Electron-hole Separation Research Articles

Construction of Bi2WO6/g-C3N4/Cu foam as 3D Z-scheme photocatalyst for photocatalytic CO2 reduction

Photocatalytic CO2 reduction to hydrocarbon fuels represents a promising solution to CO2 emission challenges. However, photocatalytic CO2 reduction systems face hurdles in practical utilization for the low efficiency of photocatalysts and challenge in catalyst immobilization. Therefore, a novel monolithic three-dimensional Z-scheme photocatalyst was synthesized by fabricating Bi2WO6/g-C3N4 heterojunction on Cu foam substrate (Bi2WO6/g-C3N4/Cu foam) via thermal polymerization and electrophoresis deposition. A series of characterization results, including X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and N2 adsorption–desorption, illustrate the crystalline properties, pore structure, and morphology of the composite photocatalyst. Consequently, Bi2WO6/g-C3N4/Cu foam achieved CO production yield of 33.84 μmol/g cat under visible light illumination for 6 h and retained 96.2 % of initial photocatalytic activity after 30 h of reaction. UV–Vis diffuse reflection spectra, photoluminescence spectra and photoelectrochemical analysis was involved to reveal the mechanism of the photocatalytic activity of composite photocatalyst.The synergistic effect of the Z-scheme mechanism and the hierarchical macroporous structure improves the light absorption, light-induced electron-hole pair separation, and charge transmission. This catalyst construction strategy provides a viable approach for facilitating practical photocatalytic CO2 reduction.

Ternary heterostructure-driven photoinduced electron-hole separation enhanced oxidative stress for triple-negative breast cancer therapy

Zinc oxide nanoparticles (ZnO NPs) stand as among the most significant metal oxide nanoparticles in trigger the formation of reactive oxygen species (ROS) and induce apoptosis. Nevertheless, the utilization of ZnO NPs has been limited by the shallowness of short-wavelength light and the constrained production of ROS. To overcome these limitations, a strategy involves achieving a red shift towards the near-infrared (NIR) light spectrum, promoting the separation and restraining the recombination of electron-hole (e−-h+) pairs. Herein, the hybrid plasmonic system Au@ZnO (AZ) with graphene quantum dots (GQDs) doping (AZG) nano heterostructures is rationally designed for optimal NIR-driven cancer treatment. Significantly, a multifold increase in ROS generation can be achieved through the following creative initiatives: (i) plasmonic Au nanorods expands the photocatalytic capabilities of AZG into the NIR domain, offering a foundation for NIR-induced ROS generation for clinical utilization; (ii) elaborate design of mesoporous core-shell AZ structures facilitates the redistribution of electron-hole pairs; (iii) the incorporation GQDs in mesoporous structure could efficiently restrain the recombination of the e−-h+ pairs; (iv) Modification of hyaluronic acid (HA) can enhance CD44 receptor mediated targeted triple-negative breast cancer (TNBC). In addition, the introduced Au NRs present as catalysts for enhancing photothermal therapy (PTT), effectively inducing apoptosis in tumor cells. The resulting HA-modified AZG (AZGH) exhibits efficient hot electron injection and e−-h+ separation, affording unparalleled convenience for ROS production and enabling NIR-induced PDT for the cancer treanment. As a result, our well-designed mesoporous core-shell AZGH hybrid as photosensitizers can exhibit excellent PDT efficacy.

Fabrication of NiFe-LDH/MoS2 2D/2D material to construct direct Z-scheme heterojunction for enhanced CO2 photocatalytic reduction under visible light irradiation

