High Charge Separation Efficiency Research Articles

In-situ one-step construction of poly(heptazine imide)/poly(triazine imide) heterojunctions for photocatalytic hydrogen evolution.

The construction of heterojunctions is challenging, requiring atomic-level contact and interface matching. Here, we have achieved atomic-level interfacial matching by constructing poly(heptazine imide)/poly(triazine imide) crystalline carbon nitride heterojunctions in an in-situ one-step method. The content of poly(triazine imide) in heterojunctions is positively related to the proportion of lithium chloride in potassium chloride and lithium chloride mixed-salts. The optimized heterojunction achieves an apparent quantum efficiency of 48.34 % for photocatalytic hydrogen production at 420 nm, which is at a good level in polymeric carbon nitride photocatalysts. The proposed ion-thermal assisted heterojunction construction strategy contributes to the development of polymeric carbon nitride photocatalysts with high crystallization and high charge separation efficiency.

Hydrogel Enabled Dual‐Shielding Improves Efficiency and Stability of BiVO4 Based Photoanode for Solar Water Splitting

AbstractPhotoelectrochemical solar to hydrogen conversion is a promising approach to solve energy and environmental problems. One of the paramount challenges to overcome is to achieve high solar to hydrogen efficiency while retaining stable service behavior without photocorrosion of the photoanode. In this study, a hydrogel‐enabled dual‐shielding (FeCoOx/PAAM) strategy is reported to improve efficiency and suppress photocorrosion of photoanode during solar water splitting especially in a high‐intensity illumination. Anodic photocorrosion of BiVO4 photoanodes involves the chemical and physical construction changes under the conditions of light field, electric field, and electrolyte. The utilization of FeCoOx/PAAM on BiVO4 inhibits the improvement of oxygen evolution reaction kinetics, bubble dynamics, and blocking ion dissolution diffusion, which effectively suppresses anodic photocorrosion and simultaneously improves efficiency of BiVO4 photoanode. The improved BiVO4/FeCoOx/PAAM photoanode shows a superior photocurrent density of 19.88 mA cm−2 at 1.23 V versus RHE, and a high charge separation efficiency of 98% with enhanced stability over 60 h (300 mW cm−2). This study contributes to developing a universal method of photoanode protection to anti‐photocorrosion, facilitating the development of high‐efficiency, high‐stability, and pollution‐free hydrogen production.

A Solar and Seawater Co‐Involved Durable Rechargeable Battery Enabled by Crown Ether‐Rich Polymer‐Mediated Photoelectrodes

AbstractThe first flow‐type solar and seawater co‐mediated sodium‐air rechargeable battery (SSRB) for efficient solar‐to‐electrochemical energy conversion/storage is established. Such SSRB is enabled by a robust self‐regulated CEP/ZnWO4/WO3 heterojunction photoelectrochemical electrodes (PE) by passivating predesigned crown ether‐rich photoresponsive covalent organic polymer (CEP) layers onto ZnWO4‐modified WO3 nanosheet arrays. The PE design utilizes the previously‐unexplored self‐mediated effect of CEP to endow PE with superior stability, facilitated electrode reaction kinetics, and high efficiency of spatial charge separation simultaneously. This leads to remarkable light‐enhanced oxygen evolution catalysis with impressive photocurrent density up to 6.1 mA cm−2 at 1.23 V versus RHE in seawater – surpassing metal‐oxide‐based PEs ever reported for seawater splitting. Thus, the SSRB breaks the limit of the equilibrium voltage (3.47 V) of conventional seawater sodium‐air cells to deliver a low charge voltage of 2.71 V along with stable photo‐charge over 100 h and good photo‐charge/normal discharge cycling stability over 240 h – superior to almost all existing light‐involved air batteries. Combined experimental and modeling studies for the first time unveil the multi‐regulation effects of CEP passivation which prevents detrimental Cl‐corrosion, and promote oxygen evolution kinetics.

