Heterostructure Photocatalyst Research Articles

Plasmonic effect of metal nanoparticles on the photocatalytic properties of TiO2/rGO composite.

In this work, the plasmonic effect of Au and Ag nanoparticles in the heterostructure photocatalyst system (TiO2/rGO) was studied. The laser ablation approach was applied to synthesize Au and Ag nanoparticles to eliminate impurity influence in this plasmonic study. Characterizing tools such as SEM, TEM, XRD, Raman, UV-vis spectral techniques were applied to obtain morphological information and optical properties of the nanocomposites. Photocatalytic properties of ternary nanocomposities such as, TiO2/rGO/Ag and TiO2/rGO/Au, were evaluated against Methylene blue and Congo red dyes with changing concentration of plasmonic nanoparticles (Au and Ag) and it was founded that the nanocomposite with the concentration of 10-11 mol/L Au NPs in TiO2/rGO has the best photocatalytic activity. EIS study indicated that a significant decrease in resistance Rp (109 Ohms) was observed for TiO2/rGO at 10-11 mol/Lconcentration of Au and its lifetimes is 0.0118 s, supporting that TiO2/rGO/Au has the best photocatalytic activity at 10-11 mol/L Au in the TiO2/rGO nanocomposites.

Surface termination modulation for superior S-Scheme Bi2WO6/BiOI heterojunction photocatalyst: a hybrid density functional study

The prevailing theoretical frameworks indicate that depending on the growth conditions, the Bi2WO6(001) surface can manifest in three distinct terminations—DL-O–Bi (DL: double layers), O–Bi, and O–W. In this study, we conduct a comprehensive examination of the interplay between these terminations on Bi2WO6(001) and the 1I-terminated BiOI(001) facet, especially focusing on their impact on the photocatalytic activity of Bi2WO6/BiOI heterostructure, applying hybrid functional calculations. The models formulated for this research are designated as Bi2WO6(O–Bi)/BiOI(1I), Bi2WO6(DL-O–Bi)/BiOI(1I), and Bi2WO6(O–W)/BiOI(1I). Our findings reveal that Bi2WO6(O–Bi)/BiOI(1I) shows a type II band alignment, which facilitates the spatial separation of photo-generated electrons and holes. Notably, the Bi2WO6(DL-O–Bi)/BiOI(1I) configuration has the lowest binding energy and results in an S-scheme (or Step-scheme) heterostructure. In contrast to the type II heterostructure, this particular configuration demonstrates enhanced photocatalytic efficiency due to improved photo-generated carrier separation, augmented oxidation capability, and better visible-light absorption. Conversely, Bi2WO6(O–W)/BiOI(1I) presents a type I projected band structure, which is less conducive for the separation of photo-generated electron–hole pairs. In summation, this investigation points out that one could significantly refine the photocatalytic efficacy of not only Bi2WO6/BiOI but also other heterostructure photocatalysts by modulating the coupling of different terminations via precise crystal synthesis or growth conditions.

Highly visible-light-active sulfur and carbon co-doped TiO2 (SC-TiO2) heterogeneous photocatalysts prepared by underwater discharge plasma

To promptly and simply create highly crystalline S/C co-doped TiO2 (SC-TiO2) photocatalysts at room temperature and atmospheric pressure, we suggest a novel plasma-assisted sol-gel synthesis method. This method is a simultaneous synthetic process, in which an underwater plasma undergoes continuous reactions to generate high-energy atomic and molecular species that enable TiO2 to achieve crystallinity, a large surface area, and a heterogeneous structure within a few minutes. In particular, it was demonstrated that the heterogeneously structured TiO2 was formed by doping that sulfur and carbon replace O or Ti atoms in the TiO2 lattice depending on the composition of the synthesis solution during underwater plasma treatment. The resultant SC-TiO2 photocatalysts had narrowed bandgap energies and extended optical absorption scope into the visible range by inducing the intermediate states within bandgap due to generation of oxygen vacancies on the surface of TiO2 through synthesis, crystallization, and doping. Correspondingly, SC-TiO2 showed a significant degradation efficiency ([k] = 6.91 h−1) of tetracycline (TC, antibiotics) under solar light irradiation, up to approximately 4 times higher compared to commercial TiO2 ([k] = 1.68 h−1), resulting in great water purification. Therefore, we anticipate that this underwater discharge plasma system will prove to be an advantageous technique for producing heterostructural TiO2 photocatalysts with superior photocatalytic efficiency for environmental applications.

