Photocatalytic Degradation Rate Research Articles

Boosting the photocatalytic activity of bismuth vanadate (BiVO4) via optimization of the internal polarization

Photocatalytic performance can be improved by optimizing the morphology and surface texture of the photocatalyst or forming different p-n and/or n-n heterojunctions. Although the heterojunction system enhances photocatalytic property; however, an internal spontaneous polarization electric field may be much more effective due to the separation of electron-hole pairs when the polarization field forces them to move in different directions. The present study demonstrated this insight where the BiVO4 synthesis condition and polarization field forces were controlled via homogeneous precipitation in the presence of polyvinylpyrrolidone (PVP). The as-synthesized BiVO4 photocatalysts' structure and morphology were investigated using XRD, SEM, Raman, DRS, and PL. The result revealed that the increase of PVP concentration reformed the shaping to the truncated bipyramid-like shape and creates a spontaneous internal polarization that enhanced BiVO4 photocatalytic performance. The photocatalytic activity of BiVO4 was evaluated by monitoring the photocurrent enhancement using chronoamperometry, electrochemical impedance spectra and the photodegrading of methylene blue (MB) aqueous solution to harmless compounds in the presence of light. The spontaneous polarization between the different facets of BiVO4 crystal enhances the e−/h+ separation during internal facets homojunction and leads to four times photocurrent enhancement and the MB photocatalytic degradation rate increased from 0.43 to 1.92 min−1.

The Synthesis of Ag/TiO2 via the DC Magnetron Sputtering Method and Its Application in the Photocatalytic Degradation of Methyl Orange in Na2SO4 Solution

TiO2 and TiO2 films modified with Ag (Ag/TiO2) were prepared via the DC magnetron sputtering method and the degree of modification was controlled via the sputtering power and time of Ag. The microstructures and properties of these films were characterized using field emission scanning electron microscopy, X-ray diffractometry, ultraviolet–visible diffuse reflectance spectrometry, atomic force microscopy, and X-ray photoelectron spectroscopy (XPS). The results show that the prepared films have an anatase structure. Compared with pure TiO2, Ag deposition can improve the utilization of light. The three-dimensional images of Ag/TiO2 clearly show that with the increase in Ag sputtering power and sputtering time, Ag particles on the surface of the film gradually increase, and the structure of the film is relatively dense. The photocatalytic effect of Ag/TiO2 films is the best when the Ag sputtering power is 5 W and the sputtering time is 50 s. Under high-pressure mercury lamp irradiation, the photocatalytic degradation rate of methyl orange (MO) in pure MO solution with Ag/TiO2-5 W-50 s can reach 100% within 55 min, whereas that in MO-Na2SO4 mixed solution can reach 99.55% within 65 min. The results suggest that the presence of Na2SO4 in MO solution can inhibit the degradation of MO using Ag/TiO2, the result of XPS suggests that Na2SO4 accelerates the oxidation of Ag, which may lead to an increase in the recombination rate of photogenerated electron–hole pairs and a decrease in the degradation rate. During the process of recycling photocatalysts, the degradation rate of MO was apparently reduced. A possible reason is that the Ag particles have been oxidized and products of photocatalytic degradation are on the surface of the photocatalyst. The photocatalytic degradation mechanism was studied.

Boosting photocatalytic activity in ternary lamellar hierarchical structured ZnFe2O4/polymeric carbon nitride by constructing an electronic bridge

