Bulk Charge Research Articles

Gradient Surface Gallium-Doped Hematite Photoelectrode for Enhanced Photoelectrochemical Water Oxidation.

Hematite is a promising material for photoelectrochemical (PEC) water oxidation, but its photocurrent is limited by bulk charge recombination and poor oxidation kinetics. In this study, we report a high-performance Fe2O3 photoanode achieved through gradient surface gallium doping, utilizing a Ga2O3 overlayer on FeOOH precursors via atomic layer deposition (ALD) and co-annealing for Ga diffusion. The Ga-doped layer passivates surface states and modifies the band structure, creating a built-in electric field that enhances the charge separation efficiency. Following the electrodeposition of CoFeOx as a cocatalyst, the resulting CoFe-Ga:Fe2O3 photoanode exhibited a notable negative shift in onset potential by approximately 100 mV, a high photocurrent density of 2.6 mA cm-2 at 1.23 V versus RHE, and excellent long-term PEC stability over 40 h. This work presents an effective strategy for enhancing the PEC performance of photoelectrodes through advanced surface coatings.

Photocurrent switching effect and visible light activity of electrochemically synthesized bifunctional through oxide via TiO2/CuO composites

Photoelectrochemical conversion of solar energy into fuel products such as H2 or CH4 is an appealing, but technologically difficult process due to the simultaneous requirements for stability, efficiency and selectivity in the photoelectrode. One approach to design a photoelectrode with suitable properties is by using different materials that can complement each other. In this study, we introduce a novel approach by compositing TiO2 with CuO via electrodeposition of Cu into through-oxide vias/channels – a design that offers enhanced synergy between the materials. The Cu is then precisely transformed into Cu2O, CuO, or a mixture, based on annealing temperature, enabling tunable properties and optimized functionality. Unlike in traditional “sandwich” composites, this structuring reduces bulk charge carrier recombination through the formation of a depletion zone between TiO2 and CuO, allowing both materials to perform distinct functions. As a result, photocurrent switching is achieved by altering the applied potential, which is a functionality not previously demonstrated for photoactive composite materials. Our study also reports evidence of visible light sensitivity in TiO2/CuO composites when illuminated by a 4100K LED without UV components. Open circuit voltage decay measurements reveal that the improved charge carrier transport is due to the formation of a conductive Cu pathway—a novel finding that opens new possibilities for efficient photoexcitation. Although the charge carrier lifetimes were found to be shorter in TiO2/CuO electrodes compared to pure TiO2, we attribute this to the phenomenon of Cu "filling" the TiO2 channels and decreasing the available surface area, a trade-off that provides crucial insights into material design for future applications.

3D Structured Lithium Metal Anodes: A Comprehensive Analysis of Existing Work and Assessment of Performance Under Practical High Energy Density Cell Design