Insight into the highly efficient photocatalytic behavior of α-MoO3/AgBr heterojunction with S-scheme charge transfer strategy

The improvement of photoactivity and stability, as well as a deep insight into the intrinsic mechanism, has significant practical implications for heterostructured photocatalysts. Herein, AgBr nanoparticles were successfully anchored onto the surface of α-MoO3 nanostrips to form a 0D/2D AgBr/MoO3 heterojunction. The photocatalytic performance of the heterojunction under sunlight was enhanced about 9.5 times compared to primary α-MoO3, along with excellent stability. When exposed to various light sources, the photoexcited charge carriers in the heterojunction experienced different transfer pathways, and the relative contributions of the main reactive species to the photocatalysis were varied. The mechanism investigation reveals that the S-scheme transfer strategy of charge carriers as well as the internal electric field (IEF) at the α-MoO3/AgBr interface not only boosts their rapid spatial separation and transfer but maximizes the redox capacity, enhancing the photocatalytic activity of α-MoO3/AgBr and guaranteeing its stability.

Three-dimension TiO2@NiFe-layered double hydroxide core-shell heterostructures for enhanced photocatalytic phenol hydroxylation

One-step selectively photocatalytic phenol hydroxylation to produce Dihydroxybenzenes (DHB) is an attractive and challenging strategy. However, the rapid recombination of photogenerated carriers existed in single component photocatalyst seriously hinders the photocatalytic efficiency. The heterojunction strategy can optimize the band structure of the photocatalyst, and effectively improve the carriers' separation and transfer during the photocatalytic process. Herein, we successfully designed and prepared a 3D TiO2@Ni3Fe1-LDH core-shell heterostructure photocatalyst by coupling TiO2 nanorods with Ni3Fe1-LDH nanosheets for the photocatalytic phenol hydroxylation to produce DHB. The results showed that the 3D TiO2@Ni3Fe1-LDH core-shell heterostructure had a suitable energy band structure for the photocatalytic phenol hydroxylation and the heterostructure accelerated the carriers’ separation and transfer. Meanwhile, the high porosity and abundant active sites were conducive to the adsorption of H2O2 and the photogenerated carriers transfer efficiency from the photocatalyst to H2O2. The 3D TiO2@Ni3Fe1-LDH core-shell heterostructure showed excellent photocatalytic performance of phenol hydroxylation, where the phenol conversion was 48.6%, and the selectivity of DHB was 81.1% at 25 °C and 4 h of light illumination. Furthermore, the as-prepared photocatalysts exhibited good stability after four cycles of experiment. This work provided a convenient and efficient method for the green synthesis of DHB.

An indirect Z-scheme heterostructure of nano-gold layer immobilized Cu-Al-doped SrTiO3 and CoOx-WO3 for photocatalytic CO2 reduction

Perovskite oxides have emerged as promising photocatalysts for CO2 reduction to valuable chemicals and fuels. However, conventional perovskite oxide photocatalysts often suffer from inefficient charge separation and bulk charge recombination, negatively impacting overall photoactivity. In this work, we present a novel immobilized perovskite oxide-based photocatalyst sheet featuring an indirect Z-scheme heterostructure composed of Cu-loaded Al-doped SrTiO3 (Cu-ASTO) and CoOx-loaded WO3 (CoOx-WO3) with an ultrathin (20 nm) gold interlayer serving as a conductive bridge. We tested this photocatalyst sheet in a sealed reactor containing a CO2-saturated aqueous solution of 0.1 M NaHCO3 and a side window to allow irradiation. Under irradiation with a 300 W Xe lamp, the Cu-ASTO/Au/CoOx-WO3 immobilized photocatalyst sheet produced methane (CH4) at a rate of 2.676 µmol cm-2 h−1 and methanol (CH3OH) at 0.517 µmol cm-2 h−1. We attribute the superior activity of this catalyst to the all-solid-state indirect Z-scheme heterostructure that greatly extends the lifespan of photoinduced charge carriers and enhances the CO2 photoconversion reaction. In experiments conducted outside, we demonstrated the immobilized photocatalyst's performance under natural sunlight, producing CH4 at 0.307 µmol cm-2 h−1 and CH3OH at 0.069 µmol cm-2 h−1. This work provides design ideas for developing robust immobilized photocatalyst systems for the scalable operation of the CO2 photoreduction process and broadening the scope of applications for perovskite heterostructure photocatalysts.