Photocatalytic technology is one of the ideal approaches for clean energy production and environmental pollution control in the future. However, the rapid recombination of photo-generated charge carriers is a bottleneck problem of low solar energy conversion efficiency. Herein, a magnetic ZnFe2O4/Pt/polymeric carbon nitride (PCN) semiconductor catalyst is designed and prepared for high-performance photocatalytic hydrogen production reaction and photocatalytic degradation rate of RhB. It exhibits 339.31 μmol·g−1·h−1 hydrogen production rate and 96.08 % photocatalytic degradation rate of RhB within 120 min under visible light. The introduction of Pt, constructing an electronic bridge, accelerated the transfer of photo-generated carriers, meanwhile, the smaller band gap of the ternary composites enabled the generation of more photo-generated electrons. The internal electric field accelerated the accumulation of electrons and holes in the conduction band of ZnFe2O4 and valence band of PCN, thus photocatalytic activity is greatly enhanced. The electron-hole separation is also improved and the transport of photo-generated electrons is facilitated by the special structure of the heterojunction and the unique morphology of PCN. In addition, the used catalyst can be recovered through magnetic fields, and this magnetic catalytic system has great application prospects in the fields of photocatalytic hydrogen production and pollutant degradation.

Synthesis, Characterization, and Photocatalytic Activity of Cu-Doped MgO Nanoparticles on Degradation of Methyl Orange (MO)

The purpose of this study is to synthesize Cu-doped MgO nanoparticles and test the performance of photocatalytic degradation of methyl orange (MO). Mg(NO3)2, CuCl2, NaOH, and fresh Calotropis procera leaf extract were used as precursors. The prepared nanoparticles were characterized by using FT-IR, XRD, SEM, and UV-Vis spectrometer to study the functional group, crystal structure, surface morphology, and absorption edge, respectively. The wide band above 3000 cm−1 from the FT-IR spectrum corresponds to the stretching vibrations of flavonoids and phenolic compounds of Calotropis procera leaf extract. Furthermore, the Mg-O bonding of undoped MgO and Cu-doped MgO NPs is represented by new peaks which appeared at 831 and 835 cm−1, respectively. The crystal size of undoped MgO and Cu-doped MgO nanoparticles is 13.04 nm and 12.08 nm, respectively. The SEM microstructure of pure MgO showed higher agglomeration than the Cu-doped MgO nanoparticles. The degradation efficiency of the Cu-doped MgO NPs was compared with that of the MgO NPs, and the photocatalytic activity of these NPs was evaluated using the photocatalytic degradation rates of MO dye. Cu-doped MgO NPs showed higher degradation efficiency than pure MgO NPs. The insertion of Cu in the MgO structure improved the photocatalytic efficiency of the MgO NPs under optimal conditions. Therefore, Cu-doped MgO exhibits high photocatalytic activity compared with undoped MgO nanoparticles under sunlight irradiation.

Fabricated layered g-C3N4 nanosheets for high efficiency photocatalytic degradation of atrazine：Insight into terminal-NHx in-situ activation of H2O2

It is well known that graphite-like carbon nitride (g-C3N4) is a good photocatalyst for in-situ the production of H2O2. However, how to activate H2O2 generating the strong oxidizing ·OH is the key factor to affect the degradation of pollutants. In this paper, the layered g-C3N4 nanosheets were prepared by using urea and H2O with different mass ratios and calcined in Muffle furnace by one-step synthesis method. The morphology, composition and structure of photocatalysts were analyzed, indicating that the as-prepared L-g-C3N4-7 had abundant edge regions in comparison with L-g-C3N4 made by solid urea. The photocatalytic performance of g-C3N4 nanosheets was investigated with atrazine (ATZ) as the target pollutant in water. The results revealed that the prepared L-g-C3N4-7 exhibited the best photocatalytic activity in visible light (λ ≥ 420 nm). The degradation of 1.0 mg/L ATZ reached over 96% after 3 hours and the photocatalytic degradation rate constant (k) was 6.8 times than that of L-g-C3N4 photocatalyst. In addition, under the same conditions, the H2O2 production of L-g-C3N4-7 was 4.5 times than that of L-g-C3N4 photocatalyst. Based on the capture experiments of free radicals, it was found that the contribution rate of ·OH in L-g-C3N4-7 photocatalytic increased to 17 % compared to 4 % of L-g-C3N4 photocatalyst during the degradation of ATZ. The ·OH quantitative experiment indicated that the L-g-C3N4-7 photocatalyst could obviously activate H2O2 to generate ·OH and the amount of ·OH was 2.5 times than that of the L-g-C3N4 photocatalyst. More importantly, a large amount of terminal-NHx (14.6 %) in L-g-C3N4-7 was measured by the XPS, FT-IR and zeta potential. The additive H2O2 adsorption experiment in the dark was used to confirm terminal-NHx sites of L-g-C3N4-7 photocatalyst, which was beneficial to adsorb and activate H2O2. The results illustrated that the L-g-C3N4-7 photocatalyst with rich edge regions and terminal-NHx had the characteristics of in-situ the activation of H2O2 to generate ·OH. The findings suggest that designing and developing efficient g-C3N4 photocatalysts pave a new avenue for activating in situ self-synthesizing H2O2 and the removal of atrazine in water.

