd-doped wurtzite ZnO-quantum-dot (ZQ) zero-dimensional nanomaterials were successfully prepared via liquid-phase synthesis. The experimental results showed that Cd doping can effectively shorten the bandgap, where the optical bandgap range of Cd-doping photocatalysts were 3.31-3.36 eV; in particular, the Cd5-ZQ (Cd contents of 0.5 wt%) sample reduced the bandgap from 3.39 to 3.31 eV compared to that of pure ZQ . This is consistent with the experimental results, where the simulation calculation results indicated the bandgap reduced from 3.107 to 2.912 eV after introducing Cd. Photoluminescence spectroscopy results confirmed the Cd-ion dopants efficiently capture excited electrons and further prolongs the charge lifetime. The degradation of a methylene blue solution under simulated solar light irradiation revealed that the photocatalytic properties of Cd-ZQ nanomaterial with suitable dopant concentration (Cd content 0.5 wt%) was significantly better than those of pure ZQ. The underlying mechanism involves a synergistic effect, and a reasonable and convenient strategy for uprated performance is presented.

g-C3N4/MoS2 Heterojunction for Photocatalytic Removal of Phenol and Cr(VI)

In this study, molybdenum disulfide (MoS2) decorated on graphitic carbon nitride (g-C3N4) heterostructure catalysts at various weight ratios (0.5%, 1%, 3%, 10%, w/w) were successfully prepared via a two-step hydrothermal synthesis preparation method. The properties of the synthesized materials were studied by X-ray diffraction (XRD), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FT-IR), UV–Vis diffuse reflection spectroscopy (DRS), scanning electron microscopy (SEM) and N2 porosimetry. MoS2 was successfully loaded on the g-C3N4 forming heterojunction composite materials. N2 porosimetry results showed mesoporous materials, with surface areas up to 93.7 m2g−1, while determined band gaps ranging between 1.31 and 2.66 eV showed absorption over a wide band of solar light. The photocatalytic performance was evaluated towards phenol oxidation and of Cr (VI) reduction in single and binary systems under simulated sunlight irradiation. The optimum mass loading ratio of MoS2 in g-C3N4 was 1%, showing higher photocatalytic activity under simulated solar light in comparison with bare g-C3N4 and MoS2 for both oxidation and reduction processes. Based on scavenging experiments a type-II photocatalytic mechanism is proposed. Finally, the catalysts presented satisfactory stability (7.8% loss) within three catalytic cycles. Such composite materials can receive further applications as well as energy conversion.