Two birds with one stone: Facile fabrication of a ternary ZnIn2S4/BiVO4/MWCNTs nanocomposite for photocatalytic detoxification of priority organic pollutants and hydrogen production with a proposed mechanism

A series of ternary nanocomposites with different weight percentages of zinc indium sulfide, bismuth vanadate, and multiwalled carbon nanotubes (ZnIn2S4/BiVO4/MWCNTs) were synthesized using a simple thermal impregnation method to obtain high charge separation and transfer efficiency, thus improving their photocatalytic performance. The 20 wt% ZnIn2S4/BiVO4/MWCNTs (20 wt% ZBM) nanocomposite exhibited enhanced photocatalytic activity compared to pure BiVO4 and ZnIn2S4 for the degradation of methylene blue, acetaminophen, and allopurinol in an aqueous solution when exposed to a visible light source and atmospheric oxygen. This nanocomposite demonstrated a particularly high degradation rate constant (k = 6.39 × 10−2 min−1) for the photocatalytic degradation of methylene blue. The introduction of MWCNTs boosted the photocatalytic performance of the 20 wt% ZBM nanocomposite, attaining a maximum H2 production of 1704 μmol g−1. Repeated photocatalytic H2 generation reached 1621 μmol g−1 after 5 h of irradiation with four consecutive cycles. Therefore, we propose a “two birds with one stone” strategy for greatly improved photocatalytic wastewater detoxification and H2 production by prolonging the lifetime of the photogenerated electron–hole pair separation.

In situ synthesis of graphitic carbon nitride nanosheet/Ti3C2Tx MXene/TiO2 Z-scheme heterojunctions boosting charge transfer for full-spectrum driven photocatalytic sterilization

The development of a full-spectrum responsive photocatalytic germicide with excellent charge separation efficiency to harvest high antimicrobial efficacy is a key goal yet a challenging conundrum. Herein, graphitic carbon nitride nanosheet (PCNS)/Ti3C2Tx MXene/TiO2 (PMT) Z-scheme heterojunctions with robust interface contact were crafted by in situ interfacial engineering. The strong internal electrical field (IEF) from PCNS to TiO2, evinced by the Kelvin Probe Force Microscopy (KPFM) characterization, can obtain high charge separation efficiency with 73.99%, compared to Schottky junction PCNS/Ti3C2Tx (PM, 32.88%) and PCNS (17.70%). The Ti3C2Tx component can not only serve as a transfer pathway to accelerate the recombination of photoexcited electrons of TiO2 and holes of PCNS under the Ultraviolet–visible (UV–vis) light irradiation, but also replenish the photogenic electron concentrations to semiconductors in the near-infrared (NIR) light illumination. Meanwhile, the increased temperature due to the localized surface plasmon resonance (LSPR) can further boost the electronic activity to the generation of reactive oxygen species (ROS). Taken together, the PMT performs a high disinfection efficiency up to 99.40% under full solar spectrum illumination, 3.88 and 9.75 times higher than PCNS and TiO2, respectively, surpassing many reported Z-scheme heterojunctions. This work offers guidance for the design of Z-scheme heterojunction with the implanting of plasmons to secure excellent full-spectrum responsive photocatalytic sterilization performance.

Dimension dependent photocatalysis over Znln2S4: Controllable synthesis and catalytic mechanism insight

Dimensional control of nano-photocatalysts enables the enhancement of catalytic activity through optimization of electronic structures. In this study, we take Znln2S4 as an example to demonstrate the influence of dimensional structure on photocatalytic reactions. Firstly, we successfully prepared three different dimensional structures of Znln2S4 (including 1D, 2D, and 3D Znln2S4) using a surfactant-assisted synthesis method. In photocatalytic experiments, we found that Znln2S4 exhibits dimension-dependent catalytic performance in both photocatalytic hydrogen production and photodegradation of dye solutions. Among them, 2D ZnIn2S4 demonstrates highest photocatalytic performance. The hydrogen evolution rate of 2D ZnIn2S4 reached 0.69 mmol g−1 h−1, which was 3.29 and 1.17 times higher than 1D ZnIn2S4 and 3D ZnIn2S4, respectively. In addition, the degradation rate of Rodamine B (RhB) by 2D ZnIn2S4 reached 92.3 % within 30 min, significantly higher than that of 1D ZnIn2S4 (70.3 %) and 3D ZnIn2S4 (86.3 %). The origin for high activity of 2D ZnIn2S4 was investigated by multiple perspectives including light absorption range, charge separation efficiency, band structure, and specific surface area. The results revealed that the high activity of 2D ZnIn2S4 may mainly originate from its dimension-controlled high charge separation efficiency.

