Optimal Photocatalyst Research Articles

In-situ construction and exciting photocatalytic performance of broad-spectrum responsive BiO2-x/Bi2O2CO3 heterojunctions in tetracycline degradation.

The wastewater polluted by antibiotics is very harmful and dangerous since these contaminants are poisonous and cannot occur by self-degradation. Research has verified that photocatalytic degradation is an effective strategy for addressing this issue; thus, developing a promising photocatalyst is indispensable. In this work, BiO2-x/Bi2O2CO3 nanosheet heterojunctions were constructed with an in-situ growth method, and their structure-photocatalytic performance relationships in degrading tetracycline (TC) were elucidated in detail. Compared with the pristine BiO2-x and Bi2O2CO3, the resulting heterojunctions broadened the spectral response range and exhibited reduced electron-holes recombination, therefore improving photocatalytic performance even irradiated by near-infrared light. In the presence of the optimal 1:3 BiO2-x/Bi2O2CO3 (20 mg), 86% of TC (50 mL, 10 mg L-1) could be removed under visible light, which is obviously greater than that by BiO2-x (56%) and Bi2O2CO3 (54%). Also, the optimal photocatalyst exhibited satisfactory cyclic stability in the elimination of TC. In addition, the proposed procedure for TC degradation and the plausible photocatalytic mechanism were presented. This work offers a straightforward approach for fabricating highly effective photocatalysts for eliminating antibiotic-based contaminants in water.

Functionalized cements incorporated with nanocomposite photocatalysts for self-cleaning applications

The constantly escalating pollution on the surface of cement-based materials affects architectural aesthetics and residents′ health, necessitating frequent cleaning and maintenance, which contradicts the concept of sustainable development. This study aimed to develop a novel photocatalytic cement material to enhance the self-cleaning capabilities of cement-based materials, thereby extending their service life and reducing maintenance costs. To achieve this, carbon quantum dots (CDs) and g-C3N4 (CN) nanocomposite photocatalysts (CDs@CN) were synthesized and integrated into white cement to prepare photocatalytic cements. The materials were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy. Photocatalytic performance was evaluated by the degradation of Rhodamine B (RhB) under xenon (Xe) lamp, Vis light and UV light. The CDs@CN nanocomposite displayed superior photocatalytic activity, particularly under Xe lamp irradiation, achieving over 95 % degradation of RhB within 1 h. Even under Vis and UV light, the photocatalytic cement retains robust self-cleaning capabilities, achieving pollutant degradation rates of 81 % and 63 %, respectively, within 1 h. This performance exceeded that of pristine CN and control samples, demonstrating effective light absorption and charge separation. The optimal photocatalyst concentration in cement was identified as 0.1∼5.0 wt%, balancing performance and dispersion. The developed CDs@CN-based photocatalytic cement material offers a sustainable solution for self-cleaning and environmental purification. This study provides insights into the design of functional cementitious materials and contributes to the sustainable development of the construction industry.

Efficient photocatalytic degradation of microplastics by constructing a novel Z-scheme Fe-doped BiO2−x/BiOI heterojunction with full-spectrum response: Mechanistic insights and theory calculations

Recently, microplastics (MPs) have garnered significant attention as a challenging emerging pollutant to address. Here, a full-spectrum light-driven Fe-doping BiO2−x/BiOI (FBI) Z-scheme heterojunction was constructed for efficiently degrading MPs in waters. Compared with BiO2−x, Fe doping BiO2−x, and BiOI, the optimal photocatalyst (40-FBI) can cause deep cracks in the polyethylene terephthalate (PET) within 10 h under the irradiation of full-spectrum light. Meanwhile, FT-IR characterization revealed that the absorption peak intensities of the C-O group, CO group, -CH stretching vibration, and -OH group on the MPs surface gradually increased with degradation time. A series of experiments and theory calculations revealed that the introduction of Fe creates impurity levels, accelerating the separation of photo-generated carriers and reducing the work function of BiO2−x, thereby enhancing the transport of photo-generated carriers between Z-scheme heterojunctions. This study offers a valuable idea for designing an efficient photocatalyst by simultaneously introducing ion doping and constructing heterojunctions for enhancing MPs degradation.