Lithium metal batteries (LMBs) are highly attractive for weight-limited applications due to their high theoretical gravimetric energy density. Advancements in recent years have yielded huge improvements in their cycle life and safety. However, LMBs still show capacity degradation and premature cell death due to the formation of dead lithium and electrolyte dry out in realistic cell design and testing. Current collectors with 3-dimensional structures have been proposed and studied extensively in recent years as an attempt to alleviate these issues. Three dimensional structures are claimed to improve performance by reducing local current density, restricting lithium volume expansion, stabilizing the solid-electrolyte interphase (SEI), improving the kinetics of lithium nucleation by providing additional lithium nucleation sites, and other justifications. However, despite the expansive literature published on the topic, no consensus has been reached as to what physical, chemical, and electrochemical properties of a 3D current collector are most likely to result in improved performance. This presentation focuses on two studies of 3D current collectors: (1) a meta-study reviewing literature data and analyzing the impact of key anode properties on the cycle life and Coulombic efficiency (CE); and (2) an experimental study on the electrochemical performance of four commercially available anode in combination with four different electrolytes.Analysis of published data using statistical methods and data science approaches (linear correlation coefficient calculations, self-organizing maps) show almost no consistent improvements of CE or cycle life based on frequently utilized strategies. Preliminary results suggest that there is no significant improvement with increasing surface area, altering pore diameter size, use of a lithiophilic coating or additive, nor any particular morphology. The only significant increase in CE noted is seen when a conductive coating or additive is utilized in the 3D structure compared to when an insulative coating is applied, though cycle life does not show a similar increase.Based on these insights, an experimental study is presented that compares four commercially available copper current collectors with different structures (foil, foam, punched foil, and layered punched foil on unaltered foil). These structures were chosen and left unaltered due to the lack of evidence in the literature data review of benefits arising from alterations. In addition to varying anode structure, four electrolytes are utilized, one conventional electrolyte and three state-of-the-art electrolytes, to determine if performance trends hold regardless of electrolyte used. Average CE values are determined over the course of a cycling protocol consisting of plating/stripping from a lithium reservoir, mimicking cycling in high energy density pouch cells. Changes in cell impedance are evaluated at multiple stages of cycling using electrochemical impedance spectroscopy (EIS), and the morphology of the SEI and the plated lithium metal is examined using cryo-focused ion beam scanning electron microscopy (cryo-FIB SEM) to give further insight into the behavior of lithium on the current collectors. Average CEs calculated from this testing show no statistically significant differences between any of the structures. Significant differences in CE are observed, however, when the varied electrolytes are employed. Evaluation of cell impedance changes during cycling shows similar bulk and interfacial charge transfer resistances between structures with consistent electrolyte. The conventional electrolyte demonstrates lower bulk resistance due to a slightly higher ionic conductivity than the state-of-the-art electrolyte yet greater charge transfer resistance, predicting worse long term performance. Morphological changes demonstrated increased lithium thickness, resulting in greater percentages of mossy lithium growth and more SEI formation over cycling for the conventional electrolyte, aligning with the observed charge transfer resistance. Differences in plated lithium density are also observed between substrates regardless of electrolyte, informing on their application for lean electrolyte conditions.In all, the experimental study indicates that electrolyte chemistry has a greater effect on the efficiency and morphology of lithium plating and stripping than current collector architecture when excess lithium is used in cell design. Based on the results presented, punched copper foil is proposed to be the ideal current collector for quick scale-up practical high energy density LMBs due to high CE in newer generation electrolytes and lower mass than the other tests substrates.

Giant Charge Separation-Driving Force Together with Ultrafluent Charge Transfer in TiO2/ZnFe-LDH Photoelectrode via Ferroelectric Interface Engineering.

Hydrogen fuel production using photoelectrochemical (PEC) water-splitting technology is incredibly noteworthy as it provides a sustainable and clean method to alleviate the energy environmental crisis. A highly rapid electron shuttle at the semiconductor/WOC (water oxidation cocatalyst) interface is vital to improve the bulk charge transfer and surface reaction kinetics of the photoelectrode in the PEC water-splitting system. Yet, the inevitably inferior interface transition tends to plague the performance enhancement on account of the collision of hole-electron transport across the semi/cat interface. Herein, we address these critical challenges via inserting ferroelectric layer BTO (BaTiO3) into the semi/cat interface. The embedded polarization electric field induced by ferroelectric BTO remarkably pumped hole transfer at the semiconductor/WOC (TiO2/ZnFe-LDH) interface and selectively tailored the electronic structure of LDH surface-active sites, leading to overwhelmingly improved surface hole transfer kinetics at LDH/electrolyte interface, which minish the electron-hole recombination in bulk and on the surface of TiO2. The TiO2 nanorods encapsulated by ferroelectric-assisted ZnFe-LDH achieve 105% charge separation efficiency improvement and 53.8% charge injection efficiency enhancement compared with pure TiO2. This finding offers a strategic design for electrocatalytic-assisted photoelectrode systems by ferroelectric-pumped charge extraction and transfer at the semiconductor/WOC interface.

