Enhancement Of Photocatalytic Performance Research Articles

Constructing Z-Scheme 0D/2D TiO2 Nanoparticles/Bi2O3 Nanosheet Heterojunctions with Enhanced Visible Light Induced Photocatalytic Antibiotics Degradation and Hydrogen Evolution

Photocatalysis has been regarded as a promising technology for degrading organic pollutants in wastewater and producing hydrogen. In this paper, TiO2 nanoparticles (NPs) were synthesized to improve the visible light absorption of TiO2, which were further combined with Bi2O3 nanosheets to synthesize a series of 0D/2D TiO2 NPs/Bi2O3 nanosheet heterojunctions. The visible light induced photocatalytic activities of the as-synthesized TiO2/Bi2O3 heterojunctions were studied. The optimized catalyst TB-3 with 15 wt% of Bi2O3/TiO2 exhibited the best photocatalytic degradation of tetracycline hydrochloride (TC). The degradation rate constant k of TC over TB-3 was approximately eight times and 39 times greater than that of P25 and Bi2O3, respectively. Additionally, TB-3 showed the highest amount of hydrogen evolution, while that of Bi2O3 was almost zero. The enhancement of photocatalytic performances was ascribed to the improved visible light absorption and the Z-scheme charge transfer path of the TiO2/Bi2O3 heterojunctions, which enhanced the separation efficiency and reduced recombination of photogenerated charge carries, as evidenced by UV–Visible diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and electrochemistry measurements. The active species trapping experiments and the electron spin resonance (ESR) results revealed that ·O2− was the main active substance in the photocatalytic degradation. The possible degradation pathway and intermediate products of TC have been proposed. This work provides experimental evidence supporting the construction of Z-scheme heterojunctions to achieve excellent visible light induced photocatalytic activity.

Conductive Polymers‐Confined Metal‐Organic Frameworks with Enhanced Activity for Highly Efficient Photocatalytic CO2 Reduction

AbstractPhotocatalytic CO2 reduction to valuable fuels is highly desirable to alleviate global warming and energy crisis. Herein, a stable aluminum‐porphyrin metal‐organic frameworks (MOFs) named Al−PMOF, with wide spectral response, is selected as platforms for the construction of efficient photocatalyst to convert CO2 into CO. To enhance the activity of pristine Al−PMOF, highly active reaction sites are introduced through metallization of the porphyrin linkers with Cu2+. Furthermore, the polymerization of pyrrole in the channel of MOFs is also performed to improve the electron conductivity and narrow the band gap. The polypyrrole offers the conductive network to transfer the light‐generated electrons and thus enhances the efficient charge separation. The calculated electronic density of states based on the density functional theory (DFT) further prove the electron interaction between the polypyrrole and the MOFs, which benefit the enhancement of photocatalytic performance of Al−PMOF.

Controlled solvothermal synthesis of ZnO nanoparticles using non-destructive Mg-based channel templates for enhanced photocatalytic performance

ZnO nanoparticles (NPs) were synthesized by solvothermal method using novel water soluble magnesium-based coordination polymers (MCPs) with rutile and anatase topologies as non-destructive templates. The strong interaction between ZnO–Mg(INT)2·H2O or ZnO-(Mg(NT)2 interface results in the increase of nucleation points and the decrease of grain sizes, and well-ordered growth of ZnO NPs via channel template effect. Comparing with other samples, S4 synthesized by the Mg(NT)2 template with anatase-type topology possesses the highest charge separation efficiency, largest surface area and pore volume, and exhibits the best photodegradation efficiency and k, which are 87.5%, 0.01752 min−1 (Rhodamine B, RhB) and 61.6%, 0.00776 min−1 (Tetracycline, TC) for 120 min, respectively. The photocatalytic efficiency for RhB over S4 changes slightly after five runs, which exhibits excellent photostability under ultraviolet–visible (UV–Vis) light irradiation. ·O2− and ·OH radical species play the important role in the photocatalytic process. Notably, the addition of MCP templates significantly improves active ·OH of ZnO via interface interaction, which is also favourable for the enhancement of photocatalytic performance of ZnO NPs. Additionally, photodegradation mechanism and pathways, and formation over ZnO were proposed. The work provides a new idea for designing non-destructive and easily-removed channel templates for the synthesis of ZnO NPs.