Interfacial Bi-O-C bonds and rich oxygen vacancies synergistically endow carbon quantum dot/Bi2MoO6 with prominent photocatalytic CO2 reduction into CO

Developing the photocatalysts with the low charge-transfer resistance and fast charge kinetics is crucial to photocatalytic CO2 reduction into hydrocarbon fuels. Herein, we depict the interfacial Bi-O-C bond-bridged carbon quantum dot (CD)/oxygen vacancy-rich Bi2MoO6 (VOR-BMO) Ohmic junction photocatalysts. They were constructed by in-situ anchoring carbon quantum dots (CDs) onto the VOR-BMO hierarchical petal-like structures (HPs), which are self-assembled from numerous nanosheet subunits. Experimental analysis together with density functional theory (DFT) calculations indicate that the Bi-O-C bonds can provide the atomic-level interfacial channels, and introducing rich oxygen vacancies (VOs) into the BMO HPs can induce the enhanced built-in electric field (IEF) of the Ohmic heterojunction formed between VOR-BMO HPs and CDs, synergistically contributing the eminent charge transfer kinetics, so as to sharply boost the separation and transfer of the photoinduced electrons of VOR-BMO HPs into CDs with a near-zero resistance; Besides, the CD/VOR-BMO heterostructures can not only change the endoergic rate-determining step of VO-poor (VOP)-BMO HPs (i.e., CO* desorption to form CO) to an exoergic reaction process, thus promoting the CO* desorption from the photocatalyst surface, but also decrease the overall activation energy barrier. Consequently, in the presence of H2O vapor with no sacrificial agent, the optimum photocatalyst (CD/VOR-BMO-1.2) exhibits the fantabulous performances of CO2 photoreduction into CO with the production rate and selectivity of 60.00 μmol·g−1·h−1 and near 100 %, respectively. Such performances are comparable with the most recently reported photocatalysts for CO2 conversion. The study offers a valid strategy that harnesses the synergistic effect of the interfacial chemical bonds and Vo-induced enhanced IEF to design the high-efficiency photocatalysts for both energy and environmental applications.

Engineering polydopamine-functionalized NH2-MIL-125 (Ti) for tetracycline degradation and antibacterial applications

Methods for the precise construction of NH2-MIL-125 (Ti) with chemical bonding are indispensable for the synthesis of MOF-based photocatalytic materials, which possess high activity, stability and biocompatibility. Herein, polydopamine (PDA)-functionalized NH2-MIL-125 (Ti) was prepared using cross-linking reaction between catechol groups in PDA and amine groups in NH2-MIL-125 (Ti), instead of the self-polymerization process. The conjugation of functional groups had strong chemical bonding interactions. Benefiting from the assembly of PDA, the optimum photocatalyst presented superior tetracycline (TC) degradation efficiency, as well as 99.9 % and 99.4 % antimicrobial rates against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. The possible photocatalytic mechanisms of TC degradation and antibacterial activity were proposed and verified by EPR results. This work provides in-depth scientific insights for photocatalysis and biomedical field.

Efficient photocatalytic degradation of ciprofloxacin using floating α-NiMoO4/mpg-C3N4/EP under visible light

Conventional water treatment processes often fail to effectively remove antibacterial drugs, necessitating advanced strategies. This study presents the synthesis of novel floating, visible light-active α-NiMoO4/mpg-C3N4/EP composites for the removal of ciprofloxacin (CFX), a widely used quinolone antibiotic, from water. These composites are easily recoverable, highly stable, and demonstrate excellent reusability. The optimal photocatalyst, NC-101/EP (α-NiMoO4/mpg-C3N4 = 10:1), achieved 96.2 ± 1.1% degradation of CFX at 1.6 g L−1 within 80 min under visible light, significantly outperforming previous benchmarks. This high efficiency is attributed to the formation of interfacial junctions and a built-in electric field, which enhanced charge transfer and hydroxyl radical generation through an S-scheme mechanism. Fluorescence spectroscopy provided precise monitoring of CFX degradation without interference from coexisting intermediates. Density functional theory (DFT) calculations revealed that hydroxyl radicals initiated highly favorable and spontaneous oxidation of CFX, with a reaction rate constant of 6.04 × 109 M−1 s−1. The preferred oxidation pathway followed the sequence: HO-addition > H-abstraction > single electron transfer. Four degradation pathways were identified, with key intermediates confirmed by high-resolution mass spectrometry. The process also significantly reduced CFX toxicity, ensuring minimal environmental impact. These findings position NC-101/EP as a promising photocatalyst for large-scale water treatment applications targeting antibiotic contamination.