Absence of bulk charge density wave order in the normal state of UTe2

A spatially modulated superconducting state, known as pair density wave (PDW), is a tantalizing state of matter with unique properties. Recent scanning tunneling microscopy (STM) studies revealed that spin-triplet superconductor UTe2 hosts an unprecedented spin-triplet, multi-component PDW whose three wavevectors are indistinguishable from a preceding charge-density wave (CDW) order that survives to temperatures well above the superconducting critical temperature, Tc. Whether the PDW is the mother or a subordinate order remains unsettled. Here, based on a systematic search for bulk charge order above Tc using resonant elastic X-ray scattering (REXS), we show that the structure factor of charge order previously identified by STM is absent in the bulk within the sensitivity of REXS. Our results invite two scenarios: either the density-wave orders condense simultaneously at Tc in the bulk, in which case PDW order is likely the mother phase, or the charge modulations are restricted to the surface.

Sensitive Self-Driven Single-Component Organic Photodetector Based on Vapor-Deposited Small Molecules.

Typically, organic solar cells (OSCs) and photodetectors (OPDs) comprise an electron donating and accepting material to facilitate efficient charge carrier generation. This approach has proven successful in achieving high-performance devices but has several drawbacks for upscaling and stability. This study presents a fully vacuum-deposited single-component OPD, employing the neat oligothiophene derivative DCV2-5T in the photoactive layer. Free charge carriers are generated with an internal quantum efficiency of 20 % at zero bias. By optimizing the device structure, a very low dark current of 3.4 · 10-11Acm-2 at -0.1V is achieved, comparable to the dark current of state-of-the-art bulk heterojunction OPDs. This optimization results in specific detectivities of 1· 1013Jones (based on noise measurements), accompanied by a fast photoresponse (f-3dB = 200kHz) and a broad linear dynamic range (>150dB). Ultrafast transient absorption spectroscopy unveils that charge carriers are already formed at very short time scales (<1ps). The surprisingly efficient bulk charge generation mechanism is attributed to a strong electronic coupling of the molecular exciton and charge transfer states. This work demonstrates the very high performance of single-component OPDs and proves that this novel device design is a successful strategy for highly efficient, morphological stable and easily manufacturable devices.

Fe-N Co-Doped BiVO4 Photoanode with Record Photocurrent for Water Oxidation.

Bismuth vanadate (BVO) ranks among the most promising photoanodes for photoelectrochemical (PEC) water splitting. Nonetheless, slow charge separation and transport, besides the sluggish water oxidation kinetics, are key barriers to its photoefficiency. Here, we present a co-doping strategy that significantly improves the charge separation performance of BVO photoanodes. We found that, under standard one sun illumination, the Fe-N co-doped BVO photoanode (Fe-N-BVO) by N-coordinated Fe precursor reaches a record photocurrent density of 7.01 mA cm-2 at 1.23 V vs RHE after modified a surface co-catalyst (FeNiOOH), and exhibits an outstanding stability. By contrast, much lower photocurrent density is obtained for the N-doped, Fe-doped and Fe/N-doped BVO photoanode with separated N and Fe precursors. The detailed experimental characterizations show that the high activity of the Fe-N co-doped BVO photoanode is attributed to the enhanced photo-induced bulk charge separation, as well as the accelerated surface water oxidation kinetics. XPS, EXAFS and DFT calculations clearly show that, instead of formation of deep trapping state in the individually doped BVO, the co-doping of Fe-N into BVO generates Fe-based electronic states just below the bottom of conduction band and N-derived states just above the top of valence band. Such modulations in electronic structure enable the efficient trap of the electrons and holes to enhance the separation of photo-induced carriers, but hinder the charge recombination originated from the deep trapping sites.