A Facile Synthesis of BiO(ClBr)0.5−x/2Ix Microsphere Assembly as High‐efficiency Visible‐light Driven Photocatalyst

AbstractUsing a facile refluxing synthesis, a series of BiO(ClBr)0.5−x/2Ix solid solutions was prepared and applied as photocatalysts for the degradation of organic pollutants. The synthesized solid solutions crystallized in microspheres are constructed by nanoplates which transform into nanosheets for increasing iodine ions contents. Furthermore, introducing iodine ions significantly decreased the optical bandgap of the obtained solid solutions. The photocatalytic activity of these samples over the degradation of Rhodamine B indicates the highest performance of the solid‐solution at x=0.2 with a decomposition efficiency of 92.6 % for 120 mins of reaction under the light emission diode (LED) irradiation which is much higher than that of pure sample and BiOCl0.5Br0.5. This enhancement in photocatalytic performance was attributed to the effective separation of photo‐induced electron‐hole pairs.

Surfactant-induced photocatalytic performance enhancement of europium oxide nanoparticles

Recently, rare earth (RE) elements and their oxides have been attracting more and more attention in the field of photocatalytic degradation. Due to the unique 4 f electronic structure and optical properties, the RE element, europium (Eu), together with its oxides, are often used for surface modification of other photocatalysts. Nevertheless, the photocatalytic degradation property of europium oxide has been rarely reported. In this study, we synthesized Eu2O3 nanoparticles via chemical precipitation and calcination processes, and performed surface modification by using surfactants as polyvinyl pyrrolidone (PVP) and hexadecyl trimethyl ammonium bromide (CTAB). Compared with pure Eu2O3 nanoparticles and those synthesized with PVP, photocatalytic degradation efficiencies of Eu2O3 nanoparticles synthesized with surfactant CTAB for degrading rhodamine B dye demonstrated to be improved by 16% and 12%, respectively. The ultraviolet-visible diffuse reflectance spectra measurements indicate that CTAB can increase the bandgap of Eu2O3 due to the reduction of oxygen defects. Photoluminescence spectra demonstrate that the surfactant would affect the luminescence of Eu3+ and carrier redistribution of energy levels.

Enhancement of photocatalytic performance in degradation of aqueous trichloroethylene and methylene blue by using TiO2 thin film fabricated by cellulose nanocrystals templating and Nb doping

Enhancement of photocatalytic performance in degradation of aqueous trichloroethylene and methylene blue by using TiO2 thin film fabricated by cellulose nanocrystals templating and Nb doping

Synthesis of 0D/2D CdSe/HSr2Nb3O10 n–n heterojunction with excellent visible-light-driven photocatalytic performance

In this study, a novel CdSe/HSr2Nb3O10n-n heterojunction was developed through successive hydrothermal reaction of zero-dimensional (0D) CdSe (CE) quantum dots (QDs) anchored on two-dimensional (2D) HSr2Nb3O10 nanosheets (HSNO-ns) with the assistance of microwave heating. The physicochemical properties of CE-QDs/HSNO-ns composites were systematically discussed by XRD, SEM, TEM, DRS, and XPS. The photocatalytic performance of samples was evaluated through photo-degradation of methyl orange (MO). The n-n heterojunctions on the impact of the enhanced photocatalytic activity mechanism was studied through the photocurrent and PL curves. The CE50/HSNO-ns photocatalyst exhibited the highest photo-degradation efficiency, which decomposed MO solution (25 mg·L−1) completely as few as 5 min under the visible light irradiation (λ > 420 nm). Based on the physicochemical and catalytic properties, the enhancement of photocatalytic performance is mainly attributed to the construction of a n-n heterojunction between CE-QDs and HSNO-ns, as well as the increase in the visible-light region.

