Interfacial Charge Research Articles

Engineering of MnTe/MnO Heterostructures with Interfacial Electric Field Modulation for Efficient and Durable Li–O2 Batteries

AbstractDesign and synthesis of highly active and robust bifunctional cathode catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are of vital significance for practical applications of lithium–oxygen (Li–O2) batteries. Herein, a built‐in electric field (BIEF) strategy is reported to fabricate MnTe/MnO heterostructures with a large work function difference (ΔΦ) as a bifunctional cathode catalyst in Li–O2 batteries. The MnTe/MnO heterostructures with nanosheets and microporous structures result in an abundance of exposed active sites and facilitate mass transfer. More importantly, the heterogeneous MnTe/MnO nano‐interface region provides a BIEF that can trigger interfacial charge redistribution, fine‐tune the adsorption energy of oxygen intermediates, and alter the morphology of discharge products to accelerate ORR/OER kinetics. Impressively, the fabricated Li–O2 batteries with MnTe/MnO cathode showcases exhibit excellent electrochemical performances, including low charging overpotential, a high specific capacity of 11930 mA h g−1, and good cycle stability over 350 cycles even with a fixed specific capacity of 500 mA h g−1 at a current density of 500 mA g−1. This work provides an avenue for the rational design of high performance heterostructure electrocatalysts toward practical applications for rechargeable Li–O2 batteries.

Synergistic Schottky contacts & diatomic doping in Cr/P-MoS2@Ti3C2Tx with boosted energy storage performance

Molybdenum disulfide (MoS2), despite its promising attributes, suffers from low conductivity and aggregation. Herein, we introduce a novel approach that integrates Schottky contacts with Cr/P diatomic doping in MoS2@Ti3C2Tx, significantly enhancing its performance. The Schottky contacts effectively suppress aggregation and accelerate interfacial charge transfer, while Cr/P doping boosts conductivity, active sites, and stability. As a result, the Cr/P-MoS2@Ti3C2Tx electrode exhibits a specific capacitance of 650 F g-1 at 1 A g-1, which is fourfold higher than that of pristine MoS2. When assembled into an asymmetric supercapacitor (Cr/P-MoS2@Ti3C2Tx//AC ASC), the device achieves a peak energy density of 32 Wh kg-1 at 303 W kg-1, maintaining 85% capacitance retention after 10,000 cycles with an impressive coulombic efficiency of 97%. Furthermore, the density functional theory (DFT) calculations validate the beneficial effects of Schottky contacts and diatomic doping on the improved energy storage performance of Cr/P-MoS2@Ti3C2Tx. This work demonstrates the promising potential of the material for applications in high-performance supercapacitors (SCs).

Dirac Electrons with Molecular Relaxation Time at Electrochemical Interface between Graphene and Water.

The time dynamics of charge accumulation at the electrochemical interface between graphene and water is important for supercapacitors, batteries, and chemical and biological sensors. By using impedance spectroscopy, we have found that measured capacitance (Cm) at this interface with the gate voltage Vgate ≈ 0.1 V follows approximate laws Cm~T1.2 and Cm~T0.11 (T is Vgate period) in frequency ranges (1000-50,000) Hz and (0.02-300) Hz, respectively. In the first range, this dependence demonstrates that the interfacial capacitance (Cint) is only partially charged during the charging period. The observed weaker frequency dependence of the measured capacitance (Cm) at frequencies below 300 Hz is primarily determined by the molecular relaxation of the double-layer capacitance (Cdl) and by the graphene quantum capacitance (Cq), and it also implies that Cint is mostly charged. We have also found a voltage dependence of Cm below 10 Hz, which is likely related to the voltage dependence of Cq. The observation of this effect only at low frequencies indicates that Cq relaxation time is much longer than is typical for electron processes, probably due to Dirac cone reconstruction from graphene electrons with increased effective mass as a result of their quasichemical bonding with interfacial molecular charges.

Osmolyte-Induced Modulation of Hofmeister Series.