Reversible modulation of interlayer stacking in 2D copper-organic frameworks for tailoring porosity and photocatalytic activity

The properties of two-dimensional covalent organic frameworks (2D COFs), including porosity, catalytic activity as well as electronic and optical properties, are greatly affected by their interlayer stacking structures. However, the precise control of their interlayer stacking mode, especially in a reversible fashion, is a long-standing and challenging pursuit. Herein, we prepare three 2D copper-organic frameworks, namely JNM-n (n = 7, 8, and 9). Interestingly, the reversible interlayer sliding between eclipsed AA stacking (i.e., JNM-7-AA and JNM-8-AA) and staggered ABC stacking (i.e., JNM-7-ABC and JNM-8-ABC) can be achieved through environmental stimulation, which endows reversible encapsulation and release of lipase. Importantly, JNM-7-AA and JNM-8-AA exhibit a broader light absorption range, higher charge-separation efficiency, and higher photocatalytic activity for sensitizing O2 to 1O2 and O2•− than their ABC stacking isostructures. Consequently, JNM-8-AA deliver significantly enhanced photocatalytic activities for oxidative cross-coupling reactions compared to JNM-8-ABC and other reported homogeneous and heterogeneous catalysts.

An MgO passivation layer and hydrotalcite derived spinel Co2AlO4 synergically promote photoelectrochemical water oxidation conducted using BiVO4-based photoanodes.

MxCo3-xO4 co-catalysed photoanodes with high potential for improvement in PEC water-oxidizing properties are reported. However, it is difficult to control the recombination of photogenerated carriers at the interface between the catalyst and cocatalyst. Here, an ultra-thin MgO passivation layer was introduced into the MxCo3-xO4/BiVO4 coupling system to construct a ternary composite photoanode Co2AlO4/MgO/BiVO4. The photocurrent density of the electrode is 3.52 mA cm-2, which is 3.2 times that of BiVO4 (at 1.23 V vs. RHE). The photocurrent is practically increased by 0.86 mA cm-2 and 1.56 mA cm-2 in comparison with that of Co2AlO4/BiVO4 and MgO/BiVO4 electrodes, respectively. Meanwhile, the Co2AlO4/MgO/BiVO4 electrode has the highest charge separation efficiency, the lowest charge transfer resistance (Rct) and best stability. The excellent PEC performance could be attributed to the inhibitive effect provided by the MgO passivation layer that efficaciously suppresses the electron-hole recombination at the interface and drives the hole transfer outward, which is induced by Co2AlO4 to capture the electrode/electrolyte interface for efficient water oxidation reaction. In order to understand the origin of this improvement, first-principles calculations with density functional theory (DFT) were performed. The theoretical investigation converges to our experimental results. This work proposes a novel idea for restraining the recombination of photogenerated carriers between interfaces and the rational design of efficient photoanodes.

Enhanced visible light photocatalytic activity of octopod Ag3PO4 microcrystals with high index crystal faces.