Enhanced photocatalytic hydrogen evolution and CO2 to CH4 selectivity of Co3O4/Ti3+-TiO2 hollow S-scheme heterojunction via ZIF-67 self-template and Ti3+/Ov

The potential would be an important issue for enhancing photocatalytic HER and CO2 photoreduction selectivity. Herein, the Co3O4/Ti3+-TiO2 hollow S-scheme heterojunction is fabricated via continuous light modification-chemical-annealing-reduction method. Evaluated by photocatalytic performance, the as-prepared Co3O4/Ti3+-TiO2 hollow S-scheme heterojunction exhibits remarkable photocatalytic performance enhancement than single TiO2, including hydrogen evolution (∼396.16 μmol/g·h, ∼15 folds) and CO2 photoreduction (H2/CH4/CO: ∼20.32/80.57/9.85 μmol/g·h, ∼20 folds), and achieves CO2 photoreduction to CH4 selectivity enhancement, which can be mainly ascribed to the synergism of Ti3+/Ov and S-scheme heterojunction. There, Ti3+/Ov can not only increase the solar efficiency, but also decrease the energy barrier of H+ and ∗CO photoreduction to enhance HER and CO2 to CH4 selectivity, including promote the H+ diffusion and CO2 absorption. Additionally, the formed Co3O4/Ti3+-TiO2 S-scheme heterojunction can promote the photo-generated carrier separation/transportation. Also, the hollow 3D structure obtained by ZIF-67 self-template can increase solar efficiency and stability.

CdS-loaded three-dimensional ordered macroporous composite material In2O3-TiO2: Construction of type II heterostructure and enhancement of photocatalytic performance

With the help of polystyrene template, the indium oxide-titanium dioxide (In2O3-TiO2) composite with a three-dimensional ordered macroporous (3DOM) structure was synthesized first, then cadmium sulfide (CdS) was loaded on the surface, and eventually 3DOM CdS/In2O3-TiO2 composites were prepared. 3DOM CdS/In2O3-TiO2 mainly presents the anatase structure of TiO2, while CdS and In2O3 exist in the composite with low crystallinity. Compared with the monomer, the light absorption performance of the composite is significantly improved. The regular and well-organized three-dimensional ordered macroporous structure broadens the absorption of visible light, optimizes the charge transfer efficiency, and extends the photogenerated carrier life. The presence of heterojunctions in 3DOM CdS/In2O3-TiO2 leads to enhanced performance of photodegradation and photolysis of water for hydrogen production. In particular, the hydrogen production of 3DOM CdS/In2O3-TiO2 is 40.7 times that of the commercially available P25. Through the capture experiments, the possible photocatalytic reaction mechanism was speculated.

Multivalent Effect of Defect Engineered Ag2S/g-C3N4 3D Porous Floating Catalyst with Enhanced Contaminant Removal Efficiency.

Chlorophenols, as a major environmental pollutant, enter water systems through industrial wastewater, agricultural runoff and chemical spills, and they are stable, persistent under natural conditions, and highly hazardous to water resources. The objective of this article is to prepare Ag2S-modified C3N4 three-dimensional network photocatalyst by calcination method to use photocatalysis as an efficient, safe, and environmentally friendly method to degrade chlorophenols. Ag2S/C3N4 has an excellent visible light absorption range, low band gap, effective separation of photogenerated charges, and active free radicals production, all of which make for the enhancement of photocatalytic degradation performance of the Ag2S/C3N4 system. Under the light irradiation (λ ≥ 420 nm), the photocatalytic degradation efficiency of 2,4,6-Trichlorophenol reach 95% within 150 min, and the stable photocatalytic degradation activity can still be maintained under different pH water environment and four degradation cycles. When Ag2S is loaded on ACNs, more photogenerated electrons are generated and subsequent reactions produce highly reactive groups such as •O2- and •OH that will originally be able to continuously attack TCP molecules to degrade pollutants. Therefore, this study shows that the photocatalyst provides a novel research approach for realizing the application in the field of pollutant degradation.