Removal and photocatalytic degradation of methylene blue on ZrO2 thin films modified with Anderson-Polioxometalates (Cr3+, Co3+, Cu2+): An experimental and theoretical study

In this work, several ZrO2 thin films modified with Anderson-type polyoxomolybdates (POMs) with general formula (NH4)6-n[XMo6O24H6]-6+n where X = Co3+, Cr3+ and, Cu2+ were prepared. Thin films were characterized through SEM and EDX assay, UV–Vis diffuse reflectance and Fourier Transform Infrared (FTIR) assay. The optical bandgap of ZrO2 thin films was determined to be 3.25 eV, while the modified thin films showed a red shift in the optical activity compared with bare ZrO2 thin films. Methylene Blue (MB) adsorption studies showed that Freundlich isotherm describes properly the experimental data for modified-ZrO2 thin films. Besides, the kinetic results showed the MB adsorption of modified-ZrO2 thin films was superior to bare ZrO2 thin film. The adsorption rate values (K2) of the pseudo-second order model follow these trend ZrO2/CrPOM > ZrO2/CoPOM > ZrO2/CuPOM > ZrO2. The photocatalytic activity of the thin films for MB decomposition under UV and Visible irradiation was studied. Among all the catalysts, the ZrO2 thin films showed the lowest photocatalytic degradation rate kap value (kap = 1.5 × 10−3 min−1), while the best result was obtained for ZrO2/CrPOM thin films (kap = 5.7 × 10−3 min−1) under UV irradiation. Besides, this was the only catalyst efficiently active in MB degradation under visible irradiation, these materials reach 10.4 % after 100 min under visible irradiation. Finally, chemical calculations supported the observed results, by means of TDDFT, EDA analysis, Fukui function and periodic DFT calculations.

Preparation of Novel Layered High Entropy Bismuth-Based Materials and their Photocatalytic Degradation Mechanism.

We prepared BiOCl, BiO(ClBr), BiO(ClBrI), and BiO[ClBrI(CO3)0.5] materials using a simple coprecipitation method. It was found that adjusting the number of anions in the anion layer was conducive to adjusting the band structure of BiOX and could effectively promote the migration and separation of photogenerated carriers, thus improving the photocatalytic activity. We first selected methyl orange (MO) as the study pollutant and compared it with BiOCl, BiO(ClBr), and BiO(ClBrI). The first-order kinetic constants of MO degradation by BiO[ClBrI(CO3)0.5] increased by 90.3, 33.9, and 3.1 times, respectively. The photocatalytic degradation rate of methylene blue by BiO[ClBrI(CO3)0.5] was 89.5%, indicating the excellent photocatalytic performance of BiO[ClBrI(CO3)0.5]. The stability of BiO[ClBrI(CO3)0.5] was demonstrated through cyclic experiments and XRD analysis before and after the reaction. The photocatalytic degradation of MO by BiO[ClBrI(CO3)0.5] showed that h+ and 1O2 were the main active oxidizing species and •O2- was the secondary active substance. Overall, our work provides new ideas for the synthesis and degradation of organic pollutants by using two-dimensional anionic high-entropy materials.