Fe−N Co‐Doped BiVO4 Photoanode with Record Photocurrent for Water Oxidation

AbstractBismuth vanadate (BVO) ranks among the most promising photoanodes for photoelectrochemical (PEC) water splitting. Nonetheless, slow charge separation and transport, besides the sluggish water oxidation kinetics, are key barriers to its photoefficiency. Here, we present a co‐doping strategy that significantly improves the charge separation performance of BVO photoanodes. We found that, under standard one sun illumination, the Fe−N co‐doped BVO photoanode (Fe−N−BVO) by N‐coordinated Fe precursor reaches a record photocurrent density of 7.01 mA cm−2 at 1.23 V vs RHE after modified a surface co‐catalyst (FeNiOOH), and exhibits an outstanding stability. By contrast, much lower photocurrent density is obtained for the N‐doped, Fe‐doped and Fe/N‐doped BVO photoanode with separated N and Fe precursors. The detailed experimental characterizations show that the high activity of the Fe−N co‐doped BVO photoanode is attributed to the enhanced photo‐induced bulk charge separation, as well as the accelerated surface water oxidation kinetics. XPS, EXAFS and DFT calculations clearly show that, instead of formation of deep trapping state in the individually doped BVO, the co‐doping of Fe−N into BVO generates Fe‐based electronic states just below the bottom of conduction band and N‐derived states just above the top of valence band. Such modulations in electronic structure enable the efficient trap of the electrons and holes to enhance the separation of photo‐induced carriers, but hinder the charge recombination originated from the deep trapping sites.

Triggering Asymmetric Layer Displacement Polarization and Redox Dual-Sites Activation by Inside-Out Anion Substitution for Efficient CO2 Photoreduction.

Sluggish bulk charge transfer and barren catalytic sites severely hinder the CO2 photoreduction process. Seeking strategies for accelerating charge dynamics and activating reduction and oxidation sites synchronously presents a huge challenge. Herein, an inside-out chlorine (Cl) ions substitution strategy on the layered polar Bi4O5Br2 is proposed for achieving layer structure-dependent polarization effect and redox dual-sites activation. Cl ions in the bulk phase shrink the halogen layer interspace by 8‰, triggering asymmetric [Bi4O5]2+ layer displacement polarization, prolonging the average photocharge lifetime to 201.8ps. Meanwhile, surface substituted Cl ions enhance the electron-donating capability of neighboring Bi atoms, activating the intrinsic Bi reduction sites, and increasing H2O molecule adsorption on nearby intrinsic O oxidation site (cal. by 0.105eV), also self-donating as an alien oxidation site. Besides, Cl upshifts the p-band center closer to the Fermi level, facilitating the reactant adsorption. Therefore, the energy barrier for CO2 activation and rate-limiting *COOH intermediate formation steps are significantly decreased. Without cocatalysts and sacrificial reagents, inside-out Cl-substituted Bi4O5Br2 delivers a remarkable CO2-to-CO photoreduction rate of 50.18µmol g-1 h-1, being one of the state-of-the-art catalysts. This finding offers insights into exploiting polarization at the molecular-level and enhances understanding of catalytic site activation.

Tailoring Carrier Dynamics of BiVO4 Photoanode via Dual Incorporation of Au and Co(OH)x Cooperative Modification for Photoelectrochemical Water Splitting

AbstractPhotoelectrochemical solar to hydrogen production is a promising way to achieve carbon neutrality, but severe charge recombination in photoanodes limits the conversion efficiency. Herein, Au nanoparticles and Co(OH)x co‐sensitized bismuth vanadate (BiVO4) to construct AuCo(OH)x/BiVO4 photoanode for significantly enhancing the performance of photoelectrochemical water splitting. This process significantly improves the bulk charge carrier separation efficiency, the surface kinetics of water oxidation, and the electron density of BiVO4 photoanode through Au surface plasmon resonance (SPR) and Co(OH)x oxygen evolution catalysts effect. Additionally, the enhancement of the *O and the *OOH generation accelerate the oxygen evolution reaction kinetics. Consequently, the constructed AuCo(OH)x/BiVO4 photoanode demonstrates an excellent photocurrent of 6.2 mA cm−2 at 1.23 V versus reversible hydrogen electrode and a stable continuous output within 42 h. This work contributes to developing high‐efficiency and high‐stability photoanodes for solar H2 production through SPR effect and oxygen evolution catalysts.