Synergistic augmentation and rapid elimination of ciprofloxacin using a novel mesoporous nickel sulfide-adorned bismuth tungstate S-scheme heterojunction

Pharmaceutical contamination hazardously threatens the health of human beings and the ecological system. Heterogeneous photocatalysis provides a marvelous and effective strategy for directly breaking down these harmful contaminants during visible light exposure in the presence of a semiconducting photocatalyst. Even so, this approach is considerably challenged by inadequate photo-harvesting and swift recombination rates for photo-induced charge carriers of traditional photocatalysts. In this investigation, a novel NiS/Bi2WO6 step (S)-scheme heterostructure photocatalyst was constructed by surfactant-assisted sol-gel methodology and applied for ciprofloxacin (CIPF) oxidation beneath visible-light illumination. The Bi2WO6 catalyst was successfully decorated with diverse contents of NiS nanoparticles (NPs) to investigate their impact on the overall characteristics and catalytic performance of bismuth tungstate. The optimal photocatalyst, 9.0 wt% NiS/Bi2WO6, revealed astounding efficacy in CIPF elimination from water solution, with 100.0% degradation efficacy within 90-min visible light exposure. This novel photocatalyst achieved a degradation rate of ca. 0.966 μmol min−1, surpassing that attained employing bare Bi2WO6 by ∼8.0 times. Moreover, 9.0 wt% NiS/Bi2WO6 heterostructure has exhibited superior strength and stability with 98.0% sustainability. This outstanding improvement in photocatalytic proficiency and performance with high sustainability could be attributed to the enhanced transfer and separation rates of light-induced carriers occurring through the S-scheme route. This novel heterojunction design also enlarged the visible light-harvesting responsiveness. This study offers new insights into the design and building of promising S-scheme heterostructure photocatalytic systems for highly efficient solar conversion applications.

Visible-light induced ofloxacin photodegradation catalyzed by the S-scheme Bi2MoO6/NH2-MIL-68(In) heterojunction: Interfacial engineering, DFT calculations, and toxicity assessment

The construction of photocatalysts with high efficiencies for visible light utilization and rapid migration of photoinduced charge carriers is essential for efficient photodegradation of contaminants in water. Thus, a novel Bi2MoO6/NH2-MIL-68(In) S-scheme heterostructure photocatalyst was synthesized via a hydrothermal method. The ofloxacin photodegradation efficiency of optimized BMN-2 reached 100 % within 90 min of visible-light illumination. In addition, an S-scheme charge migration pathway was confirmed within BMN-2 based on work function calculations, in situ XPS, and ESR studies. The photocatalytic mechanism, potential intermediates, and four photodegradation pathways were proposed from theoretical calculations and experimental studies. In addition, h+, •O2–, and •OH were the predominant active species identified via scavenger experiments and ESR spectroscopy. Moreover, the comprehensive toxicity of the degraded OFL solution was lower than that of the initial solution, as indicated by QSAR predictions and E. colicultivation.

Construction of a novel metal-free heterostructure photocatalyst PRGO/TP-COF for enhanced photocatalytic CO2 reduction

The development of metal-free composite heterojunction catalysts is essential for economical and environmentally friendly carbon dioxide (CO2) conversion technologies. Most studies neglect the semiconductor property of graphene oxide (GO), which has the potential to participate in the construction of heterojunction catalysts. In this work, a novel organic-inorganic composite metal-free heterojunction photocatalyst was constructed for the photocatalytic CO2 reduction. Photo-reduced GO (PRGO) and sp2-carbon-chain triazine-based covalent organic framework (TP-COF) can be easily combined and form heterojunctions by a simple and green electrostatic self-assembly method through π-π interaction. The photogenerated electrons were transferred from the conduction band of PRGO to the valence band of TP-COF driven by energy band bending and built-in electric field, thus achieving effective charges separation. The strong reductive electrons on this S-scheme heterojunction efficiently and selectively reduced CO2 to CO. This work provides a new idea for designing GO-based heterojunction photocatalyst PRGO/TP-COF with potential application in CO2 photoreduction.