A nano photocatalyst rGO/TiO2 modified by sol–gel‐irradiation and its degradation of deoxynivalenol in liquid products

SummaryThe rGO/TiO2 nanocomposite photocatalyst was synthesised using the sol–gel‐irradiation way to efficiently remove deoxynivalenol (DON) for the grains product's safety and quality. With the nanosize effect of irradiation, the photocatalyst has a smaller average grain size, preventing the recombination of electrons and holes. Moreover, based on UV–Vis DRS study, rGO/TiO2 could utilise visible light and have a broader response range to light. Furthermore, to the application, the photocatalyst rGO/TiO2 with 30 KGy irradiation dosage had an 80.32 ± 4.41% photocatalytic degradation rate of DON. Compared to the photocatalyst without irradiation, there was a 9.98% increase in the degradation rate. This result provided an excellent candidate photocatalyst for the removal of DON and also promoted the development of photocatalysis applications.

On the geometry and material stability of tubular PVDF-TiO2 static mixer membrane contactors for photocatalytic ozonation of micropollutants

The prevention of ozone hotspots in ozonation reactors for wastewater treatment is essential for effective degradation of micropollutants without forming harmful by-products. Membrane contactors can provide a bubble-free ozonation process that is able to decrease by-product formation, e.g., bromate formation in bromide-charged wastewater. Furthermore, the geometry of the reactor influences the distribution of dissolved ozone in a membrane contactor. Turbulence promoters can significantly decrease ozone hotspots and increase ozone mass transfer into wastewater. This work presents a fabrication methodology to produce PVDF-TiO2 helical static mixer membranes using the rotation-in-a-spinneret technology. Static mixer membranes combine the functionality of a membrane contactor and a static mixer in a single component. Furthermore, the PVDF matrix is doped with TiO2 particles as photocatalyst. Thus, we present a membrane-based photocatalytic ozonation process to increase the concentration of hydroxyl radicals for degradation of micropollutants under UV radiation. Static mixer membranes increase the ozone mass transfer coefficient by 70% compared to conventional hollow fiber membranes. Furthermore, the specific photocatalytic degradation rate of methylene blue increases by 50% using static mixer membranes. However, this work also reveals a lack of long-term stability of PVDF-TiO2 membranes in the corrosive environment of photocatalytic ozonation. The molecular weight of PVDF decreases by 11% after use in photocatalytic ozonation resulting in a loss of mechanical stability of the membranes. Similar material concepts are required based on ceramic materials which avoid wetting of the porosity.

The design and preparation of NDI modified MOFs for high efficiency removal of MB and Cr(VI)

The naphthalene tetracarboxdiimide (NDI) modified NH2-UiO-66(Zr) and NH2-MIL-101(Cr) (NDI/UZr and NDI/MCr for short) metal organic frameworks (MOFs) materials with strong covalent bond OC–N–CO were designed and prepared by solvothermal method. The comprehensive physical and chemical properties of the materials were characterized, and the adsorption and photocatalytic properties of the materials were evaluated by using methylene blue (MB) and Cr(VI) in single and mixture system. When the initial concentration of MB was 50 mg·L−1, the photocatalytic degradation rate constant of NDI/MCr(2:1) was 10.3 and 13.8 times higher than that of NH2-MIL-101(Cr) and NDI/UZr(2:1), respectively. Additionally, NDI/MCr(2:1) exhibited 1.6 times higher reaction rate constant than that of NDI/UZr(2:1) for the removal of 10 mg∙L−1 Cr(VI). The enhanced adsorption and photocatalytic ability over NDI/MOFs were attributed to the MOFs larger specific surface area and wider spectral response, and NDI showed high electron affinity, superior charge carrier transport properties. Free radical and electron capture experiments indicated that h+, •O2−, and e− were the main active species in the NDI/MOFs system. Among them h+ and •O2− played an essential role in the removal of MB, while e− and •O2− contributed to the photocatalytic reduction of Cr(VI). The mechanism of the photocatalytic process was discussed in detail.

