Efficient Visible-light Photocatalytic Activity Research Articles

Revealing the lattice engineering of Delafossite in core–shell CuRhO2@CuGaO2 heterostructure for efficient visible light photocatalytic activity

The establishment of heterojunctions at phase interfaces represents a pivotal strategy for enhancing photocatalytic performance. However, the inferior interfacial contact caused by the mismatch of crystal structure or lattice parameters seriously hampers the rapid and smooth migration of charge carriers in traditional heterojunctions. In this work, a tightly integrated Delafossite-based core–shell CuRhO2@CuGaO2 heterojunction was judiciously designed and constructed via a hydrothermal approach. Experimental and density-functional theory calculation results co-unravel that the built-in electric field is established in the lattice-matched heterogeneous interfaces, thereby providing smooth interface charge separation and transfer via the Z-scheme pathways. Benefitting from the heterojunction effect and unique core–shell coupling architecture, the strong visible light absorption and fast spatial charge transfer are realized in the CuRhO2@CuGaO2 heterostructure. The photocurrent density of the CuRhO2@CuGaO2 heterojunction is nearly 1.25 and 3.75 times those of pristine CuRhO2 and CuGaO2, respectively. As a result, the CuRhO2@CuGaO2 heterostructure reveals an excellent photocatalytic degradation rate of tetracycline hydrochloride, achieving a 3.02 and 2.38-fold improvement than those of the CuRhO2 and CuGaO2, respectively. This work is expected to pave the way for novel insights into the design of efficient heterojunction photocatalysts to steer the rapid photocarrier flows across the heterointerface.

Photostable selenium-assisted ZnS nanocomposite with efficient visible light photocatalytic activity

Selenium-assisted ZnS nanocomposite has been successfully prepared through a simple soft chemical route and their photocatalytic activity was also investigated for degradation of methylene and rhodamine B dye under ultraviolet and sunlight irradiation. Various surface analysis techniques such as XRD, SEM, TEM, UV-visible, XPS, and photoluminescence were used to analyze the formation of Se/ZnS nanocomposites. XRD studies confirmed the formation of the selenium phase along with ZnS and zinc methacrylate. SEM images showed that ZnS and Se nanoparticles self-aggregated to form three-dimensional spherical nano-assemblies of an average size of about 527 nm. The presence of a different type of defect in Se/ZnS was analyzed from PL spectra. The photocatalytic study revealed the complete degradation of methylene blue in 75 min with a rate constant of 0.073 min−1 under UV light irradiation. In contrast, rhodamine B (RhB) degraded in 90 min with a corresponding rate constant of 0.038 min−1 under the same time duration. Further, this nanocomposite was also efficient under natural sunlight, and almost 85% degradation was achieved after 180 min. Thus, the synergistic effect of strong absorption under UV and visible light source of Se/ZnS nanocomposite minimizes the photogenerated electron-hole pair recombination., which makes them excellent photocatalysts towards the degradation of dyes. Also, this nanocomposite reduced the photo-corrosion under light irradiation and improved photocatalytic stability. In addition, scavenger studies and electron spin resonance in combination with spin trapping technique were used to analyze the contribution of reactive species involved in photocatalysis process.

Controllable Synthesis, Photocatalytic Property, and Mechanism of a Novel POM-Based Direct Z-Scheme Nano-Heterojunction α-Fe2O3/P2Mo18.

In order to improve photocatalytic activity and maximize solar energy use, a new composite material Fe2O3/P2Mo18 was prepared by combining polyoxometalates (P2Mo18) with Fe2O3 nanosheets. FT-IR, XRD, XPS, SEM, TEM, UV-vis, EIS, and PL were used to characterize the composite material, and nano-Fe2O3 of different sizes and morphologies with a controllable absorption range was prepared by adjusting the reaction time, and, when combined with P2Mo18, a composite photocatalyst with efficient visible light response and photocatalytic activity was constructed. The EIS, Bode, and PL spectra analysis results show that the Fe2O3/P2Mo18 composite material has outstanding interfacial charge transfer efficiency and potential photocatalytic application possibilities. Model reactions of methylene blue (MB) and Cr (VI) photodegradation were used to evaluate the redox activity of Fe2O3/P2Mo18 composites under simulated visible light. The photocatalytic degradation rate was as high as 98.98% for MB and 96.86% for Cr (VI) when the composite ratio was Fe2O3/P2Mo18-5%. This research opens up a new avenue for the development of high-performance photocatalysts.