Oriented Crystal Polarization Tuning Bulk Charge and Single-Site Chemical State for Exceptional Hydrogen Photo-Production.

Rapid bulk charge recombination and mediocre surface catalytic sites harshly restrict the photocatalytic activities. Herein, the aforementioned concerns are well addressed by coupling macroscopic spontaneous polarization and atomic-site engineering of CdS single-crystal nanorods for superb H2 photo-production. The oriented growth of CdS nanorods along the polar axis, vectorially superimposing substantial polar units with orderly arrangement, renders a strong polarization electric field (20.1 times enhancement), which boosts bulk charge separation with an efficiency up to 72.4% (80.4-fold). Remarkably, polarization electric field alters the chemical state of Pt single sites by orderly reducing the binding energy of Pt atom with stepwise polarization enhancement of CdS substrate, which increases the onsite electron density of Pt from 10.232 to 10.261e- and *H key intermediates, providing preponderant Volmer-Tafel/Volmer-Heyrovsky reaction pathways with significantly decreased energy barriers for H2 production. Thus, highly polarized CdS nanorods with atomically dispersed Pt sites perform an outstanding H2 space-time yield of 118.5mmol g-1 h-1 and apparent quantum efficiency of 57.7% at λ = 420nm, and a record-high H2 turnover frequency of 57798.4 h-1, being one of the best catalysts for photocatalytic H2 evolution. This work highlights the function of polarization in manipulating charge separation and catalytic reaction.

Unmasking hidden ignition sources: A new approach to finding extreme charge peaks in powder processing

Powders acquire a high electrostatic charge during transport and processing. Consequently, in the aftermath of dust explosions, electrostatic discharge is often suspected to be the ignition source. However, definite proof is usually lacking since the rise of electrostatic charge cannot be seen or smelled, and the explosion destroys valuable evidence. Moreover, conventional methods to measure the bulk charge of powder flows, such as the Faraday pail, provide only the aggregate charge for the entire particle ensemble. Our simulations show that, depending on the flow conditions, contacts between particles lead to bipolar charging. Bipolar charged powder remains overall neutral; thus, a Faraday pail detects no danger, even though individual particles are highly charged. To address this gap, we have developed a machine learning-enhanced measurement technology to resolve the powder charge spatially. The first measurements have revealed a critical discovery: a localized charge peak near the inner wall of the conveying duct that is 85 times higher than the average charge that would be measured by the Faraday pail. This finding underscores the possibility of extremely high local charges that can serve as ignition sources, even though they remain undetected by conventional measurement systems. Our new technology offers a solution by spatially resolving the charge distribution within powder flows, unmasking hidden ignition sources, and preventing catastrophic incidents in the industry.

Construction of "Metal Defect/Oxygen Defect Junction" in ZnFe2O4-NiCo2O4 Heterostructures for Enhancing Electrocatalytic Oxygen Evolution.

Defect engineering is a promising approach to improve the conductivity and increase the active sites of transition metal oxides used as catalysts for the oxygen evolution reaction (OER). However, when metal defects and oxygen defects coexist closely within the same crystal, their compensating charges can diminish the benefits of both defect structures on the catalyst's local electronic structure. To address this limitation, a novel strategy that employs the heterostructure interface of ZnFe2O4-NiCo2O4 to spatially separate the metal defects from the oxygen defects is proposed. This configuration positions the two types of defects on opposite sides of the heterojunction interface, creating a unique structure termed the "metal-defect/oxygen-defect junction". Physical characterization and simulations reveal that this configuration enhances electron transfer at the heterostructure interface, increases the oxidation state of Fe on the catalyst surface, and boosts bulk charge carrier concentration. These improvements enhance active site performance, facilitating hydroxyl adsorption and deprotonation, thereby reducing the overpotential required for the OER.