Fabrication of Ag-decorated La0.9Ag0.1FeO3 for efficient photocatalytic degradation of tetracycline under visible light with the assistance of water oxidation

The photocatalytic conversion of molecular O2 into reactive oxygen species, such as superoxide radicals (·O2-), has become the focus in the oxidative removal of organic pollutants. Nevertheless, the inefficient light absorption, limited adsorption of O2, and the fast recombination rate of photo-induced electron-hole pairs considerably impede the conversion efficiency of the photocatalysts. Herein, we report the synthesis of Ag@LAFO photocatalyst, which contains Ag nanoparticles (NPs)-decorated LAFO (Ag-substituted LaFeO3), to enhance the photodegradation efficiency of tetracycline (TC) with the assistance of water oxidation. Structural and spectroscopic analyses confirmed the successful decoration of Ag NPs on LAFO, which was prepared by substituting 10 % La with Ag. The efficiency of TC photocatalytic degradation rate of Ag@LAFO is 76.25 %, which is 6.1-fold higher than that of pure LFO (12.41 %). The trapping experiment of active radicals verified that ·O2- was crucial in the decomposition of TC molecules and was continuously supplied by the reduction of O2 molecules supported by photocatalytic water oxidation. Moreover, the Ag NPs in Ag@LAFO were found to be crucial for boosting the capture of photo-induced electrons and the activation of adsorbed O2. This study offers a new perspective on the conversion of O2 to ·O2- with the assistance of photocatalytic water oxidation for photocatalytic degradation of organic pollutants.

Simulated solar light-driven degradation of micropollutant in water by biochar-based metal-free catalyst: Regulation strategies for electronic structure and morphology engineering

The biochar/h-BN/g-C3N4 (BNC) composite photocatalyst with a spherical sheet cluster structure, was successfully synthesized. Under simulated solar light irradiation, the photocatalytic degradation rate of reactive red 120 by BNC was 87.94 % within 90 min, corresponding to a 3.57-fold higher kinetic constant than that of g-C3N4. The band structure and electron transfer path in BNC were determined using characterizations and density functional theory (DFT) calculations, confirming a type II heterojunction forming. The attraction of h-BN to h+ by electrostatic interaction and biochar's capacity for both electron transfer and storage were confirmed. Doping of biochar was also found to enhance light absorption and provide O vacancy. The existence of piezoelectric effect assisted the movement of photogenerated carriers to the material surface. In the system, the main active oxidation species were h+ and ·O2–. By calculating optical characteristics, the practical activity of photocatalysts is evaluated. Results indicated that the optimal dosage of BNC was 0.5 g/L in the planar reactor, corresponding to an optical thickness of 2.61 calculated by the six-flux radiation absorption–scattering model (SFM). Biochar doping was found to enhance light absorption. A novel photocatalytic mechanism was proposed for promising matel-free BNC.

Copper doped UiO-66@TiO2 heterojunction for highly efficient photodegradation of odors in broiler houses

Odor pollutants produced by broiler houses can significantly impact the quality of the life of residents and the ecological environment, so it is crucial to explore odor purification technologies. In this study, a defect-rich CuUiO-66@TiO2 photocatalyst was successfully synthesized for the photocatalytic degradation of five typical odors in broiler houses. CuUiO-66 and TiO2 in a 1:3 ratio was the most effective in removing odors, capable of removing 99% of methyl mercaptan, 99% of dimethyl sulfide, 99% of dimethyl disulphide, 86.47% of toluene and 63.09% of ethyl acetate in 60 min. After five cycles degradation, the photocatalyst can remain the crystal structure and keep the photocatalytic degradation rate at 95.2% of methyl mercaptan. Furthermore, the proposed mechanisms for the removal of five odors by CU1T3 have been discussed. Therefore, this study has developed a highly efficient photocatalyst that can effectively eliminate odors emitted from broiler houses. This is a promising solution to address the challenges of odor treatment in the near future.