Novel octopod shaped Ag3PO4 microcrystals were successfully fabricated by a simple ion exchange method under the conditions of a hot water bath using [Ag(NH3)2]+ solution and Na2HPO4 solution as the precursors. Meanwhile, sphere and cube shaped Ag3PO4 microcrystals were also prepared followed by changing reaction materials as well as temperature. The surface morphology, microstructure and photocatalytic performance were investigated on the three different shaped crystals respectively. Compared to sphere and cube counterparts, the obtained octopod shaped Ag3PO4 crystals possess 8 symmetric feet with sharp tips and exhibit higher photocatalytic activity and better cycle stability. After further exploring its formation process, UV-vis diffusion reflectance properties as well as photocurrent transient response, it was found that the Ag3PO4 octopod had exposed high index crystal faces, and possessed a narrow band gap as well as high photoexcited transient charge separation efficiency. The results show that the improved photocatalytic activity of octopod shaped Ag3PO4 is mainly due to the synergistic action of the strong light absorption capacity and high carrier separation efficiency. These results highlight the tremendous practical application of octopod Ag3PO4 microcrystals in visible light photocatalysis.

Selective cellobiose photoreforming for simultaneous gluconic acid and syngas production in acidic conditions

Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of •O2− during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (∼56 μmol g−1 h−1) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.

(Invited) Correlation of Exciton and Charge Carrier Dynamics with the Performance of Metal Halide Perovskite Solar Cells

Perovskite solar cells have been recognized as a newly emerging solar cell with the potential of achieving high efficiency with a low cost fabrication process. In particular, facile solution processed cell fabrication facilitated rapid development of optimum cell structure and composition. Over the last few years, the cell efficiency has exceeded 25%.Highly efficient charge transfer reactions in addition to high charge separation efficiency and swift charge transport with minimum charge recombination are required to improve solar cell performance. Intensive studies have been focused on monitoring photo-induced exciton formation and charge dissociation, charge transport and interfacial charge transfer dynamics including interfacial charge recombination in perovskite solar cells.[1-5] Several parameters have been identified to influence these charge carrier dynamics, and therefore the solar cell performance.[1-5] Clarifying these parameters is extremely important to understand the charge transfer mechanisms to further improve solar cell performance.In this presentation, we will present parameters controlling charge dissociation in metal halide perovskites and their charge separation and recombination dynamics at the perovskite interfaces employing a series of transient absorption and emission spectroscopies. Correlation of the key parameters controlling the exciton and charge carrier dynamics with the solar cell performance will be discussed [1-5].This work was partly supported by JSPS KAKENHI Grant (19H02813) and (22H02182), and the Collaborative Research Program of Institute for Chemical Research, Kyoto University (grant number 2023-45 and 2022-99), Japan. We would like to acknowledge supports from the Australia-Japan Foundation for the international collaborative project. We also acknowledge supports from ARC LIEF fund (LE200100051 and LE170100235), Australia and School of Engineering in RMIT University, and Forefront Research Center, Faculty of Science at Osaka University.

In Situ Synthesis of Bi2S3/BiFeO3 Nanoflower Hybrid Photocatalyst for Enhanced Photocatalytic Degradation of Organic Pollutants.

Photocatalytic degradation of Malachite Green oxalate (MG) in a water body is of significant importance to our health protection, as it could cause various serious diseases. However the photocatalytic activity of most catalysts is still unsatisfactory, due to the poor reactive oxygen species production as a result of sluggish charge separation. Here, innovative nanoflower-shaped Bi2S3/BiFeO3 heterojunctions are prepared via a facile sol-gel method, exhibiting an enhanced reactive oxygen species generation, which leads to the excellent photocatalytic performance toward MG degradation. We verify that interfacing BiFeO3 with Bi2S3 could form a fine junction and offers a built-in field to speed up charge separation at the junction area; as a result, this shows much higher charge separation efficiency. By virtue of the aforementioned advantages, the as-prepared Bi2S3/BiFeO3 heterojunctions exhibit excellent photocatalytic performance toward MG degradation, where more than 99% of MG is removed within 2 h of photocatalysis. The innovative design of nanoflower-like Bi2S3/BiFeO3 heterojunctions may offer new viewpoints in designing highly efficient photocatalysts for environmentally related applications.