In recent years, the utilization of solar energy for conversion of CO2 into fuels has emerged as a promising strategy for mitigating the Greenhouse effect. However, transport efficiency of photogenerated carriers plays a crucial role in determining the efficacy of CO2 photocatalytic reaction. In this paper, a 2D/2D composite material consisting of NiFe-LDH/MoS2, presenting high efficiency in separating photogenerated electron-hole pairs, has been successfully synthesized using a straightforward hydrothermal method. XRD, XPS, FTIR and other characterization results proved that the composite was successfully prepared, and its unique direct Z-scheme heterostructure improved the efficiency of CO2 photocatalytic reduction effectively. The composite material NiFe-LDH/MoS2 demonstrated enhanced rate of photo-induced electron-hole pair separation comparing with pure NiFe-LDH. Apart from this, the charge transfer resistance was reduced simultaneously, the composite material exhibited perfect photocatalytic activity. In photocatalytic reduction reaction experiment, CO yield of NiFe-LDH/MoS2 can reach 10.72 μmol/g, which is 3.93-fold and 4.17-fold that of bare NiFe-LDH and MoS2. The cyclic test also shows that the catalyst has good stability under visible light irradiation.

An outstanding photocatalytic performance of CNTs based nanocomposite of ternary metal oxides towards cationic and anionic dyes and pharmaceutical drug

Currently, hetero-metallic oxides and their nanocomposites with 1D materials have a tremendous role in photocatalytic applications, mainly for the removal of organic effluents, due to their higher potential of electron-hole pair migration and separation than pure metal oxide NPs. The present work reports the fabrication of ternary metal oxides nanostructure (WO3·Ag2O·CuO) and its nanocomposite with carbon nanotubes (WO3·Ag2O·CuO/CNTs) using a facile approach i.e. ultra-sonication. The photocatalytic removal efficacy of fabricated nanocomposite i.e. WO3.Ag2O.CuO/CNTs along its counterpart (WO3·Ag2O·CuO) was evaluated using a model cationic dye (Methylene blue, MB), an anionic dye (Congo red, CR), and an analgesic drug (Paracetamol). The catalytic experiment was performed under natural sunlight upon light irradiation of about 90 min and using 30 mg of photocatalyst for all chosen effluents. The obtained results deduced that WO3·Ag2O·CuO/CNTs nanocomposite showed catalytic efficiency of about 97 % for MB, 87 % for CR, and 93 % for Paracetamol while it was about 80 % for MB, 74 % for CR, and 79 % for drug using WO3·Ag2O·CuO as photocatalyst. The rate constant values of nanocomposite for the removal of MB, CR, and Paracetamol are 0.037 min−1, 0.023 min−1, and 0.027 min−1 respectively. The remarkable degradation performance of WO3·Ag2O·CuO/CNTs nanocomposite as compared to ternary metal oxide (WO3·Ag2O·CuO) was due to its high charge separation, high surface area, and availability of large number of active sites for the adsorption of pollutant molecules. Hence, WO3·Ag2O·CuO/CNTs nanocomposite could be a competent photocatalyst for the removal of variety of industrial effluents i.e. organic dyes and pharmaceutical drugs etc.

Accelerated sonochemical fabrication of MIn2S4 (M = Zn, Mg, Ni, Co) for ultra-high photocatalytic hydrogen peroxide production

Ternary metal sulfide (MIn2S4) by virtue of large extinction coefficient, suitable band gap and stability, has been proposed as a candidate for photocatalytic synthesis hydrogen peroxide (H2O2). However, MIn2S4 is conventionally synthesized by solvothermal method that is generally characterized by tedious operational steps and long reaction time. In this work, four sonoMIn2S4 (M = Zn, Mg, Ni, Co) were successfully prepared by sonochemical method within 2 h. These as-synthesized sonoMIn2S4 delivered much high-efficient photocatalytic H2O2 generation. Particularly, the sonoZnIn2S4 presented H2O2 production rate of 21295.5 μmol∙g−1∙h−1 in water/benzylalcohol system, which is 3.0 times that of ZnIn2S4 prepared by solvothermal method. The remarkably improved photocatalytic performance of sonoZnIn2S4 might be due to the multiple defects and fast electron-hole pair separation caused by ultrasound cavitation effect. Other metal sulfide photocatalysts with high performance were efficiently fabricated by facile sonochemical technology as well. The sonochemical method realized the rapid preparation of metal sulfide photocatalysts and efficient production of H2O2, which benefits to meet the United Nations Sustainable Development Goals (SDGs) including SDG-7 and SDG-12.