Carbon-doped Bi2MoO6 nanosheet self-assembled microspheres for photocatalytic degradation of organic dyes

Abstract In this paper, carbon-doped Bi2MoO6 (C-Bi2MoO6) nanosheet self-assembled microspheres were prepared by using the solvothermal-calcination route to improve the photocatalytic activity of Bi2MoO6. The characterization results of x-ray diffractometry, Fourier transform infrared spectrometry, Raman scattering, scanning electron microscopy, transmission electron microscopy, BET specific surface area test, and x-ray photoelectron spectrometry indicated that C replaced the O2− anion in the Bi2MoO6 lattice, thinning the nanosheets, decreasing the size of the microspheres, and increasing the specific surface area of the Bi2MoO6. Ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence, electrochemical impedance spectroscopy, transient photocurrent, and linear sweep voltammetry (LSV) spectroscopy demonstrated that the carbon doping reduced the band gap energy, raised the conduction band, and enhanced the photogenerated electron–hole pairs separation efficiency of Bi2MoO6. Benefiting from these favorable changes, the C-Bi2MoO6 microspheres prepared at a molar ratio of C to Bi of 4 (4C-Bi2MoO6) exhibited the highest photocatalytic activity, and the photocatalytic degradation rate constant of rhodamine B by 4C-Bi2MoO6 microspheres was almost 2.26 times that by pristine Bi2MoO6 under simulated solar light. 4C-Bi2MoO6 microspheres (0.2 g/L) presented excellent photocatalytic performance toward RhB (20 mg/L) at pH value 1 and could remove 98.31% of the RhB within 120 min. In addition, 4C-Bi2MoO6 microspheres also possessed a high photocatalytic activity toward methylene blue and tetracycline. 4C-Bi2MoO6 microspheres assembled from thin nanosheets can be used as effective photocatalysts to degrade toxic organic molecules from wastewater.

Novel ceramic supports for catalyst with hierarchical pore structures fabricated via additive manufacturing-direct ink writing

The use of direct ink writing technology, combined with in-situ grown whiskers, has facilitated the development of 3D-printed ceramic catalyst supports-aluminum borate porous ceramics (ABPCs) with hierarchical pore structures. The optimal slurry consists of 0.2 wt% polycarboxylate, 19 wt% water addition, and 1.2 wt% sodium alginate. The most effective printing parameters are determined to be a 1.0 mm nozzle diameter, 10 mm/s printing speed, 4.0 kPa air pressure, and 0.4 mm layer height. After sintering at 1100 ℃, pure-phase aluminum borate (Al18B4O33) ceramics are achieved, leading to the formation of needle-like aluminum borate whiskers. The aspect ratio of whiskers, flexural strength, BET-specific surface area, and photocatalytic activity of ABPCs increase initially and then decrease with increasing sintering temperature. The ABPCs coated with a titanium oxide layer display a photocatalytic degradation rate of 83.92% for methyl orange solution. These results underscore the immense potential of ABPCs in high-temperature catalyst support applications.