Facile synthesis of advanced BaTiO3/CuPbSbS3 heterostructure photocatalyst with enhanced piezo-photocatalytic degradation performance

The polarization electric field feature of piezoelectric materials is greatly beneficial to enhance the separation and migration of photogenerated carriers. Herein, we propose a BaTiO3/CuPbSbS3 (BTO/CPSS) heterostructure photocatalyst through the combination of hydrothermal and facile butyldithiocarbamate acid (BDCA) solution process, in which the catalytic degradation performance of BTO/CPSS can be effectively enhanced by the synergistic effect of piezoelectricity and semiconductor properties. Through dedicatedly adjusting the loading amount of CPSS, the Rhodamine B (RhB) degradation efficiency of BTO/CPSS achieves 9.33×10−2 min−1 along with a strong catalyst stability, which is attributed to the prolonged charge life time due to the piezoelectricity of the optimal BTO/CPSS. Moreover, the heterostructure of BTO/CPSS and polarization effect of BTO can further enhance the separation of electron-hole pairs, which can provide stronger driving force for catalytic degradation.

Probing charge transfer of NiCo2O4/g-C3N4 photocatalyst for hydrogen production

Quantum dots/two-dimensional (0D/2D) semiconductor photocatalysts demonstrate wide solar light absorption region and high charge transfer efficiency. However, the relation between the interfacial electric field and the charge transfer during the photocatalytic hydrogen production process is still unclear. Here, we construct NiCo2O4 quantum dots (QDs) and NiCo2O4 nanoparticles (NPs) anchored with 2D g-C3N4 (CN) to form NiCo2O4-QDs/CN and NiCo2O4-NPs/CN heterojunctions. The hydrogen production rate of CN loaded with NiCo2O4-QDs is about 3 times higher than that of CN loaded with NiCo2O4-nanoparticles. The electric field intensity at the NiCo2O4-QDs/CN interface is calculated to be about 15600 V cm−2, about 9 times higher than that of NiCo2O4-NPs/CN, which could effectively drive the electrons of CN to flow toward NiCo2O4 QDs, promoting photocarriers separation and hence greatly improving the photocatalytic performance. This work provides a method to understand the relationship between interfacial electric field strength and photogenerated charges of heterostructure photocatalysts.

Synthesis of Efficient S-Scheme Heterostructures Composed of BiPO4 and KNbO3 for Photocatalytic N2 Fixation and Water Purification.

The preparation of catalysts with heterojunction structures is a strategy to achieve efficient charge separation and high photocatalytic activity of photocatalysts. In this work, BiPO4/KNbO3 heterostructure photocatalysts were fabricated by a combination of hydrothermal and precipitation methods and subsequently employed in catalyzing N2-to-NH3 conversion and RhB degradation under light illumination. Morphological analysis revealed the effective dispersion of BiPO4 on KNbO3 nanocubes. Band structure analysis suggests that KNbO3 and BiPO4 exhibit suitable band potentials to form an S-scheme heterojunction. Under the joint action of the built-in electric field at the interface, energy band bending, and Coulomb attraction force, photogenerated electrons and holes with low redox performance are consumed, while those with high redox performance are effectively spatially separated. Consequently, the BiPO4/KNbO3 shows enhanced photocatalytic activity. The NH3 production rate of the optimal sample is 2.6 and 5.8 times higher than that of KNbO3 and BiPO4, respectively. The enhanced photoactivity of BiPO4/KNbO3 is also observed in the photocatalytic degradation of RhB. This study offers valuable insights for the design and preparation of S-scheme heterojunction photocatalysts.