Remarkable enhancement of photocatalytic performance in LaCrO3 through a controlled chemical reduction process.

A controlled chemical reduction process was performed on LaCrO3 assisted by CaH2 at a relatively low temperature (773 K), and the impact on the photocatalytic and magnetic properties is discussed. The reduction process leads to the formation of oxygen vacancies that enhance photocatalytic properties by acting as traps that retard the hole/electron recombination processes. In addition, the existence of oxygen defects induces some subtle structural modifications, resulting in Cr-O-Cr angle variation that influences the magnetic behavior of the material. Therefore, the use of a controlled chemical reduction process is an effective method for tunning the physical-chemical properties of transition-metal oxide-based materials, even in cases with high chemical stability.

Surface Character of Magnetic Ce-doped TiO2 for Photocatalytic Performance Enhancement

Using a modified sol-gel method for magnetic photocatalyst, the core shell structure of Ce-doped TiO2@SiO2@ferrite composite nanoparticles (NPs) was created. X-ray diffraction (XRD), Brunauer–Emmit–Teller (BET), and a superconducting quantum interference device (SQUID) were used to examine the physicochemical properties of the products as they were prepared. The ultraviolet-visible spectrometry (UV-vis) was used to measure the catalyst's photocatalytic activity. On the composite NPs' outer shell coating, the anatase phase related to the TiO2 structure was constructed. On the Ce-doped TiO2 layers, a mesoporous structure with uniform pore size was created, resulting in a specific surface area of 111.916 m2g-1. In the meantime, the thin TiO2 coating contained the redox couple of Ce3+ and Ce4+. An external magnetic field can also be used to separate the catalyst's magnetic NPs from the reaction system. In the aqueous solution of methylene blue (MB), the degradation efficiency and product performance were both 50 percentage

G-C3N4-Loaded Carbon Nanofiber for Efficient Photocatalytic Hydrogen Production

g-C3N4-loaded carbon nanofibers (CNCNF) were obtained via electrostatic spinning and high temperature calcination. Highly crystalline g-C3N4 can be obtained at 800 °C due to the protection of carbon nanofibers. Benefiting from the high conductivity of carbon nanofibers and the high carrier separation efficiency of g-C3N4, CNCNF shows a significantly enhanced photocatalytic hydrogen production activity (7.7-fold more than pristine g-C3N4), also, the mechanism of photocatalytic performance enhancement is discussed.

Low bandgap carbon nitride nanoparticles incorporated in titania nanotube arrays by in situ electrophoretic anodization for photocatalytic CO2 reduction

We report an in situ electrophoretic anodization process to realize a binary semiconductor heterojunction photocatalyst comprising green-emitting, water-soluble carbon nitride (CN) nanoparticles (NPs) embedded in TiO2 nanotube (TNT) arrays. Embedding CN inside a TiO2 matrix eliminates the possibility of the CNNPs leaching away during photocatalysis or photoelectrochemistry. The synthesized CN exhibits visible light absorption down to 600 nm and an unusually redshifted green emission peak at 527 nm, which are attributed to a carbon rich g-C3N4 composition with a C:N ratio of ∼ 1.9 at the surface. Spectroscopy revealed the excess carbon to be both amorphous and graphitic while the structural features characteristic of g-C3N4 were preserved. Raman spectroscopy, transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS) analysis verified the formation of the heterostructure as well as indicated strong interaction between the CN and TiO2 in the hybrid. The CNNP@TNT hybrid demonstrated superior performance in sunlight driven photocatalytic CO2 reduction without the need for a sacrificial agent. The CO yield of photoreduction showed a more than threefold improvement for the CNNP@TNT hybrid compared to the stand-alone TNT photocatalyst. The synergistic enhancement of photocatalytic performance emerged due to the formation of a high-quality interface between the constituent semiconductors (TiO2 and CN) that facilitated efficient charge carrier separation. Density functional theory (DFT) calculations showed the feasibility of efficient photogenerated electron-hole pair separation at the heterointerface. Molecular dynamics (MD) simulations validated the facile dispersibility of CNNPs in water and polar solvents.