Robust in-plane ferroelectricity, high hole mobility, and low thermal conductivity in GeO monolayer: A first-principles study

Motivated by the experimental advancements in 2D crystalline germanium oxides, we investigated the electronic and transport properties of GeO and GeO2 monolayers (MLs) using first-principles calculations. GeO ML exhibits an in-plane ferroelectricity until the melting point of 1100 K. Compressive strain facilitates polarization reversion by lowering the ferroelectric transition barrier. The band edges meet the requirements for photocatalytic water splitting across a wide variety of strains. Meanwhile, GeO ML has a high hole mobility of 4854 cm2/V⋅s along the y-axis, owing to its low deformation potential constant. The large difference in hole and electron mobility promotes electron–hole separation. In addition, GeO ML has a low thermal conductivity of κx = 3.37 W/mK and κy = 12.53 W/mK at 300 K, due to the strong anharmonicity caused by lone-pair electrons. In contrast, GeO2 ML has an isotropic electron mobility of 382 cm2/V⋅s and an κ of 22.60 W/mK at 300 K. At last, we discussed the probable reaction to grow 2D GeO crystal and calculated the Raman intensity to distinguish it in future experiments. Our results show that 2D GeO has potential applications in ferroelectrics, thermoelectrics, and water splitting.

Enhancement of microplastics degradation with MIL-101 modified BiOI photocatalyst under light and dark alternated system

The composite material combining BiOI with metal-organic frameworks, was developed as catalyst for microplastics degradation. The preparation was modified to achieve the optimal composite catalyst BiOI/MIL-101–40%. The composites exhibited a larger surface area, superior photo-activity, and a distinct heterojunction structure, which accelerated the separation of electrons and holes. Besides, the inclusion of Fe(II) within MIL-101 could construct a photo-Fenton reaction upon the addition of H2O2 in the solution. The carbonyl index of treated polyethylene microplastics increased by 0.127 after 6 h reaction, which was 5.3 and 3.7 times higher than monomer BiOI and MIL-101, respectively. Efficient electron-hole separation and Fe(III)/Fe(II) conversion improved the rate-limiting step of the Fenton process, leading to a synergistic effect between photocatalysis and Fenton reaction, significantly enhancing PE degradation efficiency. Electron spin resonance spectroscopy and selective radical quenching experiments were performed to detect the active components, and the main active species proved to be the hydroxyl radical and the hole. The band structure of the photocatalyst and intermediate products in the reaction solution were subsequently analyzed, leading to the inference of potential reaction mechanisms and pathways. The catalyst-built Fenton system demonstrated outstanding proficiency even under alternating light and dark conditions. The extracted microplastic samples also confirmed the feasibility of this system for complex samples. In conclusion, this study highlighted a green and efficient approach that may be used in future industrial applications to combat microplastic pollution.

Small‐Bandgap Transducers Induced Carrier Separation for In Situ Dual‐Amplified Tumor Oxidative Stress

AbstractThe inherent and unique charge‐carrier release characteristics of piezoelectric sonosensitizers with desired bandgap can be leveraged to initiate reactive oxygen species (ROS) reactions that have considerable potential for sonodynamic therapy (SDT). In this study, a bimetallic Bi4NbO8Br‐polyvinylpyrrolidone (BNOBP) with a small bandgap (2.45 eV) is synthesized as a potential piezoelectric sonosensitizer. The robust interactions within and between the Bi─O and Nb─O layers narrow the bandgap, facilitating carrier transfer. Concurrently, compared with that of TiO2 and BiOBr, BNOBP exhibits a rapid acoustoelectric response and desirable electron–hole separation efficiency, enabling the generation of ·O2− under ultrasound (US) irradiation. Notably, BNOBP alleviates the overexpression of glutathione (GSH) in tumors and prevents the consumption of the generated ROS by GSH. Combining the previous small bandgap endow the high ROS generation efficiency, this study provides a paradigm for in situ regulation of oxidative stress levels in tumor tissue microenvironment based on bimetallic piezoelectric sonosensitizers.