Sodium thiosulfate modified graphitic carbon nitride for enhancing the photocatalytic production of aldehydes

The oxidation of alcohols to aldehydes is one of the most relevant reactions in organic chemistry. The currently implemented methods based on expensive noble metallic catalysts, toxic solvents, and high temperature and pressure conditions have released the seek for softer and cheaper alternatives such as photocatalysis. In this sense, graphitic carbon nitride has been modified with sodium thiosulfate as a source of S and Na+ incorporation in the structure, aimed at enhancing the photocatalytic performance on the oxidation of alcohols to aldehydes, i.e. cinnamaldehyde, benzaldehyde, and vanillin in aqueous solution. Three g-C3N4 samples synthesized from different precursors, i.e. melamine, thiourea, and urea, were treated with sodium thiosulfate. Urea led to the g-C3N4 with the highest mesoporosity (surface area, 69 m2 g−1) and photocatalytic activity. The modification with 5 % (wt.) of Na2S2O3 enhanced the pseudo-first order rate constant of cinnamyl alcohol oxidation from 0.265 h−1 (bare sample) to 0.792 h−1 (Na2S2O3-modified). The characterization of the material suggests a better charge separation of the photogenerated charges after S and Na+ incorporation in the structure, minimizing the recombination rate of photogenerated charges. The optimum photocatalyst, tested in aqueous solution, was most selective in the production of benzaldehyde (selectivity, >100 %) > cinnamaldehyde (>23 %) > vanillin (∼5 %). The selectivity was considerably boosted under acetonitrile as the solvent medium, raising in the case of cinnamaldehyde the 23 % recorded in water to 51 % in pure acetonitrile. The degradation mechanism suggests a strong influence of the photogenerated holes and the superoxide radical, the latter being more selective in the oxidation of the alcohol.

Boosting hydrogen evolution performance of nanofiber membrane-based composite photocatalysts with multifunctional carbon dots

Recent progress in the co-spinning of nanofibers and semiconductor particles offers a promising strategy for the development of photocatalytic devices, solving aggregation and catalyst recovery challenges. However, composite photocatalysts based on nanofiber membranes often suffer from poor conductivity, low hydrophilicity, and easy recombination of photogenerated electron-hole pairs in the semiconductor components. Here, to tackle the aforementioned issues of ZnIn2S4/polyacrylonitrile (ZIS/PAN) nanofiber-based catalysts, we prepared a composite carbon dots/ZnIn2S4/polyacrylonitrile (CZP) nanofiber membrane by blending carbon dots (CDs) with ZIS/PAN using the electrospinning process. The hydrogen evolution performance of the CZP photocatalyst was significantly improved by CDs, which enhanced the hydrophilicity, increased the light absorption, facilitated the transfer of photogenerated electrons, and reduced the recombination of photogenerated electron-hole pairs. Notably, the optimal CZP photocatalyst achieved a hydrogen evolution rate of 2250 μmol g-1h−1, which is about 23 % higher than that of the nanofiber membrane without CDs and 4.55 times higher than that of ZIS particles. The present work successfully improved the CZP nanofiber membrane of photocatalytic hydrogen evolution performance, and the membrane may benefit further device development by eliminating the need for stirring and simplifying the recovery process.