Natural selection has driven the convergence toward a selected set of osmolytes, endowing them with the necessary efficiency to manage stress arising from salt diversity. This study combines atomistic simulations and experiments to investigate how two osmolytes, glycine and betaine, individually modulate the Hofmeister ion ordering of alkali metal salts (LiCl, KCl, and CsCl) near a charged silica interface. Both osmolytes are found to prevent salt-induced aggregation of the charged entities, yet their mode and degree of relative modulation depend on their intricate interplay with specific salt cations. Betaine's ion-mediated surface interaction maintains Hofmeister ion ordering, whereas glycine alters the relative Hofmeister order of the cation by salt-specific ion desorption from the surface. Experimental validation through surface-enhanced Raman spectroscopy supports these findings, elucidating osmolyte-mediated alterations in interfacial water structures. These observations based on an inorganic interface are reciprocated in amyloid beta 40 dimerization dynamics, highlighting osmolytes' efficacy in mitigating salt-induced aggregation. A molecular analysis suggests that the differential modes of interaction, as found here for glycine and betaine, are prevalent across classes of zwitterionic osmolytes.

An Efficient Strategy for Tailoring Interfacial Charge Transfer Pathway on Semiconductor Photocatalysts: A Case of (BiFeO3)x(SrTiO3)1−x/Mn3O4

AbstractThe ability to generate heterostructures with a desirable charge transfer pathway is essential for achieving semiconductor photocatalysts with super photocatalytic activity. Herein, it is proposed to realize robust tailoring of effective charge transfer pathway in semiconductor‐based heterostructures via work function regulation, and elucidate the influence of the work function of the semiconductor on the charge transfer mechanism at the heterostructure interface. Specifically, taking type‐II heterostructure SrTiO3/Mn3O4 as an example, introducing BiFeO3 into SrTiO3 effectively regulate the work function of the (BiFeO3)x(SrTiO3)1−x/Mn3O4 (BxT1−x/Mn3O4) solid solution through optimizing the x value. Combined with in situ testing, the results show that the original type‐II heterojunction SrTiO3/Mn3O4 is converted into S‐scheme heterojunction (BiFeO3)0.3(SrTiO3)0.7/Mn3O4 when BiFeO3 is introduced. This increases the work function of the semiconductor, inducing the light‐generated carriers to be guided and separated by the generated built‐in electric field. Therefore, the implementation of this strategy can achieve efficient photocatalytic CO2 reduction. In contrast to pristine SrTiO3/Mn3O4, the (BiFeO3)0.3(SrTiO3)0.7/Mn3O4 heterostructure exhibits a 28‐fold enhancement of in electron consumption rate during photocatalytic CO2 reduction, and the reaction mechanism is suggested. In this study, a strategy for effectively converting interfacial charge transfer pathways in semiconductor photocatalysts is developed to enhance the photoconversion kinetics of CO2 and H2O.

Nitrogen-doped ZnIn2S4 and TPA multi-dimensional synergistically enhance photocatalytic hydrogen production

To alleviate the environmental pollution and energy crisis caused by the excessive use of fossil fuels, photocatalytic water splitting to produce hydrogen is an important way to solve energy and environmental problems. Here, Nitrogen-doped ZnIn2S4 (N-ZIS) composite tungsten-based polyoxometalate (TPA) composites (denoted as N-ZIS/TPA) were synthesized by a one-step solvothermal method. The introduction of N3– instead of S2− in ZIS changes the internal electron arrangement of ZIS, improves the electronegativity of ZIS, and is conducive to the surface adsorption of positively charged H*. At the same time, the impurity energy level is generated at the valence band position, which narrows the band gap and broadens the light absorption range, thereby promoting photocatalytic hydrogen production. After compounding, due to the adjustable redox properties of TPA itself, the internal W6+ part is reduced to W4+, resulting in the coexistence of W6+ and W4+ in the composite material, which fully verifies the flow of interface electrons from N-ZIS to TPA. The close contact between N-ZIS and TPA and the built-in electric field’s driving force help achieve efficient interfacial charge transfer. At the same time, W6+/W4+ redox pairs were introduced to accelerate the separation of photogenerated electrons and holes. The photocatalytic hydrogen production rate of the best sample 1N-ZIS/TPA-15 is as high as 17345.53 μmol·g−1·h−1, which is 2.92 times that of N-ZIS (5940.08 μmol·g−1·h−1) and 8.03 times that of ZIS (2159.22 μmol·g−1·h−1). This study explores the design and construction of efficient s-type heterojunctions by adjusting the energy band position of ZnIn2S4 as a new strategy in the field of photocatalytic hydrogen production.