Visible light photo-Fenton catalytic properties of starch functionalized α-FeOOH/β-FeOOH/Cu2O p-n-p heterojunction nanostructures

Photocatalysts with p-n-p heterojunctions can result in efficient charge separation. This idea motivated the synthesis of starch functionalized α-FeOOH/β-FeOOH/Cu2O heterojunction nanocomposites. All components in the composite have visible range band gaps. In a step-wise procedure, Cu2O nanostructures were precipitated on starch functionalized α-FeOOH/β-FeOOH nanocomposites. Mott Schottky plots confirmed p-n-p heterojunction formation. It enhanced charge separation and slowed down recombination resulting in efficient visible-light photocatalytic activity. The activity of this photocatalyst was evaluated for the photo-Fenton degradation of p-nitrophenol (PNP) and methyl orange (MO). Both degradation reactions follow zero-order kinetics. The photocatalyst remained stable during the organic pollutant degradation process even after repeated use.

Synthesis of CdS QDs/BaSnO3 nanocomposites via electrostatic self-assembly for visible light photocatalytic deep oxidation of NO

A BaSnO3 sample loaded with CdS quantum dots (CdS QDs/BaSnO3) was prepared by an electrostatic self-assembly method. The obtained CdS QDs/BaSnO3 nanocomposites exhibited an efficient visible light utilization and photocatalytic NO oxidation activity. The experimental results revealed that the loading of CdS QDs tremendously improved the light absorption range and the separation efficiency of photogenerated electron-hole pairs. In-situ DRIFTS tests demonstrated that the introduced Cd2+ could provide new active sites for NO adsorption and activation. Simultaneously, the EPR test showed that the introduction of CdS QDs induced the generation of ·O2–, which was conducive to promoting the deep oxidation of NO. This study provides a facile and effective synthesis method and strategy for improving the photocatalytic NO removal efficiency while significantly suppressing the NO2 concentration.

Novel La3+/Sm3+ co-doped Bi5O7I with efficient visible-light photocatalytic activity for advanced treatment of wastewater: Internal mechanism, TC degradation pathway, and toxicity analysis

Controlling semiconductor photocatalysts by doping rare-earth ions is an effective strategy to improve photocatalytic performance. Simple solvothermal and calcination methods were used to prepare La3+ and Sm3+ modified Bi5O7I nanomaterials. Some characterizations such as XRD, XPS, SEM, TEM, UV–vis, etc. were carried out to explore its structural composition and photoelectrochemical properties. The photocatalytic activity was investigated by simulating the degradation of TC and RhB under visible-light irradiation. The degradation results showed that the photocatalytic efficiency of 4S4L-Bi5O7I was the best among the samples with the 100% degradation rate of TC (Tetracycline hydrochloride) and 93% of RhB (Rhodamine B). The capture experiment and ESR test proved that the active substances that play a role in the photocatalytic degradation of pollutants were ·O2−, 1O2 and h+, and on this basis, the possible degradation mechanism was proposed. The final results showed that La/Sm co-doping expanded the light absorption range of Bi5O7I and improved the charge separation efficiency and the specific surface area. Besides, the surface defects were formed on the surface of Bi5O7I due to ion-doping, which could catch e− to promote the separation and transfer of carriers and improve the photocatalytic activity. LC-MS was used to analyze the possible degradation pathways of TC. And the toxicity of TC was also analyzed via T.E.S.T and Toxtree. The results showed comprehensive toxicity of TC was decreased by 4S4L-Bi5O7I so that the overall water pollution was reduced. This work can provide a reference for the subsequent development of bismuth-based photocatalysts.

Carbonitrides-modified silver phosphotungstate photocatalysts constructed by thermal post-treatment of self-assembled polyoxometalate hybrids for efficient visible-light photocatalytic activity

Carbonitrides-modified silver phosphotungstate (CN-AgPW) photocatalysts were synthesized by self-assembly and solid-phase thermal polymerization. The microstructural and optical properties of the synthesized photocatalysts were systematically investigated, and the photocatalytic activity was evaluated by the degradation of Aflatoxin B1 (AFB1) under visible light (λ ≥ 420 nm) irradiation. The synthesis process, the interaction of compounds, and Z-scheme charge transfer path of the synthesized photocatalysts were investigated. The rate constants k of CN-AgPW-5 are 12.95 and 12.50 times higher than those of CN-390 and AgPW-390, respectively. This study provides a new strategy for the synthesis and enhancement of photocatalytic efficiency of insoluble polyoxometalate photocatalysts.