Low-temperature plasma-induced porous Sb2WO6 microspheres with rich oxygen vacancies to promote high-performance photocatalytic activity

The escalating issue of water pollution has sparked significant attention among researchers in the field of photocatalysis. Consequently, it holds immense significance to develop photocatalysts that exhibit high charge separation efficiency and stability for effectively degrading pollutants in water. In this study, OV-Sb2WO6-X photocatalyst was synthesized by incorporating oxygen vacancies into pristine Sb2WO6. The introduction of oxygen vacancies significantly enhanced the charge separation efficiency, resulting in a substantial improvement in the photocatalytic activity. The content of oxygen vacancies was controlled by plasma treatment time, processed for 10, 20 and 30 min, and electron paramagnetic resonance (EPR) test demonstrated the introduction of oxygen vacancies successfully. Furthermore, X-ray photoelectron spectroscopy (XPS) characterized the internal electron flow direction of the photocatalyst. OV-Sb2WO6-20 showed the degradation rate of Rhodamine B (RhB) that nine times of the Sb2WO6, while the Tetracyclines (TC) degradation rate showed 3.5 times that of Sb2WO6. Moreover, OV-Sb2WO6-20 exhibited superior stability in terms of recycling activity and material structural integrity. Additionally, free radical trapping experiments and electron spin-resonance spectroscopy characterization demonstrated that h+ played a crucial role as the reactive species during the degradation process. This research presents a viable approach for the modification of Sb2WO6-based materials, enabling effective treatment of dye wastewater and achieving successful purification.

A ternary rh/c-In2O3/CdIn2S4 heterostructure photocatalyst: In-situ construction and boosting high-efficient visible-light H2 production

Narrow band gap semiconductors have attracted more attention in photocatalytic. It is still a challenge to design heterojunction photocatalysts with efficient visible-light-harvesting and high redox ability water splitting hydrogen fuel production. Herein, a ternary heterojunction of rhombic phase In2O3 (rh-In2O3)/cubic phases In2O3 (c-In2O3) homojunction combined CdIn2S4 (rh/c-IO/CIS) was designed and constructed via in-situ pyrolysis of a liquid precursor. The as-synthesized rh/c-IO/CIS heterojunction exhibits a nanoplate structure composed of multilayers of tightly coupled ultrathin flakelets. The nanoflakelets stacking structure endows abundant exposed active sites and efficient visible-light-harvesting. Experimental results show rh/c-IO/CIS heterojunction follows a S-scheme mechanism proving high charge separation efficiency and strong redox capability. Thus, the catalyst exhibits excellent photocatalytic hydrogen production performance. The hydrogen evolution rate can get 4.7 mmol·g−1·h−1, it is 3.6 folds and 7.8 folds higher than that of CdIn2S4 and rh/c-In2O3. This work provides a new tack for rational design and fabrication of photocatalysts with enhanced photocatalytic hydrogen energy production performance.

Construction of interfacial electric field via Bimetallic Mo2Ti2C3 QDs/g-C3N4 heterojunction achieves efficient photocatalytic hydrogen evolution

Exploiting photocatalysts with high interfacial charge separation efficiency remains a huge challenge for converting solar energy into chemical energy. Herein, a novel 0D/2D heterojunction is successfully constructed by using bimetallic Mo2Ti2C3 MXene Quantum Dots (Mo2Ti2C3 QDs) firmly immobilized on the surface of g-C3N4 nanosheet via an electrostatic self-assembly strategy. The Mo2Ti2C3 QDs/g-C3N4 exhibits an efficient and stable photocatalytic hydrogen production performance up to 2809 µmol g-1h−1, which is 7.96 times higher than pure g-C3N4 nanosheet, and prominently exceeding many reported photocatalysts. Besides, a prominent apparent quantum yield achieves 3.8% at 420 nm. The significant performance improvement derives from the giant interfacial electric field that formed between large interface contact areas, ensuring greatly efficient separation and transfer of the photogenerated carriers. Furthermore, the 0D/2D heterojunction possesses high-quality interfacial contact, which reduces the interfacial recombination of photoinduced electrons and holes, causing the quick electron transfer from the g-C3N4 to electron acceptor Mo2Ti2C3 QDs, thus enhancing the charge utilization. Kelvin probe force microscopy (KPFM) measurements and density functional theory (DFT) calculation comprehensively demonstrate that g-C3N4 modified by Mo2Ti2C3 QDs can modulate the electronic structure and prompt the establishment of the interfacial electric field, which consequently leads to efficient photocatalytic activity. This study adequately illustrates that constructing heterojunction interfacial electric fields based on MXene quantum dots is a prospective pathway to engineering high-performance photocatalytic platforms for solar energy conversion.