A visible-light-driven dual Z-scheme CeVO4/g-C3N4/LaNiO3 hierarchical nanostructure photocatalyst for effective removal of organic pollutants

The major obstacle to restrict the practical application of photocatalysts is the low separation efficiency of photo-induced charge carriers. To overcome the above problem, a novel ternary CeVO4/g-C3N4/LaNiO3 hierarchical nanostructure photocatalyst with dual Z-scheme heterojunction is designed and fabricated by feat of semiconductor energy levels matching engineering. First, one-dimensional (1D) LaNiO3 nanobelts are fabricated by an electrospinning technique. Second, zero-dimensional (0D) g-C3N4 nanoparticles are fixed on 1D LaNiO3 nanobelts through a direct gas-solid reaction. Finally, 1D CeVO4 needle-like nanorods are fixed on g-C3N4/LaNiO3 hierarchical nanostructures through a hydrothermal method. Following exposure to visible-light irradiation for 180 min, the optimized CeVO4/g-C3N4/LaNiO3 hierarchical nanostructure photocatalyst exhibits the highest photocatalytic degradation rate (87.57%) for tetracycline hydrochloride (TCH). Additionally, under the same conditions, the photocatalyst demonstrates its broad applicability by effectively degrading various organic pollutants, including methylene blue (MB) (60.56%), bisphenol A (BPA) (68.00%), ibuprofen (IBU) (57.56%), cefuroxime sodium (CRO) (77.34%), carbamazepine (CBZ) (59.65%) and ciprofloxacin (CIP) (75.16%). The exceptional photocatalytic performance of the CeVO4/g-C3N4/LaNiO3 hierarchical nanostructure photocatalyst can be attributed to the formation of a dual Z-scheme heterojunction among the 1D CeVO4 needle-like nanorods, 0D g-C3N4 nanoparticles, and 1D LaNiO3 nanobelts. The photocatalyst has a large specific surface area and suitable semiconductor energy band positions, providing the hierarchical nanostructures with numerous surface-active sites, rapid charge transfer ability and small charge recombination rate. The design ideas and preparation method proposed in this work have guiding significance for developing other dual Z-scheme heterojunction photocatalysts.

Sonochemical fabrication of S-scheme Bi2O2CO3/g-C3N4 heterojunction for enhanced photocatalytic destruction of rhodamine B and tetracycline pollutants under natural solar radiations

Photocatalysis is a promising low cost green technology to efficiently mineralize refractory contaminants from wastewater. In this novel research, S-scheme Bi2O2CO3/g-C3N4 heterojunctions containing (0-25) wt % Bi2O2CO3 were sonochemically fabricated for mitigation of hazardous rhodamine B dye and tetracycline antibiotic under sunlight radiations of 900 W power. The physicochemical properties of the solid specimen were explored by photoluminescence [PL], diffuse reflectance spectrum [DRS], X-ray diffraction [XRD], Mapping, high resolution transmission electron microscope [HRTEM], selected area electron diffraction [SAED], N2–adsorption–desorption isotherms and X–ray photoelectron spectroscopy [XPS] techniques. As elucidated by HRTEM analysis, 15 wt% of spherical Bi2O2CO3 nanoparticles of 12 nm size were deposited on g-C3N4 of 40 m2/g surface area at nearly equidistant from each other. The point of zero charge of g-C3N4 sheets was shifted from pHPZC 6.2 to pHPZC 4.8 with incorporation of 15 wt % Bi2O2CO3 revealing the production of negatively charged surface that strongly destructed cationic rhodamine B dye. The rate of photocatalytic degradation of rhodamine B dye for heterojunction containing 15 wt% Bi2O2CO3 was 0.0168 min−1 which is three fold higher than that of pristine g-C3N4 nanosheets. The radical scavengers experimental results revealed that superoxide radicals and positive holes are the main reactive species in the degradation process. The exceptional photocatalytic reactivity emerged from construction of S-scheme heterojunction with auspicious electron-hole pair separation and transportation electron-hole pairs and significant redox power.