Two-dimensional photocatalyst with highly efficient and stable visible light photocatalytic activity

Hex ammonium molybdate (AHM), ammonium nitrate (NH4NO3), and glycine were used as the precursors in a microwave-assisted solution combustion synthesis (WSCS) process to create foam-like MoO2 nanoparticles. Methodically investigated was the effect of the glycine/NH4NO3 ratio (=0.25, 0.50, 0.75, 1.0 and 1.25) on the finished goods. The findings indicate that the final morphologies and phases of the products are virtually influenced by the value of Φ. MoO2 nanoparticles measuring 20 to 30 nm can be successfully composited under the condition of Φ=0.50 to produce a foam-like result. The photocatalytic activity of foam-like MoO2 nanoparticles was tested with several pollutants. The results show that foam-like MoO2 nanoparticles have good degradability and stability. The photocatalytic mechanism and fabrication mechanism of foam-like MoO2 has been presented in detail. Using foam-like MoO2-based photocatalyst materials for energy transfer and environment protection is supported by this research.

Two-dimensional photocatalyst with highly efficient and stable visible light photocatalytic activity

Hex ammonium molybdate (AHM), ammonium nitrate (NH4NO3), and glycine were used as the precursors in a microwave-assisted solution combustion synthesis (WSCS) process to create foam-like MoO2 nanoparticles. Methodically investigated was the effect of the glycine/NH4NO3 ratio (=0.25, 0.50, 0.75, 1.0 and 1.25) on the finished goods. The findings indicate that the final morphologies and phases of the products are virtually influenced by the value of Φ. MoO2 nanoparticles measuring 20 to 30 nm can be successfully composited under the condition of Φ=0.50 to produce a foam-like result. The photocatalytic activity of foam-like MoO2 nanoparticles was tested with several pollutants. The results show that foam-like MoO2 nanoparticles have good degradability and stability. The photocatalytic mechanism and fabrication mechanism of foam-like MoO2 has been presented in detail. Using foam-like MoO2-based photocatalyst materials for energy transfer and environment protection is supported by this research.

Facile synthesis of g-C3N4/Ag2C2O4 heterojunction composite membrane with efficient visible light photocatalytic activity for water disinfection

Water pollution, deriving from the contamination of pathogenic bacteria, has posed a threat to human's survival and development. Photocatalytic disinfection is being widely studied in decentralized drink water safety, as traditional disinfection technologies are limited by harmful disinfection by-product and excessive energy consumption. Herein, a novel composite membrane (PN/Ag) with plasmonic heterojunction was synthesized for the efficient photocatalytic disinfection through the combination of polyacrylonitrile (PAN), N-doped carbon dots (NCDs)/g-C3N4 and Ag2C2O4 by electrospinning technique and successive ionic layer adsorption and reaction (SILAR) process. The surface plasmon resonance (SPR) effect of Ag nanoparticles and Schottky barrier formation between metal and semiconductor contributed to the efficient separation of electron-hole pairs and the generation of reactive species, resulting in outstanding photocatalytic disinfection of PN/Ag composite membranes (7.48 and 7.70 log inactivation of E. coli and S. aureus respectively in 80 min) and good reusability under visible light illumination. Moreover, the potential Z-scheme photocatalytic mechanisms were proposed for PN/Ag system according to the band structure and reactive species analysis. The as-proposed PN/Ag composite membranes may shed light on the design and application of materials in water purification.

One-pot microwave synthesis of Pd modified titanium dioxide nanocrystals for 3D aerogel monoliths with efficient visible-light photocatalytic activity in a heated gas flow reactor

We present a one-pot microwave synthesis of Pd modified titanium dioxide nanocrystals for macroscopic aerogel monoliths, which are efficient visible-light photocatalysts for methanol oxidation in a heated gas flow reactor.

Enhancing interfacial charge transfer in mesoporous MoS2/CdS nanojunction architectures for highly efficient visible-light photocatalytic water splitting

Mesoporous MoS2-modified CdS nanojunction networks possessing advantageous electronic connectivity and charge transfer behavior at the interfaces deliver highly efficient visible-light photocatalytic H2 production activity from water splitting.