Engineering of charge density at the anode/electrolyte interface for long-life Zn anode in aqueous zinc ion battery.

The aqueous zinc ion battery emerges as the promising candidate applied in large-scale energy storage system. However, Zn anode suffers from the issues including Zn dendrite, Hydrogen evolution reaction and corrosion. These challenges are primarily derived from the instability of anode/electrolyte interface, which is associated with the interfacial charge density distribution. In this context, the recent advancements concentrating on the strategies and mechanism to regulate charge density at the Zn anode/electrolyte interface are summarized. Different characterization techniques for charge density distribution have been analysed, which can be applied to assess the interfacial zinc ion transport. Additionally, the charge density regulations at the Zn anode/electrolyte interface are discussed, elucidating their roles in modulating electrostatic interactions, electric field, structure of solvated zinc ion and electric double layer, respectively. Finally, the perspectives and challenges on the further research are provided to establish the stable anode/electrolyte interface by focusing on charge density modifications, which is expected to facilitate the development of aqueous zinc ion battery.

Space charge effects in mixed ionic-electronic conducting electrodes for solid-state batteries.

Mixed ionic-electronic conductors are widely used as electroactive materials in energy applications. The contact of a mixed conductor with another phase plays a crucial role in charge storage and transport in energy devices. However, the interfacial chemistry at the heterojunctions comprising mixed conductors and its interplay with the bulk chemistry remains imperative yet inadequately understood. This study addresses the fundamentals of space charge effects by exploring the equilibrium situations for contacts consisting of mixed conductors. From the perspective of defect chemistry, and by unifying the bulk and interfacial conditions with the electrochemical potential, our treatment allows for predicting the built-in potential at heterojunctions, profiling the space charge distributions, and evaluating the resulting interfacial charge storage and transport. The treatment can be related to experimental characterization, including coulometric titration, conductivity, and capacitance measurements at electrochemical interfaces in all-solid-state batteries. Besides, our treatment also highlights the significance of size and doping effects in nanocrystalline electrodes. This work provides a comprehensive framework for understanding and engineering the heterojunctions in electrochemical devices.

Electrochemical-mechanical coupled interfacial degradation model of Ternary polymer composite cathodes in all-solid-state batteries

Despite significant attention focused on the composite cathode composed of active particles, which is considered to increase the interfacial areas and satisfy high areal load, suffers from interfacial issues. In this article, we formulate an electrochemical-mechanical model of LiNixMnyCozO2 (NMC) composite cathode coupling the relations between interfacial degradation, charge transformation, diffusion transport, and mechanical deformation under cyclic loads. Based on the transition state theory, we regard the interfacial degradation as an energy barrier dependent on the interfacial debonding state. Physical mismatch due to chemical expansion results in interfacial current distinction, anisotropic Li diffusion and excessive local stress. Compared to single-crystal NMC particles, the effect of interfacial separation and internal cracks triggers an extremely nonuniformity of Li distribution within random orientation polycrystalline-type particles. The external pressure in the range of operation can cause mechanical deformation to fill in the interface vacancies, which effectively alleviates the rapid growth of damage and provides a better cyclic performance. Moreover, soft polymer-based solid electrolytes take advantage of their flexible property to deal with solid-solid contact, providing considerable maintenance of interface stability. This present framework reveals the failure mechanism with electrochemical-mechanical coupled relations for composite cathode materials and broadens the design guidance toward improving interfacial integrity.