Construction of multi-functional S-Vacancy-Zn3In2S6/Bi-MOF S-scheme heterojunction containing interfacial chemical bonds for the efficient photocatalytic production of H2O2 and excellent photocatalytic degradation of OTC and TC

Designing outstanding S-scheme heterojunction photocatalysts for eliminating pharmaceutical pollution and energy dilemmas is an effective strategy for tackling the issue of global environmental pollution. Herein, the Zn3In2S6/Bi-MOF S-scheme heterojunction was prepared through a facile in-situ hydrothermal method. The Bi-S bonds were introduced into the interface of an S-vacancy-containing Zn3In2S6/Bi-MOF S-scheme heterojunction, which profoundly boosts migration and separation of photogenerated carriers as the highway for electron transfer. The practical significance of Zn3In2S6/Bi-MOF composites for environmental pollution control was assessed using oxytetracycline (OTC) and tetracycline (TC) as representative pharmaceutical pollutants. Simultaneously, the production performance of H2O2 as a new energy carrier was also evaluated to determine the multi-functionality of the Zn3In2S6/Bi-MOF composite. The H2O2 production rate of optimal proportion photocatalyst reaches 3689.94 μmol/g/h without using the sacrificial agent. In addition, it exhibited a photocatalytic degradation of OTC and TC efficiency of 88.1 % and 65.2 % within 60 min, respectively. The Zn3In2S6/Bi-MOF photocatalytic not only exhibits excellent cyclic stability but also has exceptional anti-interference properties-systematic elucidation of the effects of catalyst dosage, pH, and co-existing substances. The efficient photocatalytic production of H2O2 and the degradation of OTC/TC through Bi-S bonds and VS-modificatory S-scheme charge transfer offer valuable new perspectives for designing photocatalysts.

Fabrication of Ag2MoO4/CuWO4 Nanocomposite Photocatalyst for the Degradation of Rhodamine‐B

AbstractHerein, we investigate the photocatalytic properties of a new Ag2MoO4/CuWO4 composite. Three different composites with 5, 10, and 15 weight percent of fine Ag2MoO4 nanostructures were precipitated on CuWO4 nanoparticles. Given the staggered valence and conduction band positions of the two components, the composite with the 10 % weight percent Ag2MoO4 loading on CuWO4 demonstrated the slowest recombination kinetics. The same composite also exhibited the best photocatalytic degradation of RhB under UV light irradiation. The photocatalytic turnover frequency of this composite was also among the best reported for RhB degradation reported in the literature. Photocatalytic kinetics, active species trapping, and various control experiments were carried out to get an insight into the photocatalytic mechanism. The optimum photocatalyst exhibited its highest activity at pH 3 and a RhB degradation turnover frequency (photocatalytic activity) comparable to the best values reported in the literature.

Ultrafast carrier dynamics triggered by Ga-S bond in GaZnON/CdS heterojunction for efficient photocatalytic hydrogen evolution

Constructing heterojunction has been regarded as a valid strategy of photocatalysts to promote the catalytic process. However, beyond the possible synergistic advantage from the component catalysts, the understanding of the interface effect on the photocatalytic process within heterojunction remains challenging. Herein, we prepare a novel GaZnON/CdS heterojunction photocatalyst via a robust electrostatic assembly method. The sulfur atoms in CdS are found to occupy the nitrogen vacancy over the GaZnON surface to form interfacial Ga-S bonds, which is proved as electron-transfer channel between CdS and GaZnON to realize efficient photo-induced carrier separation. The dynamic study quantificationally reveals interfacial electron transfer with a fast transfer rate of 143.8 ns−1. Thereby, the optimal composite photocatalyst reached an impressive hydrogen evolution rate of 14.76 mmol g-1h−1, as well as an impressive AQY of 36.1 % (450 nm). This work expounds the ultrafast carrier dynamics underlying interface bonds within heterojunction for weakened photo-induced carrier recombination.

Solid-state NMR of active sites in TiO2 photocatalysis: a critical review

Titanium dioxide (TiO2) is one of the optimal semiconductor metal oxide photocatalysts with a wide range of application fields, such as heterogeneous catalysis, energy science, and environmental science. Solid-state nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for characterizing both structure and dynamics at an atomic-molecular level in heterogeneous catalysts. In this review, we first provide a brief discussion on the progress in investigating the structures of titanium and oxygen in bulk and on the surface of TiO2 by using various solid-state NMR techniques. Advances in the understanding of electronic structure and properties of TiO2 with distinct surface features, including various crystal facets and heteroatomic adsorption by chemical probe-assisted NMR techniques, are secondly presented. The solid-state NMR characterization of heteroatom active sites (such as 13C, 15N, 11B, 27Al) and their function in TiO2 photocatalysts is described in detail. Finally, a critical discourse assesses the current limitations and prospects of solid-state NMR in its application to the optimization and design of advanced TiO2 photocatalysts.