Carbonitrides-Modified Silver Phosphotungstate Photocatalysts Constructed by Thermal Post-Treatment of Self-Assembled Polyoxometalate Hybrids for Efficient Visible-Light Photocatalytic Activity

Carbonitrides-Modified Silver Phosphotungstate Photocatalysts Constructed by Thermal Post-Treatment of Self-Assembled Polyoxometalate Hybrids for Efficient Visible-Light Photocatalytic Activity

In Situ One-Pot Synthesis of C-Decorated and Cl-Doped Sea-Urchin-like Rutile Titanium Dioxide with Highly Efficient Visible-Light Photocatalytic Activity

Titanium dioxide (TiO2) that offers high light-harvesting capacity and efficient charge separation holds great promise in photocatalysis. In this work, an in situ one-pot hydrothermal synthesis was explored to prepare a C-decorated and Cl-doped sea-urchin-like rutile TiO2 (Cl-TiO2/C). The growth of sea-urchin-like 3D hierarchical nanostructures was governed by a mechanism of nucleation and nuclei growth-dissolution-recrystallization growth from time-dependent morphology evolution. The crystal morphology and the content of Cl and C could be controlled by the volume ratio of HCl to TBOT. Systematic studies indicated that the 0.4Cl-TiO2/C sample (the volume ratio of HCl to TBOT was 0.4) exhibited the highest visible-light photocatalytic activity for the degradation of rhodamine B, with kinetic rate constant (k) of 0.0221 min-1, being 6.5 and 3.75 times higher than that of TiO2 and Cl-TiO2. The enhanced photocatalytic performance could be attributed to the high charge separation and transfer efficiency induced by Cl-doping and C decoration and the excellent light-harvesting capacity caused by its sea-urchin-like nanostructure. Moreover, the 0.4Cl-TiO2/C sample exhibited good reusability and excellent structural stability for five cycles. This facile one-pot approach provides new insight for the preparation of a TiO2-based photocatalyst with excellent photocatalytic performance for potential application in practical wastewater treatment.

Supramolecular Self-Assembly of Nitrogen-Deficient Ag/g-C3N4 Nanofiber Films with Enhanced Charge Transfer Dynamics for Efficient Visible-Light Photocatalytic Activity.

Molecular self-assembly of organic molecules through noncovalent interactions is a powerful strategy for designing functional materials. Herein, we fabricated a novel free-standing Ag/g-C3N4 nanofiber (Ag/CNNF) film via a water-based molecular engineering approach followed by pyrolysis using a cyanuric acid-melamine complex as the precursor. Uniform dispersion of plasmonic Ag nanoparticles and incorporation of nitrogen vacancies were synchronously introduced into the 3D highly interconnected porous CNNF framework. The resulting Ag/CNNF film with multilevel interlayer spacing distributions significantly expedited more sufficient charge transfer dynamics not only at Schottky junction sites but also throughout hierarchical CN by exciton dissociation. Benefiting from the synergistic enhancement in visible light harvesting capability and steered charge carrier transfer in a longitudinal direction, the Ag/CNNF film presented remarkably boosted photocatalytic ability both for hydrogen production and tetracycline degradation. The optimal Ag/CNNF-2 film exhibited a prominent photocatalytic hydrogen evolution rate of 1240 μmol g-1 h-1 without the Pt co-catalyst under visible light illumination, which was 10.3 times as high as that of bulk g-C3N4. Significantly, 1D Ag/g-C3N4 nanofibers self-assembled into an ordered and macroscopic film, which was more favorable in practical applications owing to good reusability and high processability. This work paved the way for the facile preparation of supramolecular self-assembled CN-based film photocatalysts.

Table tennis bat poplar baseplate-derived bismuth molybdate with efficient visible-light photocatalytic activity

Wood waste from sports equipment is regarded as potentially valuable resource, providing attractive material platform to develop efficient photocatalysts. In this study, new bismuth molybdate photocatalyst, P-Bi2MoO6 with wood powder morphology, was prepared using waste table tennis bat poplar baseplates via a facile one-step synthesis using wood bionic processing technique combined with solvothermal method. Photocatalytic activity of samples was evaluated by the decomposition of tetracycline hydrochloride (TC) under visible-light irradiation. Results show that compared with conventional bismuth molybdate, synthesized P-Bi2MoO6 exhibited higher photodegradation efficiency. This can be mainly attributed to the decrease in crystallite size, enrichment in surface-active oxygen species, improved light absorption, efficient carrier separation, and strengthened charge transfer. Electron spin resonance and quenching experiments confirm that OH• and •O2− radicals are the major reactive species during the photocatalytic reaction. This study provides a new synthetic strategy for photocatalysts with different shapes for the purification of water environment.

Boosting of photocatalytic hydrogen evolution via chlorine doping of polymeric carbon nitride.