High‐Brightness and High‐Resolution Triboelectrification‐Induced Electroluminescence Skin for Photonic Imaging and Information Interaction

AbstractSelf‐powered visualized sensor with skin‐like functionality is highly anticipated for practical application in health monitoring, human‐machine interaction, and robotics. However, the existing methods are disadvantaged by their poor performance in sensitivity and spatial fidelity due to the low pixel density, brightness, or conformability. Herein, a novel self‐powered skin‐inspired visualized sensor (SP‐SIVS) is developed by means of triboelectrification‐induced electroluminescence (TIEL) technique. By integrating surface and bulk charge generation with a high‐voltage corona charging treatment, a significant improvement is achieved in the brightness (by 10‐fold) and spatial resolution (100 µm) of the SP‐SIVS. Meanwhile, Young's modulus (94 kPa) is maintained at a level comparable to human skin, with tensile strength and elongation exceeding 1000 kPa and 1000%, respectively. Furthermore, SP‐SIVS is verified as applicable to serve such purposes as wearable motion detection, fingerprint morphology imaging, and information interaction. This work contributes an innovative framework to the development of SP‐SIVS with high‐brightness, high‐resolution, and sustainability, laying a foundation for its popularization as a novel interactive medium required for advanced photonic applications.

Deconvoluting Surface and Bulk Charge Storage Processes in Redox-Active Oxides by Integrating Electrochemical and Optical Insights.

Redox-active transition metal oxides (TMOs) play crucial roles in diverse energy storage and conversion technologies, such as batteries and pseudocapacitors. These materials show intricate electrochemical charge storage processes, encompassing both bulk ion-intercalation, typical of battery electrodes, and pseudocapacitive-like behavior localized near the surfaces. However, understanding the underlying mechanisms of charge storage in redox-active TMOs is challenging due to the coexistence of these behaviors. In this study, we propose an integrated approach that combines operando electrochemical and optical techniques to disentangle the contributions of bulk and surface phenomena. Using birnessite δ-MnO2-x as a model system, we account for surface pseudocapacitive-like layers and employ a refined model that incorporates both surface reactions and bulk chemical diffusion. This methodology allows us to extract essential kinetic parameters, establishing a fundamental framework for unraveling surface and bulk electrochemical processes. This advancement provides a valuable tool for the rational design of energy storage devices, enhancing our ability to tailor these materials for specific applications.

Construction of Br-Cu2O@NiFe-LDHs Z-scheme heterojunction and photocatalytic degradation of catechol

Facet regulation and construction of heterojunctions are important means to enhance the photocatalytic performance of single-phase materials. In this paper, the facet index of Cu2O was changed through Br doping, and then a Br doped Cu2O@NiFe-LDHs Z-scheme heterojunction (BC@LDHs) was constructed for photocatalytic degradation of catechol. The optimal conditions for photocatalytic degradation reaction were explored; the kinetic and thermodynamic parameters of the reaction, as well as the stability and reusability of the material were studied. Under optimal reaction conditions, the photocatalytic degradation of catechol can reach up to 95.68 % by BC@LDHs, which is much higher than that of single-phase materials and Cu2O@LDHs. By combining experiments and theoretical calculations, the intrinsic reasons and mechanisms for Br doping to enhance the photocatalytic degradation performance of BC@LDHs Z-scheme heterojunctions were fully explored from the perspectives of band structure and oxygen adsorption, determination of built-in electric field in Z-scheme heterojunctions, calculation of built-in electric field strength and bulk charge separation efficiency. This work proposes the insights that using Br doping to alter exposed facets and regulate the strength of the built-in electric field in Br-Cu2O@NiFe-LDHs heterojunctions, thereby promoting its efficient photocatalytic degradation.