Construction of a Dual-Function Mo-ZIS@Ti for Photocatalytic Benzyl Alcohol Oxidation and Hydrogen Evolution Performance.

The photocatalytic oxidation of benzyl alcohol and the simultaneous evolution of hydrogen from water are efficient dual-optimal routes. It is important to develop composite catalysts that combine redox properties and facilitate electron-hole separation and transport. Herein, the bimetallic-doped Mo-ZIS@Ti photocatalyst was designed and synthesized, and the selective oxidation of benzyl alcohol and hydrogen evolution by water splitting was realized at the same time. Under visible light irradiation, benzyl alcohol was completely converted with more than 99% selectivity for benzaldehyde, and the H2 production rate was 5.6 times higher than the initial ZIS. The exceptional catalytic performance was ascribed to utilizing Ti-MIL-125 as a precursor, wherein slowly releasing-doped Ti formed robust Ti-S bonds that quickly transfer electrons and reduce sites. Meanwhile, doping Mo effectively captures photogenerated holes and acts as active sites for oxidation reactions. Both experimental characterization and work function calculations demonstrate that the bimetallic synergism effectively modulates the electronic structure of ZIS, promotes the directional separation of electrons and holes, and significantly improves the photoactivity and stability of ZIS. This work contributes a route to obtain benzaldehyde and green hydrogen at the same time and also gives new insights for the construction and mechanism study of bimetallic-doping catalysts.

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.

Covalent copper-organic frameworks with light-activable catalytic centers as smart artificial enzymes for highly sensitive and wide-range biocatalytic diagnosis

As a popular sensing method, colorimetric biosensing has the advantages of convenient operation, low cost, fast response, and easy readout. However, due to the complex structure of nanomaterials, low catalytic activity, and unclear catalytic mechanisms, constructing efficient, stable, and specific artificial biocatalysts for colorimetric biosensing is still a challenge. In this study, to propose a new colorimetric biosensing system, we synthesize three different types of copper cyclic trinuclear unit-based 2D copper-organic frameworks (CuOFs) with covalent structures and light-activable catalytic centers to serve as smart artificial enzymes for highly sensitive and wide-range biocatalytic diagnosis. By varying the light absorption centers, CuOFs with different band structures, light absorption capacity, photoelectron transfer efficiency, and electron-hole pair separation efficiency can be obtained. Of the three covalent CuOFs, tris(4-aminophenyl)amine (Tpa)-Cu3 exhibited the widest light absorption range, the narrowest band gap, the smallest electron transfer barrier, and the best-photoinduced charge separation efficiency, which was conducive to improving the light capture ability and eventually improving the photocatalytic properties. Further tests demonstrated that Tpa-Cu3 exhibited the best peroxidase-like activity under visible light irradiation, which could effectively diagnose the glucose and common antioxidants with a wider detection range and lower detection limit than many previously reported biocatalytic materials. We expect this design will provide new insights into enzyme-like organic framework materials and unique systems for high-sensitive and wide-range colorimetric detection for future biocatalytic applications.

Efficient photocatalytic nitrogen fixation via oxygen vacancies in Zr-MOFs at ambient conditions