Chlorine is found to be a suitable element for the modification of polymeric carbon nitride properties towards an efficient visible-light photocatalytic activity. In this study, chlorine-doped polymeric carbon nitride (Cl-PCN) has been examined as a photocatalyst in the hydrogen evolution reaction. The following aspects were found to enhance the photocatalytic efficiency of Cl-PCN: (i) unique location of Cl atoms at the interlayers of PCN instead of on its π-conjugated planes, (ii) slight bandgap narrowing, (iii) lower recombination rate of the electron–hole pairs, (iv) improved photogenerated charge transport and separation, and (v) higher reducing ability of the photogenerated electrons. The above factors affected the 4.4-fold enhancement of the photocatalytic efficiency in hydrogen evolution in comparison to the pristine catalyst.

Facile hydrothermal preparation of a ZnFe2O4/TiO2 heterojunction for NOx removal

Titanium dioxide (TiO2) has become the most promising photocatalyst. It is non-toxic and has a wide range of sources, but its application is limited due to its weak visible light absorption capacity. Compounding with other materials to form heterojunctions has proven to be effective strategies for enabling high photocatalytic performances under visible light. Here, the ZnFe2O4/TiO2 composites had been synthesized by a facile hydrothermal method to realize efficient visible light photocatalytic activity of NOx removal. A series of characterizations, such as XRD, ESR, in-situ DRIFTS, etc., were used to analyze the physical and chemical properties of the photocatalyst, which demonstrated that the composite material had more active sites and a faster electron transfer rate. The optimal sample (12 wt% ZnFe2O4/TiO2) had a NOx removal rate of 54 % nearly 11 times higher than that of original TiO2. On the basis of the above photocatalytic experimental results and characterizations, a possible mechanism or pathway was proposed and illustrated. This work can provide a feasible strategy to prepare TiO2-based composite materials with magnetic separation properties to effectively remove NOx.

Interface engineered efficient visible light photocatalytic activity of MWCNTs/Co doped ZnO nanocomposites: Morphological, optical, electrical and magnetic properties

Active photocatalysts composed of multi-walled carbon nanotubes (MWCNTs)/cobalt-doped zinc oxide nanocomposites were synthesized by a modified sol-gel method. Structural and morphological characterization revealed the formation of ZnO hexagonal wurtzite with cabbage-like structure. TEM and SEM images demonstrate the good surface-surface contact between the MWCNTs and ZnO particles with homogenous distribution of MWCNTs in the powders. The experimental Kubelka–Munk calculations showed that the incorporation of Co markedly reduces the band gap of ZnO, suggesting a promising photocatalytic activity under visible light. Co doping induced a reduction in the dielectric constant values assigned to the substitution of polarized Zn2+ ions by the less polarized Co2+ ions, while MWCNTs interestingly induced increments in the dielectric constant values. VSM measurements revealed that Co doping induces a clear transformation from the diamagnetic behavior of pure ZnO to ferromagnetic characteristic through Co2+-Vo-Co2+ exchange interactions. 5 wt% MWCNTs/5 wt% Co doped ZnO (5CN/5CoZ) nanocomposite showed the highest sunlight-irradiated photocatalytic activity for degradation of Congo red with degradation efficiency of 96%. The high photocatalytic activity of 5CN/5CoZ nanocomposite was assigned to its visible-light band gap, the presence of electron-hole traps and formation of MWCNTs-ZnO interface. It was found that the degradation of Congo red followed the pseudo-first-order kinetics. The 5CN/5CoZ nanocomposite exhibited the best catalytic efficiency and recyclability with 96%, 92%, and 89% degradation activities for three successive experiments.

Bismuth vanadate/MXene (BiVO4/Ti3C2) heterojunction composite: enhanced interfacial control charge transfer for highly efficient visible light photocatalytic activity.

We have synthesized BiVO4/Ti3C2 nanocomposite via a low-cost hydrothermal method and investigate its photocatalytic degradation activity against monoazo (methyl orange) and diazo dye (Congo red) in an aqueous solution under visible light. The physiochemical characterization exhibited that the addition of MXene in pristine BiVO4 nanocomposite led to an increase in specific surface area and reduction in optical band gap energy. MXene also helps in enhancing visible light response via a higher electron-hole pair generation rate and long lifetime. The synthesized BiVO4/Ti3C2 heterojunction composite exhibited 99.5 % degradation efficiency within 60 min for Congo red and 99.1 % for methyl orange solution in 130 min owed to a large specific surface area (1.79 m2/g), reduced band gap (1.99 eV), and low recombination rate of charge carriers. The chemical mechanism for BiVO4/Ti3C2 nanocomposite proposes that Ti3C2 role-plays as electron capture because of the higher potential of MXenes, tuning band gap energy which paves the way to excellent photocatalytic action. This work opens a new basis for developing Ti3C2 based promising and inexpensive co-catalyst for efficient solar utilization in photocatalytic-related applications in the future.