Enhanced photocatalytic performance of ternary g-C3N4/UiO-66/Ag3VO4 composite for methylene blue degradation under visible light irradiation

Anovel Ag3VO4/UiO-66/g-C3N4-based photocatalystwassynthesized using the solvothermal approach and characterized using XRD, SEM, FTIR, PL, and UV–Vis DRS. The photodegradation capacityof each componentwas tested using aqueous solutions of methylene blue (MB) and real sample solutions. It was found that the ternary composites (g-C3N4/UiO-66/Ag3VO4, 1 wt%, 5 wt%, 10 wt%, and 15 wt% g-C3N4) demonstrated higher degradation efficiency than the single and binary constituentsowing to beneficial interactions in the composite, which favor successful interfacial charge transfer and improve photogeneratede--h+pair separations. The influence of various experimental factors such as pH, initial dye amount, photocatalyst dose, and scavengers on MB degradation was examined. At optimal conditions of pH 6, catalyst load of 60 mg, and initialdye content of 10 ppm, the percent photodegradation of MB under irradiation with visible light (indoorsystem) was 99.35 %, while in the outdoor system,it was 99.5 % in 240 min. The selected photocatalyst was also applied for the degradation of real sewage sample solution, which was found to be 80.2 % under indoor and 89 % under outdoor experimental undertakings. After five cycles, the potential of the photocatalystremained substantial, indicating remarkable reusability. The scavenging experiment suggested that the principal active species were found to be superoxide (O2•) and hydroxide radicals (•OH). Thus, the composite g-C3N4/UiO-66/Ag3VO4 could be a promising option for industrial effluent removalapplications, particularly in the purification of organic dye-containing wastewater.

Boosting photocatalytic H2 evolution in B-doped g-C3N4/O-doped g-C3N4 through synergistic band structure engineering and homojunction formation

Photocatalytic hydrogen production is a promising method to address the increasing energy demand and depletion of fossil fuels. Among various photocatalysts, g-C3N4 (CN) has attracted significant attention due to its favorable properties and tunable band structure. CN-based heterojunctions have been developed to enhance photocatalytic efficiency through improved charge separation via interfacial charge transfer. However, traditional heterojunctions formed between CN and other semiconductors often face challenges related to material compatibility and stability. In this work, we explored the formation of homojunctions, which involve identical semiconductors and offer superior charge separation and electron mobility due to perfect lattice matching. To further enhance individual oxidation and reduction capabilities, we employed band structure engineering through B doping and O doping. The homojunction between B-doped CN (BCN) and O-doped CN (OCN) was successfully synthesized using simple electrostatic self-assembly, resulting in significantly improved hydrogen production of 519.3 μmol g−1h−1 compared to BCN (34.7 μmol g−1h−1) and CN (167.2 μmol g−1h−1). This approach enhances visible light absorption, charge separation, and mobility, demonstrating the potential for developing advanced CN-based photocatalysts for various applications.

Constructing type II heterojunction of 2D/1D Pg-C3N4/Ag3VO4 nanocomposite with high interfacial charge separation for boosting photocatalytic CO2 reduction under solar energy

The well-designed, template-free synthesis of 2D protonated g-C3N4 nanosheets (Pg-C3N4) coupled with novel 1D Ag3VO4 nanorods has been investigated to construct 2D/1D interface heterostructures with strong electrostatic interactions between the positively charged 2D Pg-C3N4 nanosheets and the negatively charged 1D Ag3VO4 nanorods. The coupling of Pg-C3N4 and Ag3VO4 with desirable characteristics resulted in a 2D/1D interface heterojunction with a type II charge carrier transfer mechanism, effectively maintaining and utilizing charge carriers. The 2D/1D Pg-C3N4/Ag3VO4 exhibited remarkable photocatalytic performance for CO2 conversion with H2O, resulting in maximum CH4 and dimethyl ether (DME) production of 352.3 and 130.9 µmol/g-cat, respectively. A quantum yield of 0.23 % for CH4 generation was achieved over the 2D/1D Pg-C3N4/Ag3VO4, which was 2.9 and 1.4 times higher than that of the Pg-C3N4 and Ag3VO4 samples, respectively. The improvement in photocatalytic performance primarily stems from the effective interaction between Pg-C3N4 and ternary Ag3VO4, leading to enhanced transfer and separation of photoinduced charge carriers through the creation of a type II heterojunction. The findings of this study are useful in designing template-free heterojunctions for photocatalytic CO2 conversion and other solar energy applications.