A Twin S-Scheme Artificial Photosynthetic System with Self-Assembled Heterojunctions Yields Superior Photocatalytic Hydrogen Evolution Rate.

Designing heterojunction photocatalysts imitating natural photosynthetic systems has been a promising approach for photocatalytic hydrogen generation. However, in the traditional Z-Scheme artificial photosynthetic systems, the poor charge separation, and rapid recombination of photogenerated carriers remain a huge bottleneck. To rationally design S-Scheme (i.e., Step scheme) heterojunctions by avoiding the futile charge transport routes is therefore seen as an attractive approach to achieving high hydrogen evolution rates. Herein, a twin S-scheme heterojunction is proposed involving graphitic C3 N4 nanosheets self-assembled with hydrogen-doped rutile TiO2 nanorods and anatase TiO2 nanoparticles. This catalyst shows an excellent photocatalytic hydrogen evolution rate of 62.37mmol g-1 h-1 and high apparent quantum efficiency of 45.9% at 365nm. The significant enhancement of photocatalytic performance is attributed to the efficient charge separation and transfer induced by the unique twin S-scheme structure. The charge transfer route in the twin S-scheme is confirmed by in situ X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) spin-trapping tests. Femtosecond transient absorption (fs-TA) spectroscopy, transient-state surface photovoltage (TPV), and other ex situ characterizations further corroborate the efficient charge transport across the catalyst interface. This work offers a new perspective on constructing artificial photosynthetic systems with S-scheme heterojunctions to enhance photocatalytic performance.

Magnetic Fe3O4/Bi2O2(OH)(NO3) as a sunlight-driven photocatalyst for rhodamine B degradation

A magnetic separable photocatalyst based on Fe3O4/Bi2O2(OH)(NO3) was synthesized using a two-step method based on co-precipitation and a hydrothermal route. The photocatalytic activity of the prepared Fe3O4/Bi2O2(OH)(NO3) for degradation of rhodamine B (RhB) dye under natural sunlight irradiation was investigated. The 3%Fe3O4/Bi2O2(OH)(NO3) photocatalyst, comprising 3 ​mol% of Fe3O4, showed high efficiency (about 98.7%) after 120 ​min of photo illumination. The photogenerated holes played a prominent role in the photodegradation of the dye. The present finding demonstrated the enhancement of photocatalytic performance using the fabrication of a novel, sunlight-active photocatalyst with a low electron-hole recombination rate at the interface.

Environmentally friendly supermolecule self-assembly preparation of S-doped hollow porous tubular g-C3N4 for boosted photocatalytic H2 production

Utilization of graphitic carbon nitride (g–C3N4)–based materials for photocatalytic hydrogen production to alleviate energy problems is a hot topic of research nowadays, thus the design and synthesis of highly efficient g-C3N4 materials remains a significant challenge. Herein, the sulphur-doped hollow porous tubular g-C3N4 (S-HPTCN) was successfully synthesized by a facile environmentally friendly supramolecule self-assembly strategy. Photocatalytic H2 evolution tests show that the as-prepared optimal S-HPTCN achieved a high H2 production of up to 22.04 mmol g−1 h−1 with the turnover frequency (TOF) of 429.7 h−1 and the apparent quantum efficiency (AQE) of as high as 7.8% at wavelength of 420 nm. The enhancement of remarkable photocatalytic H2 performance is mainly attributed to the synergetic effect of morphology and elemental doping. This research provides an effective design idea of developing high-efficient g–C3N4–based material for solar to hydrogen.