Metal organic framework-assisted copper-modified titania (Cu/TiO2) with abundant exposed active sites and highly accessible pore channels for an enhanced photo-generation of hydrogen

Metal-doping is a common strategy for establishing active sites on photocatalyst, but appropriately exposing them for maximized atomic utilization remains a great challenge in photocatalytic research. Herein, we propose a metal organic framework (MOF)-assisted approach to synthesis copper-modified titania (Cu-TiO2/Cu) photocatalyst with homogenously distributed and highly accessible active sites in its matrix. Significantly, an MOF precursor, namely NH2-MIL-125, with co-chelation of titania (Ti) and copper (Cu) was subjected to mild calcination, subsequently results in Cu-modified TiO2 with highly accessible channels to its inner surface. These channels provide not only a large reactive surface (>400 m2 g-1); they also enable facile modifying route for the pre-deposited Cu in prior to photoreaction. Specifically, NH3 treatment was applied to partially reduce deposited Cu ions (Cu+ and Cu2+) into Cu nanoparticles, where their interplays realize improved optical properties and charge separation during photoreactions. Furthermore, the NH3-induced Cu nanoparticles could also serve as the adsorptive site for H+, thereby enabling 5629 μmol h-1 g-1 H2 generation over the optimum photocatalyst of Cu20/TiO2/Cu500. Such performance is associated to 35.44 and 1.71-fold improvements compared to pure TiO2 (Cu0/TiO2) and untreated Cu-ion modified TiO2 (Cu20/TiO2), respectively. This work offers a new synthetic strategy for obtaining photocatalyst with evenly distributed and highly accessible active sites, thus improving the commensurability of photocatalytic H2 generation from the industrial perspective.

Thiophene desulfurization: Effects of dendritic silica and PEG as surface modifier on ZnO photocatalyst

This work focused on desulfurizing thiophene using a photocatalyst comprising zinc oxide (ZnO) and fibrous silica nanospheres (KCC-1) to exploit the photocatalytic process. Six photocatalyst samples (commercial ZnO, KCC-1, ZnO/1.5KCC-1, ZnO/2.0KCC-1, ZnO/2.5KCC-1 and ZnO/PEG) were characterized using field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffractometry (XRD). It was found that the properties of ZnO were altered by incorporating KCC-1 to enhance the efficiency of thiophene desulfurization. Desulfurization performances were investigated using three parameters, which were initial pH, initial thiophene concentration, and photocatalyst loading. Each parameter was validated using thiophene desulfurization percentage and turbidity removal percentage. This work discovered that ZnO/2.0KCC-1 was the optimum photocatalyst with 83 % thiophene desulfurization. No clear trend was observed for turbidity removal percentage, yet the ZnO/KCC-1 photocatalyst was able to reduce turbidity significantly. The pH of the permeation rose from neutral to alkaline range due to the hydroxyl radicals (•OH) produced during the desulfurization process.

Construction of a BiOCl/Bi2O2CO3 S-Scheme Heterojunction Photocatalyst via Sharing [Bi2O2]2+ Slabs with Enhanced Photocatalytic H2O2 Production Performance.

The construction of a close contact interface is key to enhancing the photocatalytic activity in heterojunctions. In the work, the BiOCl/Bi2O2CO3 of sharing [Bi2O2]2+ slabs S-scheme heterojunction was prepared by a HCl in situ etching method. The optimal composite photocatalyst could accomplish sizable productivity of H2O2 to 2562.95 μmol g-1 h-1 under simulated solar irradiation, higher than that of primitive Bi2O2CO3 and BiOCl. Moreover, the synthesized catalysts showed good stability. The band structures of BiOCl and Bi2O2CO3 were determined, confirming the formation of BiOCl/Bi2O2CO3 S-scheme heterojunction The BiOCl/Bi2O2CO3, which obviously improved the separation efficiency of photoinduced carriers and effectively enhanced the redox ability of the photocatalyst. In addition, density functional theory (DFT) calculations were utilized to analyze the electron transfer properties and the constitution of the built-in electric field at the interface of BiOCl and Bi2O2CO3. The photocatalytic reaction process was further researched by electron paramagnetic resonance (EPR), indicating the active species in the photocatalytic production of hydrogen peroxide. Eventually, a feasible S-scheme electron transfer mechanism on the BiOCl/Bi2O2CO3 heterojunction during the photocatalytic H2O2 production process was proposed and discussed. This work provides a reliable strategy for the fine design of the S-scheme heterojunction.