G-C3N4@CPP/BiOClBr-OV biomimetic fractal heterojunction synergistically enhance carrier dynamics for boosted CO2 photoreduction activity

In recent years, there has been significant interest in generating high-value solar fuels via the photocatalytic reduction of CO2. Nonetheless, its large-scale application is impeded by low energy utilization efficiency and limited photocatalytic activity. This study employed carbonized pomelo peel (CPP), a waste biomass material, to successfully craft a CN@CPP/BOCB-OV ternary heterojunction abundant in N/O vacancy defects through secondary calcination and in-situ growth. The construction of the heterojunction and the emergence of defect-induced donor energy levels create a built-in interface electric field (IEF) and an interfacial electron transmission channel respectively, fortifying the separation and transport of photogenerated electrons. Crucially, following the incorporation of CPP, its distinctive 3D porous and heterojunction bionic flower structures expand the spectral absorption range. Acting as a superior electron acceptor, CPP reinforces the IEF, notably boosting carrier transport efficiency. Simultaneously, it operates as a hub for photothermal synergy and CO2 adsorption activation, achieving multi-site synergistic enhancement of photoreduction CO2 activity. Hence, the CN@CPP/BOCB-OV heterojunction demonstrates a substantial quantitative enhancement in CO2 photoreduction activity. Remarkably, it exhibits the capability to catalyze CO2 reduction even under infrared light excitation, which is of great significance for the cascade utilization of solar energy. Furthermore, employing DFT calculations, we elucidate the electron transfer mechanism at the heterojunction interface and outline potential pathways for photocatalytic CO2 reduction. The combination of waste biomass utilization, heterostructure construction and defect engineering provides a promising strategy for developing efficient heterostructure photocatalysts.

Decoration of Bi2MoO6 nanosheets with NH2-UiO-66 for boosting visible-light photocatalytic activities

Constructing heterostructured photocatalysts for organic contaminants elimination is promising in the area of environmental purification. For boosting the photocatalytic performance, modulating the heterojunction interface can enhance solar light utilization and facilitate the transporation of photoinduced charge carriers. In this research, octahedral NH2-UiO-66 nanoparticles with large surface area and wide light absorption range were prepared and further employed to in-situ construction of NH2-UiO-66/Bi2MoO6 nanocomposite. The optimized NH2-UiO-66/Bi2MoO6 nanocomposite displays enhanced photocatalytic activities in the elimination of rhodamine B (RhB) and tetracycline (TC). The corresponding degradation rate constant is about 4 and 1.76 times larger than that of individual Bi2MoO6. Combined with the photochemical and electrochemical results, it can be speculated that the higher photocatalytic performance is assigned to the accelerative photoinduced carrier transfer by the formation of well-contacted heterostructured interface. This study provides a theoretical basis for further developing organic–inorganic hybrid catalyst with significant improvement of photocatalytic properties in wastewater treatment.

Transition metals-doped g-C3N4 nanostructures as advanced photocatalysts for energy and environmental applications

Graphitic carbon nitride (g–C3N4)–based heterostructured photocatalysts have received significant attention for its potential applications in the treatment of wastewater and hydrogen evolution. The utilization of semiconductor materials in heterogeneous photocatalysis has recently received great attention due to their potential and eco-friendly properties. Doping with metal ions plays a crucial role in altering the photochemical characteristics of g-C3N4, effectively enhancing photoabsorption into the visible range and thus improving the photocatalytic performance of doped photocatalysts. As an emerging nanomaterial, nanostructured g-C3N4 represents a visible light-active semiconducting photocatalyst that has attracted significant interest in the photocatalysis field, particularly for its practical water treatment applications. To the best of our knowledge, investigations of functionalized photocatalytic (PC) materials on 3d transition metal-doped g-C3N4 remain unexplored in the existing literature. g-C3N4 based heterohybrid photocatalysts have demonstrated excellent reusability, making them highly promising for wastewater treatment applications. This paper describes the overview of numerous studies conducted on the heterostructured g-C3N4 photocatalysts with various 3d metals. Research studies have revealed that the introduction of element doping with various 3d transition metals (e.g., Ti, Mn, Fe, Co, Ni, Cu, Zn, etc.) into g-C3N4 is an efficient approach to enhance degradation efficacy and boost photocatalytic activity (PCA) of doped g-C3N4 catalysts. Moreover, the significance of g-C3N4 heterostructured nanohybrids is highlighted, particularly in the context of wastewater treatment applications. The study concludes by providing insights into future perspectives in this developing area of research, with a specific focus on the degradation of various organic contaminants.