Synergy of Nd:YAG Picosecond Pulsed Laser Irradiation and Electrochemical Anodization in the Formation of TiO2 Nanostructures for the Photocatalytic Degradation of Pesticide Carbofuran

This study proposes a simple and controlled method for producing TiO2 with phase junction, oxygen vacancies, and Ti3+ by combining picosecond pulsed laser irradiation and electrochemical anodization. Ti mesh was pretreated by irradiating with a picosecond pulsed laser technique using an Nd:YAG laser (1064 nm) at two fluencies, 15 J/cm2 and 30 J/cm2. The samples were then subjected to electrochemical anodization to form TiO2 nanotube arrays on the previously laser-treated surface. This study will investigate the possibility of forming TiO2 nanotube arrays on a pre-laser-treated Ti substrate and determine their physicochemical and photocatalytic properties. The samples were characterized by FESEM, XRD, Raman, XPS, and UV-Vis DRS. UV-Vis spectroscopy was used to observe the progress of photocatalytic degradation for all samples, and degradation products were determined using GC-MS. With the synergistic effects of phase junction, oxygen vacancies, and Ti3+, the laser-treated TiO2 with 30 J/cm2 showed a higher photocatalytic degradation rate (85.1%) of the pesticide carbofuran compared to non-laser-treated TiO2 (54.8%), remaining stable during successive degradation cycles, which has promising practical applications.

Enhanced hydrogen evolution and tetracycline degradation by a Z-scheme g-C3N4 nanosheets loaded CeO2 photocatalyst under visible light irradiation

In the quest to enhance photocatalytic performance, structural regulation and interface engineering stand out as effective strategies for amplifying active sites and fostering the separation of photogenerated electron-hole pairs. In this study, a pioneering approach was employed, utilizing a straightforward two-step calcination method to prepare a novel photocatalyst: porous graphite carbon nitride (g-C3N4, CN) nanosheets (NS) loaded with mesoporous cerium oxide (CeO2/CNNS). The distinctive architecture of CeO2/CNNS not only elevates the specific surface area and catalytic active sites but also facilitates efficient mass transfer. Experimental results and density functional theory (DFT) calculations corroborate the existence of an internal electric field (IEF) within the Z-scheme heterojunction formed by uniformly dispersed CeO2 and CNNS. This IEF proves pivotal in promoting charge separation and migration, thereby maintaining robust redox capabilities. Under visible light irradiation, CeO2/CNNS demonstrates an impressive 4.2-fold increase in the hydrogen production rate compared to bulk g-C3N4 (BCN), coupled with a 48.5% boost in the photocatalytic degradation rate constant (k) of tetracycline (TC). This study not only unveils the innovative design of CeO2/CNNS but also paves the way for a fresh perspective on the design and preparation of multifunctional photocatalysts.

Synthesis of Novel MOF‐Based BixTiy‐BTC and Bi1Ti3‐BTC/Fe3O4 Photocatalysts and Their Application in the Degradation of UDMH in Wastewater

AbstractRemoval of organic pollutants from wastewater remains a significant challenge. Hence, we report a series of novel MOFs based BixTiy‐BTC photocatalysts synthesized by hydrothermal method for decontamination of 1,1‐Dimethylhydrazine (UDMH). The preparation parameters of MOFs were optimized, the best catalytic performance was achieved by adjusting the Bi/Ti molar ratio to 1 : 3, with Bi1Ti3‐BTC a photocurrent density of 0.35 mA/cm2 was reached. The morphology and composition of the materials were analyzed, titanium doping increased the specific surface area. Bi1Ti3‐BTC was loaded with magnetic nano‐Fe3O4, which prevented agglomeration of Bi1Ti3‐BTC and increased the specific surface area, thus improving photocatalytic activity. The band gap structure of the semiconductor materials was estimated by UV‐Vis and XPS valence band spectra, while the separation efficiency of photogenerated carriers was investigated by photocurrent density and PL (Photoluminescence) spectrum. The photocatalytic degradation rate of UDMH rapidly decreased after addition of EDTA, indicating that h+ was the main active species in the photocatalytic degradation process. The photocatalytic removal efficiency of UDMH with Bi1Ti3‐BTC/Fe3O4 at a concentration of 0.5 g/L reached 97.58 % after illumination for 180 min, and after 210 min near quantitative degradation was observed.