Enhanced water decontamination via photogenerated electron delocalization of π → π* and D-π-A synergistically

Mixed-dimensional van der Waals heterojunctions (MD-vdWhs), known for exceptional electron transfer and charge separation capabilities, remain underexplored in photocatalysis. In this study, we leveraged the synergistic effect of intermolecular π → π* and D-π-A dual channels to fabricate novel MD-vdWhs. Owing to the synergistic effect, it exhibits superior electron transfer and delocalization ability, thereby enhancing its photocatalytic performance. The Optimal photocatalyst can degrade 98.78 % of 20 mg/L tetracycline (TC) within 15 min. Additionally, we introduced a novel proof strategy for investigating the photoelectron transfer path, creatively demonstrating the synergistic dual channels effect, which can be attributed to the carbonyl density and light-excitation degree. Notably, even under low-power light sources, it achieved complete inactivation of Escherichia coli within just 7 mins, far surpassing current cutting-edge research. This theoretical framework holds promise for broader applications within related studies.

Remarkable improvement in photocatalytic activity of g-C3N4 for NO oxidation through surface hydroxylation

The nitrogen oxide emissions originating from combustion pose significant risks to the environment. Photocatalysis is considered an efficient and environmentally friendly strategy to alleviate this problem. Graphitic carbon nitride (g-C3N4) is regarded as one of the most promising organic photocatalytic materials for environmental purification. However, its small specific surface area, weak adsorption and high recombination rate of charge carriers result in low intrinsic photocatalytic activity. To overcome these obstacles, a hydrothermal treatment of dicyandiamide-derived g-C3N4 (DCN) at different temperatures (140–200 °C) was employed to enhance the photocatalytic activity for NO oxidation. The experimental results demonstrated a significant improvement in the photocatalytic oxidation removal rate of NO after a hydrothermal treatment. The optimal photocatalyst, DCN-180, treated at 180 °C, demonstrated the highest NO removal efficiency (65.0 %), which is twice the value of pristine DCN (32.5 %). Additionally, the formation of the toxic intermediate NO2 was effectively suppressed during the reaction. Photoelectrochemical tests revealed that DCN-180 exhibited higher photocurrent density and smaller impedance radius compared to the untreated g-C3N4 sample. Moreover, density functional theory (DFT) calculations confirmed that the DCN-180 sample showed a stronger ability to adsorb O2 and NO. The enhanced photocatalytic NO oxidation performance of DCN-180 has been primarily attributed to its enlarged specific surface area (from 10.7 to 35.5 m2 g−1), local polarization effect, reduced interfacial charge transfer resistance, and improved adsorption abilities for NO and O2 molecules. This study provides valuable insights for designing and preparing highly efficient g-C3N4 based photocatalysts through surface modification for photocatalytic NO purification.

Rich Sulfur Vacancies and Reduced Schottky Barrier Height Synergistically Enable Au/ZnIn2S4 with Enhanced Photocatalytic CO2 Reduction into CO.