High-performance photocatalytic reduction of Cr(VI) using a retrievable Fe-doped WO3/SiO2 heterostructure

The enhancement of the photocatalytic performance of pristine WO3 was systematically adjusted due to its fast recombination rate and low reduction potential. A designed heterostructure photocatalyst was necessarily synthesised by Fe3+ metal ions doping into WO3 structure with and composition modification. In this study, we synthesised a retrievable Fe-doped WO3/SiO2 heterostructure using a surfactant-assisted hydrothermal method. This heterostructure was then employed as an effective photocatalyst for the removal of Cr(VI) under visible light irradiation. Enlarged photocatalytic reduction was observed over a synergetic 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite, resulting in dramatically increased activity compared with undoped WO3 and SiO2 nanomaterials under visible light illumination within 90 min. The presence of 7.5 mol% Fe3+ ion dopant in WO3 optimised electron–hole recombination, consequently reducing WO3 photocorrosion. After adding SiO2 nanoparticles, the binary WO3-SiO2 nanocomposite played roles as both adsorbent and photocatalyst to increase specific surface area. Thus, the 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite catalyst had more active sites on the surface of catalyst, and enhanced photocatalytic reduction was significantly achieved. The results showed 91.1% photocatalytic reduction over the optimum photocatalyst, with a photoreduction kinetic rate of 21.1 × 10–3 min−1, which was approximately four times faster than pristine WO3. Therefore, the superior optimal photocatalyst demonstrated reusability, with activities decreasing by only 9.8% after five cycles. The high photocatalytic performance and excellent stability of our photocatalyst indicate great potential for water pollution treatments.

Fabrication of MoSe2/Bi3O4Br Z-scheme heterojunction with enhanced photocatalytic performance

Exploring a Z-scheme heterojunction photocatalyst with efficient charge separation and outstanding redox ability is necessary but very challenging. MoSe2 has received much attention as a co-catalyst due to its excellent optical properties. Herein, First-principles density functional theory (DFT) was employed for theoretical calculations of the energy band structure of Bi3O4Br, revealing crossed energy band structures with MoSe2, indicating favorable conditions for heterojunction formation. A solvothermal method was then used to synthesize MoSe2/Bi3O4Br heterostructure photocatalysts with a 2D/2D layered configuration. Characterization via SEM, TEM, DRS, XPS, BET, EIS, and PL confirmed that the MoSe2/Bi3O4Br heterostructure exhibited a larger specific surface area, more active sites, lower impedance, and reduced carrier recombination rate compared to pure Bi3O4Br and MoSe2. These features are advantageous for photocatalytic reactions. The optimized 2.5% MoSe2/Bi3O4Br photocatalyst demonstrated superior performance, achieving nearly 100% photodegradation of RhB under 90 min of simulated sunlight, with an apparent rate constant k value 7.57 times higher than that of Bi3O4Br. The composite photocatalyst exhibited excellent cycling stability over five experiments without significant reactivity attenuation. Finally, a plausible Z-scheme photocatalytic mechanism for MoSe2/Bi3O4Br heterojunctions is proposed based on experimental findings. This study provides new insights for exploring the construction of wide-band semiconductor heterojunctions.

Boosted photocatalytic accomplishment of 3D/2D hierarchical structured Bi4O5I2/g-C3N4 p-n type direct Z-scheme heterojunction towards synchronous elimination of Cr(VI) and tetracycline

The threats posed by heavy metal ions and antibiotics present in natural aqueous environments have been a serious cause of concern across the globe. The synchronous elimination of these contaminants through visible light responsive semiconductor mediated photocatalysis is a suitable strategy to solve this problem. However, designing proficient photocatalysts for the said purpose is a crucial task. Herein, hierarchical 3D/2D architectures of Bi4O5I2/g-C3N4 p-n type direct Z-scheme heterojunction photocatalysts (BOCNs) were fabricated by a two-step solvothermal-calcination approach. The characterisation of BOCNs by XRD, FTIR, XPS, SEM, TEM, HRTEM, LSV and MS techniques corroborated the robust heterojunction formation between Bi4O5I2 and g-C3N4. The presence of g-C3N4 and application of high treatment temperature (400 °C) assisted the formation of BiOC bond which is responsible for the development of an intimate interfacial interaction in BOCN. The heterostructured photocatalyst (BOCN3) demonstrated higher rate constant (kCr(VI)/synchronous) of 0.068 min−1 for Cr(VI) detoxification and that (kTCH/synchronous) of 0.075 min−1 for TCH degradation synchronously with respect to the reported values. The determined rate constants are about 1.8 folds greater than those were observed in isolated systems. The expedited photocatalytic activity can be ascribed to its wide visible light response, minimum charge recombination rate and increased redox ability. These are resulted from the synergistic effect of hierarchical 3D/2D architecture construction, existence of strong BiOC interfacial bond, p-n heterojunction formation and prevalence of direct Z-scheme charge transfer principle. The synchronous elimination of Cr(VI) and TCH over BOCN3 up to the fifth consecutive cycle without any appreciable change in photoactivity signified its enhanced stability and reusability. The plausible mechanism for the spectacular photocatalytic performance of BOCN3 was proposed.