Photocatalytic nitrogen fixation is seen to be a potential technology for nitrogen reduction due to its eco-friendliness, low energy consumption, and environmental protection. In this study, photocatalysts with abundant oxygen vacancies (Zr-naphthalene dicarboxylic acid (Zr-NDC) and Zr-phthalic acid (Zr-BDC)) were designed using 1,4-naphthalene dicarboxylic acid (H2NDC) and 1,4-phthalic acid (H2BDC) as ligands. Since the structure of H2NDC includes one extra benzene ring than H2BDC, the charge density differential of the organic ligand is probably altered. The hypothesis is proved by density function theory (DFT) calculation. The abundant oxygen vacancies of the catalyst offer numerous active sites for nitrogen fixation. Concurrently, the process of ligand–metal charge transfer facilitates photo-electron transfer, creating an active center for nitrogen reduction. Additionally, the functionalization of ligand amplifies another pathway for charge transfer, broadening the light absorption range of Metal-organic framework (MOF) and increasing its capacity for nitrogen reduction. In contrast to H2BDC, the benzene ring added in H2NDC structure acts as an electron energy storage tank with a stronger electron density difference favorable for photogenerated electron-hole separation resulting in higher photocatalytic activity in Zr-NDC. The experimental results show that the nitrogen fixation efficiency of Zr-NDC is 163.7 µmol g−1h−1, which is significantly better than that of Zr-BDC (29.3 µmol g−1h−1). This work utilizes cost-effective and non-toxic ingredients to design highly efficient photocatalysts, thereby significantly contributing to the practical implementation of green chemistry principles.

Experimental and theoretical studies on the photoelectrocatalytic property of titanium dioxide nanoarrays improved by S,N co-doped graphene quantum dots

In this paper, sulfur and nitrogen co-doped graphene quantum dots (S,N-GQDs) were compounded with titanium dioxide (TiO2) nanorods by chemical surface modification. S,N-GQDs in diameter of 5 nm are uniformly distributed on the surface of TiO2 nanorod arrays. The presence of CS bonds in S,N-GQDs not only broaden the absorption of visible light by GQDs, but also enhanced the visible light absorption of S,N-GQDs/TiO2 composites. The photocurrent densities of S,N-GQDs/TiO2 were 3.66 times that of unmodified TiO2. The calculation results of density functional theory (DFT) showed that the band gap of S,N-GQDs is significantly reduced compared to GQDs, indicating that electrons are more likely to transit to higher energy levels and form more activation sites. Moreover, compared with TiO2, the DFT calculation results of band gap, density of states and charge density difference of S,N-GQDs/TiO2 showed that S,N-GQDs/TiO2 had a wide wavelength of visible light absorption and better electron-hole separation ability, resulting in the superior photoelectrocatalytic property. This research provides favorable analytical value for the development of photocatalysts based on heterostructures.

Sub-Band Assisted Z-Scheme for Effective Non-Sacrificial H2O2 Photosynthesis.

Photosynthesis of H2O2 from earth-abundant O2 and H2O molecules offers an eco-friendly route for solar-to-chemical conversion. The persistent challenge is to tune the photo-/thermo- dynamics of a photocatalyst toward efficient electron-hole separation while maintaining an effective driving force for charge transfer. Such a case is achieved here by way of a synergetic strategy of sub-band-assisted Z-Scheme for effective H2O2 photosynthesis via direct O2 reduction and H2O oxidation without a sacrificial agent. The optimized SnS2/g-C3N4 heterojunction shows a high reactivity of 623.0µmolg-1h-1 for H2O2 production under visible-light irradiation (λ>400nm) in pure water, ≈6 times higher than pristine g-C3N4 (100.5µmolg-1h-1). Photodynamic characterizations and theoretical calculations reveal that the enhanced photoactivity is due to a markedly promoted lifetime of trapped active electrons (204.9ps in the sub-band and >2.0ns in a shallow band) and highly improved O2 activation, as a result of the formation of a suitable sub-band and catalytic sites along with a low Gibbs-free energy for charge transfer. Moreover, the Z-Scheme heterojunction creates and sustains a large driving force for O2 and H2O conversion to high value-added H2O2.