The Strengthened Photocatalytic NOx Removal of Composites Bi4O5Br2/BiPO4: The Efficient Regulation of Interface Carriers by Integrating a Wide-Bandgap Ornament

A series of binary composites Bi4O5Br2/BiPO4 (PBX) was fabricated through a simple mechanical ball milling protocol. Relevant microstructural, morphological, and optical properties were thoroughly analyzed via various techniques. The integration of both components was confirmed to produce heterojunction domains at the phase boundaries. Upon exposure to visible light irradiation, the as-achieved PBX series possessed the reinforced photocatalytic NOx removal efficiencies and the weakened generation of toxic intermediate NO2 in comparison to both bare components, chiefly attributed to the efficient transport and separation of carriers and boosted production of superoxide radicals (·O2-) through the combination of a wide-bandgap ornament BiPO4 as an electron acceptor. In particular, the composite PB5 with the optimal phase composition exhibited the highest NOx removal of 40% with the lowest NO2 formation of 40 ppb among all tested candidates. According to the band structures' estimation and reactive species' detection, a reasonable mechanism was ultimately proposed to describe the migration of charge carriers and the enhancement of photocatalytic performance.

Colloidal Cu-doped TiO2 nanocrystals containing oxygen vacancies for highly-efficient photocatalytic degradation of benzene and antibacterial

Development of suitable colloidal photocatalysts with excellent photocatalytic performance under visible light is essential for indoor environmental remediation. In this study, colloidal Cu-doped TiO2 (Cu-TiO2) nanocrystals containing oxygen vacancies (OVs) were synthesized by a facile sol-hydrothermal method and their photocatalytic performances for benzene degradation and antibacterial were investigated. Characterization results revealed that the doping of Cu induced grain size reduction and bandgap narrowing of TiO2 nanocrystals, as well as the formation of abundant OVs in the TiO2 crystal structure, resulting in enhanced light absorption capacity and charge carrier separation efficiency. The optimized colloidal Cu-TiO2 nanocrystals could achieve a maximum degradation rate constant of 0.364 h−1 for the photocatalytic degradation of benzene and a high antibacterial rate of more than 99.99% against both Escherichia coli and Staphylococcus aureus, which were far superior to those of the pristine TiO2. The effects of Cu dopants and OVs on the band structure of TiO2 were revealed by density functional theory (DFT) calculations combined with experimental characterizations, and a possible mechanism for the enhancement of Cu-TiO2 photocatalytic performance was proposed. This work offers a promising method for the synthesis of colloidal TiO2-based nanocrystals with excellent photocatalytic performances for the practical application in indoor environmental remediation.

A Review on Pulsed Laser Preparation of Nanocomposites in Liquids and Their Applications in Photocatalysis

The purpose of photocatalysis is to realize the conversion between solar energy and chemical energy, and it is essential to develop a high-performance photocatalyst under visible-light irradiation. The conventional methods for photocatalyst preparation are mainly wet chemical routes, and abundant yields can be obtained. However, the products are not neat and accompanied by chemical groups and impurities, which are not beneficial for the enhancement of photocatalytic performance. In recent years, as a powerful tool for nanomaterial fabrication, pulsed laser heating in a liquid medium has been utilized to prepare a variety of nanocomposites. Products with synergistic effects and high crystallinity can be rapidly prepared under pulsed laser selective heating, which is beneficial for obtaining more effective photocatalytic performance. In this review, the typical characteristics of pulsed laser heating in liquids and their prepared nanocomposites for photocatalytic applications are summarized. This review not only highlights the innovative works of pulsed-laser-prepared nanocomposites in liquids for photocatalysis but also briefly introduces the specific challenges and prospects of this field.