Constructing the plasmonic metal/semiconductor heterostructure with a suitable Schottky barrier height (SBH) and the sufficiently reliable active sites is of importance to achieve highly efficient and selective photocatalytic CO2 reduction into hydrocarbon fuels. Herein, we report Au/sulfur vacancy-rich ZnIn2S4 (Au/VSR-ZIS) hierarchical photocatalysts, fabricated via in situ photodepositing Au nanoparticles (NPs) onto the nanosheet self-assembled ZnIn2S4 (ZIS) micrometer flowers (MFs) with rich sulfur vacancies (VS). Density functional theory (DFT) calculations confirm that for the Au/VSR-ZIS system, the Au NPs serve as the reaction sites for H2O oxidation, and the VSR-ZIS MFs serve as those for CO2 reduction. The rich VS in the Au/VSR-ZIS hybrid can reduce its SBH so as to boost more hot electrons in the Au NPs across its Schottky barrier and then inject into the conduction band (CB) of the VSR-ZIS MFs. In addition, VS can also act as the electron sink to trap the photogenerated electrons, retarding the recombination of photogenerated carriers. The two merits effectively enhance the photogenerated electron density in the surface of VSR-ZIS MFs, availing CO2 photoreduction. In addition, the introduction of rich VS in the Au/VSR-ZIS hybrid can offer more active sites, benefiting the CO2 adsorption and accelerating the desorption of CO* from the surface of the photocatalyst. Therefore, under visible light illumination with no sacrificial reagent, the optimum photocatalyst (Au/VSR-ZIS-0.4) presents the enhanced and selective CO2 photoreduction into CO (8.15 μmol g-1h-1 and near 100%), which are superior to those of most of ZIS-based and plasmon-based photocatalysts. The photocatalytic activity is about 40.0-fold as high as that of the Vs-poor-ZIS (VSP-ZIS) MFs. This work contributes a viable strategy for designing highly efficient plasmonic photocatalysts by using the synergism of the anion vacancies and the optimized SBH induced by them.

NaSCN‐Induced Cyano‐Rich Porous Graphitic Carbon Nitride with Sodium Dopant and Nitrogen Vacancies for Enhanced Photosynthesis of Hydrogen Peroxide

AbstractDefect engineering has been considered as an efficient and facile tactics to optimize the bandgap structure and improve the oxygen adsorption ability of graphitic carbon nitride (g‐C3N4). Herein porous g‐C3N4 with nitrogen vacancies and sodium dopant as well as cyano (─C≡N) groups has been successfully constructed by direct pyrolysis of melamine in the presence of cyano‐rich sodium thiocyanate (NaSCN). Moreover, the incorporation of NaSCN is interestingly found to induce the relative high content of ─C≡N groups compared to other inorganic sodium compounds (NaCl, NaOH, and Na2SO4), which has been experimentally demonstrated to be beneficial for extending the light absorption range and promoting the efficient separation of photo‐generated electron–hole pairs as well as improving the oxygen adsorption ability. Benefiting from the above features, the optimal photocatalyst exhibits high H2O2 yield of 438.2 µm within 4 h and excellent cyclic stability.

Photocatalytic degradation of sulfamethazine using g-C3N4/TiO2 heterojunction photocatalyst: Performance, mechanism insight and degradation pathway

In the present research, Z-scheme g-C3N4/TiO2 heterojunction composite photocatalysts with varied g-C3N4 content were successfully prepared using the sol-gel technique combined with calcination methods. The morphology, crystallinity, chemical composition, and optical properties of the synthesized catalysts were characterized employing a series of techniques. Sulfamethazine (SMZ) was selected as the model pollutant to evaluate the photocatalytic activity of the prepared catalysts employing a 500 W xenon lamp as the light source to simulate sunlight. The results demonstrated that within 180 min of irradiation, 94.8 % of SMZ was removed by using the optimal photocatalyst (0.4CN/TiO2 composite sample), affording an apparent first-order rate coefficient of 0.0152 min−1 which was 3.8 or 2.0 times as much as that involving single g-C3N4 or TiO2 catalyst, respectively. The effects of catalyst dosage, initial pH, different water matrices, different substrates, and inorganic ions on the performance of 0.4CN/TiO2 photocatalyst were explored. Furthermore, the 0.4CN/TiO2 composite also displayed satisfactory cyclic stability. The results of radical quenching experiments revealed that the key active species in SMZ degradation were hydroxyl radicals (•OH), superoxide radicals (O2•−), and holes (h+). The efficient separation of photo-generated electrons and holes originating in the formation of a Z-scheme g-C3N4/TiO2 heterojunction was evidenced by photoluminescence and electrochemical impedance spectroscopy determination and should be responsible for the enhanced catalytic activity of the 0.4CN/TiO2 sample. In addition, the plausible pathways for the aqueous degradation of SMZ were suggested according to the identified degradation intermediates employing the HPLC/MS technique. In summary, the current research provides a novel insight into the development of Z-scheme heterojunctions in the realm of organic pollutant treatment.