Facilitating superior electrochemical efficacy and ultra rapid kinetic in Co/Ni-free layered oxides for sodium-ion batteries with phosphate-growing layer fast ion conductors

Co/Ni-free layered oxides have garnered significant interest due to their environmental friendliness and facile synthesis methodologies, while facing major challenges of inferior cycling stability and rate capability. Addressing these drawbacks necessitates the enhancement of the surface properties of Co/Ni-free layered oxides. This work introduces a Co/Ni-free layered oxide, Na0.67Mn0.65Fe0.3Al0.05O2 (NMFA), which has been subjected to phosphate-based surface engineering. This targeted surface modification aims to augment the specific surface area and establish a protective layer on NMFA. Such improvements are critical for expanding the effective electrochemical reaction zone, broadening sodium ion diffusion pathways, curtailing the P2-OP4 phase transition, and reducing the activation energy for interfacial charge transfer. This multifaceted surface treatment epitomizes the ingenious design and realization of advanced Co/Ni-free layered oxide cathode materials through straightforward processing techniques. Notably, the NMFA subjected to 3%-AlPO4 surface modification demonstrated an initial discharge capacity of 189.1 mAh/g at 0.1C, maintaining its capacity after 500 cycles at 10C. Additionally, DFT calculations corroborate that such surface growth can bolster electrical conductivity, restrain oxygen liberation and foster sodium ion migration. This elucidates that the phosphate growth layer serves as the oxygen reservoir. Accordingly, this investigation propounds a promising avenue to circumvent the challenges confronting Co/Ni-free layered oxides, thus paving the way for the development of high-performance cathode materials.

Phase Dependence of Surface Charge Measurement on Epoxy Insulator in C4F7N/CO2 under AC Voltage.

The application of binary gas mixtures consisting of heptafluorobutyronitrile (C4F7N) and carbon dioxide (CO2) in AC GIS is currently attracting much attention. Therefore, the evaluation of the gas-solid interface charge distribution characteristics of epoxy resin is indispensable. Additionally, the phase-dependency of the charging behavior remains not fully understood. We simulated coaxial electrode structure in GIS and investigated the surface charge distribution on a down-scaled epoxy insulator. The influence of the truncated phase angle and duration of AC voltage on charge behavior were analyzed, and the charge transport mechanism under AC voltage was theoretically analyzed. The results showed that there was a noticeable negative charge speckle with the presence of the metal particle and the accumulated negative charge on the insulator surface far exceeded that of the positive charge. The maximum surface charge density and the amount of surface charge accumulated first increased and then decreased over time. It was found that the phase angle has a negligible influence on the surface charge distribution at the cut-off moment.

Pure-Phase Perovskite Quantum Well for Green Light-Emitting Diodes.

Perovskite multiple quantum wells (MQWs) have shown great potential in the field of light-emitting diodes (LEDs). However, the random formation of QWs with varying well widths (n numbers) often leads to suboptimal interface defects and charge transport issues. Here, we reveal that the crystallization sequence of bromide-based perovskite MQWs is large-n QWs preceding small-n QWs. With this insight, we prevent the crystallization of subsequent small-n QWs by reducing the crystallization rate, ultimately resulting in the crystallization of only n = 5 QWs. This reduction in the crystallization rate is achieved through the chemical interaction of dual additives with perovskite constituents. Additionally, the chemical interaction effectively passivates the uncoordinated lead ions defects. Consequently, pure-phase perovskite QWs with a high photoluminescence quantum efficiency of 75% are achieved. The resulting green LEDs achieve a peak external quantum efficiency of 17.1% and a maximum luminance of 29,480 cd m-2, which is attractive for full-color display applications of perovskites.