Organic polymer/inorganic heterostructure coupled with efficient allosteric bicycle strand displacement for photochemical sensing

In this work, a high-performance conjugated microporous polymer (CMP) decorated with BiOBr (Tr(PhXOD)3-CMP/BiOBr) is synthesized to application in construction of ultrasensitive photoelectrochemical (PEC) biosensor for sensing miRNA-122, by firstly coupling with efficient clip toehold-mediated allosteric bicycle strand displacement (ABSD). Notably, the Tr(PhXOD)3-CMP/BiOBr not only owns self-enhanced D-A-D structure that extremely shortens migration distance of photo-generated electron, but also forms Z-type heterostructure for accelerating electron-hole separation, thereby significantly enhancing the photocurrent with 10-fold higher than commonly used methods. Meanwhile, the clip toehold-mediated ABSD based on ternary linkage structure transformation avoids the attrition of invading strand, endowing the conservation of high concentration for undergoing rapid reaction with high-efficiency DNA amplification, which dramatically improves reaction time and superior target conversion. The experimental results indicate that proposed PEC biosensor had a high sensitivity to miRNA-122 with a detection limit of 0.49 fM, which provides a newly organic/inorganic photosensitive nanomaterials and efficient DNA strand displacement in bioanalytical and early clinical disease diagnosis.

Twisted leaf like ZnO-flake-like BiOI@CNF grown on ITO substrate as a nanostructured pioneering platform for photoelectrochemical water splitting

Despite ZnO nanostructures garnering significant attention for photoelectrochemical (PEC) water splitting, the quest for efficient ZnO-based photoelectrodes with optimal light absorption, effective electron-hole separation, and transfer remains a challenge. The formation of ZnO heterojunctions with lower bandgap nanostructures of semiconductors has emerged as a strategy to enhance charge transfer while mitigating recombination rates. Additionally, the introduction of carbon nanofibers (CNFs) to these heterojunctions serves to further suppress recombination by electron trapping and enhances catalytic active sites, thereby elevating PEC performance. In this study, twisted leaf-like ZnO, flake-like BiOI, ZnO-BiOI nanostructure heterojunctions, and ZnO-BiOI@C composites were synthesized through a solvothermal method. Notably, the ZnO-BiOI@C photoelectrode exhibited outstanding performance, achieving a photocurrent density of 5.6 mA/cm2 through linear sweep voltammetry under light illumination. Each synthesized photoelectrode demonstrated robust photocurrent responsiveness and excellent stability under chopped conditions for up to 1150 s with a 50 s interval. This remarkable stability is attributed to the unique and stable morphological characteristics and strong crystallinity of the synthesized materials. The formed heterojunction between ZnO-BiOI was found to extend light absorption capabilities, while the incorporation of CNFs effectively trapped electrons from the heterojunction's conduction band, enhancing overall water splitting performance. The results underscore the potential of the ZnO-BiOI@C composite as a high-performing photoelectrode for PEC applications, emphasizing the importance of morphological and compositional considerations in advancing PEC technologies.

Oxygen vacancies nanoarchitectonics in BiVO4/WO3 heterostructured photoanode for effective berberine wastewater purification and electricity generation

BackgroundPhotoanode, as a key component of the photocatalytic fuel cell, still faces challenges for high-efficiency wastewater treatment and synchronous electricity generation, owing to low electron-hole separation efficiency and light response. MethodsOxygen vacancies were rationally introduced on BiVO4/WO3 (OV-BiVO4/WO3) as visible-light-responsive photoanode, through a simple two-step hydrothermal method. The favorable activities were primarily derived from the synergistic effects of the oxygen vacancies and heterojunction, which extended the light adsorption range and significantly improved the separation ability of photogenerated carriers, revealing by comprehensive experiments and theoretical calculations. Significant FindingsCompared with WO3, BiVO4 and BiVO4/WO3, OV-BiVO4/WO3 exhibited highest berberine degradation rate (97.7 %, 120 min) and maximum power density (0.42 mW cm−2). Further, the influence of water conditions on photocatalytic performance was explored considering the complexity of actual wastewater. The findings evidenced that ·OH and ·O2− mainly participated in antibiotic decomposition. The photocatalytic reaction mechanism and berberine degradation pathway over OV-BiVO4/WO3 were proposed. This study emphasizes the importance of oxygen vacancies engineering controlling over the surface catalytic performance of photoelectrode and electricity generation, and illustrates the potential of for water remediation and energy production.