Novel Cerium (IV) Oxide -Ti3C2- titanium dioxide heterostructure photocatalyst for pharmaceutical pollutants removal: Photocatalyst characterization, process optimization and transformation pathways

Tetracycline (TC) is a widely applied antibiotic recognized for its potential negative consequences on human health and ecological balance. In this study, a novel photocatalyst, Cerium (IV) oxide -Ti3C2- titanium dioxide (CeMXT), was synthesized through sonochemical and impregnation techniques, subsequently subjected to comprehensive characterization employing diverse methods including XRD, SEM, TEM, HR-TEM, Raman, XPS, and BET. The optimization of TC degradation was pursued using the Response Surface Methodology (RSM), encompassing variables such as initial TC concentration, irradiation duration, photocatalyst dosage, and pH. The degradation efficacy was investigated through free radical trapping experiments, revealing the pivotal roles of OH and superoxide anion radicals. Remarkable degradation efficiency, reaching 94.70 %, was achieved under specific parameter conditions: 22.19 mg/L TC concentration, 104.13 min irradiation, 0.65 g/L photocatalyst dosage, and pH 4.72. This exceptional performance could be attributed to the elevated generation of oxidant species facilitated by the Z-scheme electron transfer heterojunction. Furthermore, LC-Mass analysis was employed to delineate the intermediates formed during TC photodegradation, culminating in proposing a conceivable degradation pathway. The impressive proficiency of the CeMXT photocatalyst underscores its potential application for effective large-scale treatment of persistent organic pollutants in wastewater treatment facilities. Additionally, comparative analysis with a recently developed photocatalyst highlights its promise as a viable alternative for the remediation of such contaminants in aquatic ecosystems.

Enhanced charge carriers separation/transportation via S-scheme ZnCeS–ZnWO heterostructure nanocomposite for photodegradation of synthetic dyes under sunlight

Domestic wastage and liquid discharge from industries cause serious water pollution and severely damage the life cycle of living species. Therefore, it is necessary to construct efficient photocatalysts for the removal of toxic pollutants from water. Herein, a novel heterostructure ZnWO–ZnCeS nanocomposite was prepared by the sol-gel route and studied its physical and photocatalytic properties using various analytical techniques. Under sunlight irradiation, the ZnWO–ZnCeS photocatalyst eliminated 99.7, 99.1, 99.0 % rhodamine-B (RhB), methylene blue (MB), and safranin-O (SO) dyes within 70 min with excellent performance higher than individual ZnWO and ZnCeS catalysts. The optimization tests exhibit the catalyst loading = 30 mg, dye content = 25 ppm, solution pH = 8 of ZnWO–ZnCeS against MB dye for practical application. The heterojunction of coupled ZnWO and ZnCeS leads to a synergistic effect that facilitates the charge transport and hampers the recombination of photo-induced charge carriers thereby leading to boosted photocatalytic performance. Furthermore, based on the scavenging test, the hydroxyl and superoxide radicals were the reactive species during the photodegradation reaction. The designed photodegradation reaction mechanism has proposed the formation of an S-scheme in ZnWO–ZnCeS that led to the accumulation of electrons at ZnCeS and holes at ZnWO, favoring the formation of reactive species for dye degradation. Moreover, this work provides a novel direction to synthesize S-scheme heterostructure photocatalysts for application in wastewater treatment.