Bridging Effect of Carbon Nitride with More Negative Conduction Potential and Halogens Promotes the Liquid-Phase Oxidation of Aromatic C-H Bonds.

The selective oxidation of benzyl C-H bonds of alkyl aromatic hydrocarbons under solvent-free conditions by using heterogeneous catalysis is a challenging task. In this work, we designed a carbon nitride photocatalyst with a high charge separation efficiency and a directed charge transfer path, which was doped with Ni and Br in the carbon nitride skeleton. Br was deposited directionally onto the electron-rich Ni surface traps to form a bond with Ni, which acted as a charge transfer bridge connecting CN and Br, resulting in a bridging effect. Photogenerated electrons were transferred from Ni target to Br, and electrons were aggregated to form a directional charge transfer path, thereby enhancing the photocatalytic performance of CN. The photocatalyst was utilized for the selective oxidation of ethylbenzene at room temperature, atmospheric pressure, and solvent-free conditions. Under batch conditions simulating solar irradiation, the conversion of ethylbenzene was 43.3% and the selectivity of the product acetophenone was up to 92.0%. With the continuous flow strategy, the conversion of ethylbenzene was increased to 52.4 and 48.1%, respectively, while the selectivity reached 92.7 and 91.0%, and the reaction time was reduced from 24 to 2.1 h. The catalyst was also found to be broadly applicable for the selective oxidation of C-H bonds in the benzyl position of alkyl aromatic hydrocarbons.

Piezoelectric effect achieves efficient carriers’ spatial separation and enhanced photocatalytic H2 evolution of UiO-66-NH2@CdS by transforming charge transfer mechanism

The internal electric field induced by piezoelectric effect can optimize the transport pathway of photogenerated charge in photocatalysis. We constructed an effcient piezoelectric photocatalytic heterojunction UiO-66-NH2@CdS and achieved a shift in the charge transfer mechanism through the piezoelectric effect, resulting in excellent photocatalytic H2 evolution performance. The optimal heterojunction under the ultrasonic environment exhibited 2028.48 μmol·g−1·h−1 photocatalytic H2 evolution performance, roughly four times better than no-ultrasound condition. Because of the piezoelectric polarization of UiO-66-NH2, the photogenerated carrier transport mechanism was changed from type Ⅱ to the more favorable Z-scheme for charge separation. Meanwhile, the built-in electric field caused by the piezoelectric effect can act as a powerful driving force for charge separation, achieving high charge separation efficiency and promoting the utilization of photogenerated electrons. This work would provide a fresh perspective for MOF-based piezoelectric photocatalysts and have implications for the design of efficient Z-scheme heterojunctions.

Development of bismuth-rich bismuth oxyhalides based photocatalyst for degradation of a representative antibiotic under simulated solar light irradiation