Coupling monoclinic Pb2(CrO4)O with Mn3O4 quantum dots as oxygen vacancies-rich S-scheme photocatalysts for visible-light-driven photocatalytic CO2 reduction with H2O

Simulating natural photosynthesis to convert CO2 and H2O into fuels achieving overall reaction is a promising solution for addressing environmental problems and energy crises. Constructing an S-scheme catalyst of two or more catalytic sites with rapid electron transfer and strong redox capability may be an effective strategy for coupling photocatalytic CO2 reduction and H2O oxidation. Here, an oxygen vacancies-rich S-scheme semiconductor photocatalyst composed of monoclinic lead chromate oxide (Pb2(CrO4)O) coupled with Mn3O4 quantum dots (QDs) (Pb2(CrO4)O@Mn3O4QDs) are synthesized and tested for photoconversion of CO2 with H2O under visible light. Through the integration of Pb2(CrO4)O with Mn3O4QDs, the photocatalytic C1-evolution rate on Pb2(CrO4)O@Mn3O4QDs is radically increased by 6.0 and 8.1 times, which is much faster than that of pristine Pb2(CrO4)O and Mn3O4. The origin of the greatly raised activity is revealed by advanced characterizations, and in situ X-ray photoelectron spectroscopy (XPS) confirms the electron transport pathway in Pb2(CrO4)O@Mn3O4QDs with light illumination, unveiling the efficient spatial separation/transfer of charge carriers in oxygen vacancies-rich Pb2(CrO4)O@Mn3O4QDs S-scheme heterojunction. Consequently, powerful photoelectrons and holes accumulate in the Mn3O4 conduction band and Pb2(CrO4)O valence band, respectively, exhibiting prolonged long lifetimes and facilitating their involvement in CO2 photoreduction and H2O photooxidation through altering the interfacial charge dynamics.

Carbon Doping Regulates Charge Transfer Paths via a Type-II to S-Scheme Transformation to Improve Photocatalytic Performance.

Designing S-scheme heterojunctions with enhanced interfacial interaction is an effective strategy for promoting the separation of photocarriers while maintaining strong photoredox capabilities. However, precisely tailoring the interfacial charge transport pathways between two contacted semiconductors remains a significant challenge due to the similar band alignment in type-II and S-scheme heterostructures. Herein, we report a facile and low-cost carbon doping strategy to smartly tune the charge transfer pathway via a type-II to S-scheme transformation for efficient photocatalytic H2 evolution and H2O2 synthesis. Density functional theory calculations combined with in situ XPS studies demonstrate that the Fermi level of MoO2 shifts from being higher than that of C3N4 to being lower after carbon doping, which drives the inversion of the internal electric field (IEF) direction between MoO2 and C3N4, thus enabling a transition from type-II MoO2/C3N4 heterojunctions to S-scheme C-MoO2/C3N4 heterojunctions. As a result, the optimal S-scheme C-MoO2/C3N4 heterojunctions exhibit a high H2 evolution rate of 16.2 mmol g-1 h-1 and a H2O2 production rate of 877 μmol g-1 h-1, notably surpassing those of the original C3N4 and type-II MoO2/C3N4 heterojunctions. This work provides valuable insights into the fabrication of C3N4 heterostructures and the control of electron migration pathways, thereby creating new possibilities for photocatalysis and optoelectronics applications.

One-Step Self-Assembled WO3/rGO Microspheres Photoanode Assembled Efficient Photocatalytic Fuel Cells for Simultaneous Organic Pollutant Degradation and Electricity Generation.