Photogenerated carriers transfer in Pd/TiO2-AgO heterojunction and its photocatalytic behaviors on oxidative dehydrogenation of ethane to ethylene

Photocatalytic oxidative dehydrogenation of ethane to ethylene with a high selectivity is an attractive reaction. In this study, different types of heterojunctions between Pd/TiO2 and a second metal oxide semiconductor were designed and synthesized to realize high activity conversion of C2H6 to C2H4. Pd/TiO2-AgO heterojunction was proved with best reaction performance. The addition of AgO facilitated the activation of reactant molecules. It enhanced directional transfer of electron-hole pairs and separation efficiency of photogenerated carriers. Pd/TiO2-5 % AgO heterojunction was proved with the best separation ability of photogenerated carriers and the largest number of surface hydroxyl groups. Detailed charge transfer path and reaction mechanism were proposed and discussed.

Facile preparation of ZIF-67 on TiO2 and enhancement photocathodic protection for 316L stainless steel

Photocathodic protection (PCP) anticorrosion using sunlight is a green and sustainable technology. However, the ease of carriers compounding and the low light utilization are still the main restraints to its development. To develop an effective photoanode, a metal-organic framework (MOF, i.e., ZIF-67) material is electrodeposited and grown in-situ on TiO2 nanorods. The morphological structure, light absorption properties, photoelectrochemical properties and cathodic protection principle of ZIF-67/TiO2 photoanode are analysed by SEM, PL, I-V and EIS. The material characterization and light absorption characteristics show that the photoanode has good light absorption performance and higher electron hole separation efficiency. Photoelectrochemical test shows that ZIF-67/TiO2 photoanode has excellent photocathodic protection for 316L stainless steel (316L SS). ZTRs-60 has the optimal protection effect. Under simulated sunlight, the OCP of 316L SS coupled ZTRs-60 is -0.41 V vs. Ag/AgCl, and the current density of the I-t curve can reach 20 μA/cm2. EIS and Tafel tests show that the photogenerated electrons transfer to the stainless steel surface, which promotes the cathode polarization process and alleviates the metal corrosion.

BaTi0.85Zr0.15O3/MOF-5 nanocomposite: Synthesis, characterization and photocatalytic activity toward tetracycline

It has been proposed that oriented anchoring strategies can be used to organize BaTi0.85Zr0.15O3 (BTZ) quantum dots (QD) with MOF-5 to provide highly efficient catalytic degradation of tetracycline (TC). This study presents the preparation of [Zn4O (BDC)3] (BDC = benzene-1,4dicarboxylate) metal–organic framework-5 (MOF-5)/BTZ nanocomposites by a facile one-pot solvent-thermal precipitation method. The as-synthesized samples were identified by XRD, TG-DTG, UV–VIS DRS, FESEM, FTIR, BET, TEM, PL, and EDX characterization techniques. The photocatalytic ability of nanocomposite BTZ (30 %wt)/MOF-5 was particularly impressive among the binary photocatalysts. In a 10 ppm solution of TC, BTZ (30 wt%)/MOF-5 demonstrated superior photodegradation activity, with 95 % degradation efficiency of TC determined by HPLC. The best response was achieved at pH 11 with catalyst dosages of 0.2 g/L, irradiation time of 150 min, and CTC of 10 ppm. An internal electric field was suggested to mediate the direct Z-scheme charge transfer mechanism between BTZ and MOF-5. The improvement was achieved by fabricating BTZ and MOF-5 in an indirect Z-scheme heterojunction system. Photogenerated electron-hole separation can be accelerated by BTZ/MOF-5 with improved redox capabilities. Overall, taking advantage of an enhanced redox capacity under ultraviolet (UV) light irradiation, this study demonstrates how to promote efficient antibiotic degradation using MOF-based nanocomposites. Moreover, photodegradation kinetics were studied using the Hinshelwood formula, giving 0.0113 min−1 (slope) and 61.32 min as t1/2. In the COD experiment, mineralized TC molecules had y = -0.0144 + 0.0444x, r2 = 0.9942, and k = 0.0144 min−1 (t1/2 = 48.12 min).