In this study, the novel 2D/2D S-scheme Bi12O15Cl6/BiOCl heterojunction was fabricated using a facile solvothermal followed by a post-thermal treatment process. The samples were characterized by various modern spectroscopy techniques. A series of Bi12O15Cl6/BiOCl heterojunctions were prepared by adjusting the molar ratio of Bi:Cl and the calcination temperature. The crystalline structure, morphology, elemental composition, and optical properties of nanocomposites strongly depend on the synthesis conditions. The sample prepared with Bi:Cl molar ratio of 2.0:1 and calcined at 400 °C (BOC-2.0-400) containing 29.55 wt% of BiOCl and 70.45 wt% of Bi12O15Cl6, exhibited the highest efficiency in the degradation of CIP solution under simulated solar light irradiation. The reaction rate constant was 2.5 times and 1.8 times higher than that of pristine BiOCl and Bi12O15Cl6, respectively. Under the experimental conditions of catalyst dosage of 0.7 gL-1, initial CIP concentration of 10 mgL-1 and pH8.8, CIP was completely degraded within 150 min of irradiation over the BOC-2.0-400. Furthermore, radical scavenging studies signified that O2●–, h+ are evolved in photocatalytic process. The experimental and characterization results provided evidenc that the excellent photocatalytic performance of Bi12O15Cl6/BiOCl heterojunction was facilitated by the construction of S-scheme charge transfer route with compact interface of 2D/2D morphology. The S-scheme Bi12O15Cl6/BiOCl heterojunction exhibited excellent visible light absorption ability, high photogenerated charge separation efficiency and maintained strong redox capacity for electrons and holes during CIP photodegradation. These findings provide a potential strategy for designing S-scheme heterojunction-based bismuth-rich bismuth oxyhalide photocatalyst to eliminate antibiotic residues.

Well-designed α-Fe2O3/ZnFe2O4 heterojunction for photocatalytic CO2 reduction to fuels

Spinel ZnFe2O4 photocatalyst has been widely applied in CO2 reduction due to its negative enough conduction band edge and relatively narrow band gap, which enable the generation of strong reduction electrons in the presence of light irradiation. Unfortunately, the catalytic performance of pure ZnFe2O4 was seriously hindered because of inefficient charge transfer. Here, Z-scheme α-Fe2O3/ZnFe2O4 heterojunctions were synthesized by coupling α-Fe2O3 nanosheets with spinel ZnFe2O4 nanoparticles and applied to the photoreduction of CO2. The α-Fe2O3/ZnFe2O4 heterojunctions realized high charge separation efficiency and strong redox ability. As a result, the CH4 generation rate of α-Fe2O3/ZnFe2O4 heterojunctions was 2.6 times higher than that of ZnFe2O4. This work exhibits a new strategy to design ZnFe2O4-based Z-scheme heterojunction for converting CO2 to hydrocarbon fuels.

Fabrication of dual-functional heterostructured p-CuO/n-ZnS nanocomposite for enhanced visible-light active photocatalytic response and fluorometric sensor for selective sensing of thiol-containing amino acids

In this study, CuO, ZnS, and p-CuO/n-ZnS heterojunction composites were synthesized using a simple co-precipitation method for investigating their photocatalytic properties for dye degradation and fluorescence sensing of thiol-containing amino acids at room temperature. The synthesized CuO, ZnS, and p-CuO/n-ZnS heterostructures were analyzed using UV–vis, PL, XRD, and TEM. The results showed that the heterostructure exhibited enhanced absorption in the visible light range, and synthesized materials have spherical shape with an average particle size is 12 ± 5 nm. The photocatalytic activities of CuO, ZnS, and p-CuO/n-ZnS heterostructures were evaluated by the degradation of various dyes such as MB, MO, and MR under visible light irradiation. The p-CuO/n-ZnS heterostructure showed the best photocatalytic efficiency, with degradation rates of 98.3%, 94.2%, and 92.8% for MB, MO, and MR dyes, respectively, compared to CuO NPs (72.5%, 75.8%, and 73.5%) and ZnS NPs (76.2%, 79.1%, and 78.3%) within a 35 min of reaction. The enhanced photocatalytic efficiency of the p-CuO/n-ZnS heterostructure was attributed to its high charge separation efficiency, which remained stable for up to five cycles without any significant loss of activity. Furthermore, the p-CuO/n-ZnS heterostructure was used as a fluorescent sensor for detecting thiol-containing amino acids such as cysteine (Cys) and methionine (Met). The results showed that the heterostructure had good sensing performance for Cys and Met within the range of 1–100 μM, with a detection limit of 2.52 μM (Cys) and 5.14 μM (Met) based on the linear calibration range. Moreover, p-CuO/n-ZnS composite was used to detect Met in human serum and urine samples.