Photocatalytic fuel cells (PFCs) present a promising and environmentally friendly approach to simultaneously treat organic pollutants in wastewater and electricity generation. The development of photoanodes with high light absorption and carrier mobility is essential for enhancing the performance of PFCs but remains challenging. Herein, a one-step self-assembly strategy was adopted to develop flower-like WO3/rGO microspheres for PFC devices. Attributed to the abundant surface-active sites, enhanced light harvesting, and efficient separation of photogenerated charge carriers, the WO3/rGO photoanode demonstrated superior rhodamine B (RhB) degradation rate (90% in 2 h), maximum power density (4.74 μW/cm2), and maximum photocurrent density (0.096 mA/cm2), 1.4, 2.4, and 4.0 times higher than the corresponding pure WO3 photoanode, respectively. Density functional theory (DFT) calculations reveal that the built-in electric field formed between the interface of WO3 and rGO promotes the transfer of photogenerated electrons from WO3 to rGO, thus exerting a significant impact on improving the migration and separation of photoinduced charge carriers. Moreover, by combining experimental and theoretical results, a complete PFC operation mechanism for the PFC system was proposed. This study focuses on the strategy of constructing rGO-doped photocatalysts to enhance the interfacial charge transfer mechanism, providing a promising approach for the development of high-performance photoanodes in PFC systems.

Incorporating C3N5 and NiCo2S4 to Form a Novel Z-Scheme Heterojunction for Superior Photocatalytic Degradation of Norfloxacin

Due to a combination of increased urbanization, industrialization, and population growth, many pharmaceutical pollutants are currently being discharged into the environment. A possible strategy is critical for eliminating antibiotic pollutants from the environment, and photocatalysis has been generally recognized as an excellent method for successfully degrading antibiotics at a faster pace. In this work, we employed a hydrothermal synthesis approach to create a novel C3N5/NiCo2S4 Z-scheme-based heterojunction with better interfacial charge transfer and used it as a catalyst for the degradation of norfloxacin antibiotic. The optimized 1:1 C3N5/NiCo2S4 (50CN/NCS) shows the highest photocatalytic efficiency of 86.5% in 120 min towards the degradation of norfloxacin (NOR). Such an effective performance can be attributed to the high responsive nature of photocatalyst in the visible region and superior transfer of interfacial charges via Z-scheme transfer in heterojunction. The high charge transfer efficiency and reduced recombination of charge carriers in heterojunction was confirmed by EIS and PL results. The influence of some key factors such as pollutant concentration, catalyst dosage, pH, and coexisting ions on the photocatalytic activity is also investigated in this work. The optimized heterojunction 50CN/NCS also degraded 89.1%, 78.3%, and 93.2% removal of the other pollutants CIP, SDZ, and BPA, respectively.

Dual LSPR and CT synergy: 3D urchin-like Au@W18O49 enables highly sensitive in-situ SERS detection of dissolved furfural in insulating oils

Assessing the levels of furfural in insulating oils is a crucial technical method for evaluating the degree of aging and mechanical deterioration of oil-paper insulation. The surface-enhanced Raman spectroscopy (SERS) technique provides an effective method for enhancing the sensitivity of in-situ detection of furfural. In this study, a homogeneous three-dimensional (3D) urchin-like Au@W18O49 heterostructure was synthesized as a SERS substrate using a straightforward hydrothermal method. The origin of the superior Raman enhancement properties of the 3D urchin-like heterostructures formed by the noble metal Au and the plasmonic semiconductor W18O49, which is rich in oxygen vacancies, is analyzed experimentally in conjunction with density-functional theory (DFT) calculations. The Raman enhancement is further amplified by the remarkable dual localized surface plasmon resonance (LSPR) effect, which generates a strong local electric field and creates numerous "hot spots," in addition to the interfacial charge transport (CT). The synergistic effect of these factors results in the 3D urchin-like Au@W18O49 heterostructure exhibiting exceptionally high SERS activity. Testing the rhodamine 6G (R6G) probe resulted in a Raman enhancement factor of 3.41 × 10−8, and the substrate demonstrated excellent homogeneity and stability. Furthermore, the substrate was effectively utilized to achieve highly sensitive in-situ surface-enhanced Raman scattering (SERS) detection of dissolved furfural in complex plant insulating oils. The development of the 3D urchin-like Au@W18O49 heterostructure and the exploration of its enhancement mechanism provide theoretical insights for the advancement of high-performance SERS substrates.