Dual polarization for efficient III-nitride-based deep ultraviolet micro-LEDs

The deep ultraviolet (DUV) micro-light emitting diode (μLED) has serious electron leakage and low hole injection efficiency. Meanwhile, with the decrease in the size of the LED chip, the plasma-assisted dry etching process will cause damage to the side wall of the mesa, which will form a carrier leakage channel and produce non-radiative recombination. All of these will reduce the photoelectric performance of μLED. To this end, this study introduces polarized bulk charges into the hole supply layer (p-HSL) and the electron supply layer (n-ESL) respectively (dual-polarized structure) of the DUV μLED at an emission wavelength of 279 nm to enhance the binding of carriers and increase the injection efficiency of carriers. This is because the polarization-induced bulk charge can shield the polarized sheet charge on the interface and reduce the polarization electric field. The reduced polarization electric field in p-HSL can increase the effective barrier height of the conduction band in the p-type region and reduce the effective barrier height of the valence band. The decrease in the polarized electric field of n-HSL can reduce the thermal velocity of electrons, thereby enhancing the electron injection efficiency, reducing the Shockley–Read–Hall (SRH) recombination, and increasing the effective barrier height of the valence band. The study results indicate that the electron concentration and hole concentration of a μLED with dual polarization were increased by 77.93% and 93.6%, respectively. The optical power and maximum external quantum efficiency of μLED reached 31.04 W/cm2 and 2.91% respectively, and the efficiency droop is only 2.06% at 120 A/cm2. These results provide a new approach to solving the problem of insufficient carrier injection and SRH recombination in high-performance DUV μLEDs.

Analytical Model for Current-Voltage Characteristics in Perovskite Solar Cells Incorporating Bulk and Surface Recombination.

The effects of surface recombination on the steady-state carrier profiles and photocurrent in perovskite solar cells are investigated in this paper. The continuity equations for both holes and electrons are solved considering carrier drift and diffusion under the exponential carrier generation profile in the perovskite layer and considering both bulk and interface carrier recombination. An analytical expression for the solar-induced photocurrent is derived. The rate of carrier recombination at the interfaces has a very significant effect on the carrier profile, photocurrent, and, hence, on the charge collection efficiency. The external current density is calculated considering the dark current and nominal solar spectrum-induced photocurrent. The proposed model is fitted and verified with published experimental results from various publications. The fittings of the model with experimental results provide information about the interface and bulk charge carrier transport parameters.

Weak Hopf symmetry and tube algebra of the generalized multifusion string-net model

We investigate the multifusion generalization of string-net ground states and lattice Hamiltonians, delving into their associated weak Hopf symmetries. For the multifusion string-net, the gauge symmetry manifests as a general weak Hopf algebra, leading to a reducible vacuum string label; the charge symmetry, serving as a quantum double of gauge symmetry, constitutes a connected weak Hopf algebra. This implies that the associated topological phase retains its characterization by a unitary modular tensor category (UMTC). The bulk charge symmetry can also be captured by a weak Hopf tube algebra. We offer an explicit construction of the weak Hopf tube algebra structure and thoroughly discuss its properties. The gapped boundary and domain wall models are extensively discussed, with these 1d phases characterized by unitary multifusion categories (UMFCs). We delve into the gauge and charge symmetries of these 1d phases, as well as the construction of the boundary and domain wall tube algebras. Additionally, we illustrate that the domain wall tube algebra can be regarded as a cross product of two boundary tube algebras. As an application of our model, we elucidate how to interpret the defective string-net as a restricted multifusion string-net.

Effects of using nanosecond repetitively pulsed discharge and turbulent jet ignition on internal combustion engine performance

Robust ignition of hard-to-ignite fuels is essential for future spark ignited internal combustion engines, particularly for introducing efficiency-enhancing diesel-like process parameters like air excess or high amounts of exhaust gas recirculation (EGR). On the one hand, novel plasma-based ignition systems like Nanosecond Repetitively Pulsed Discharge (NRPD) are promising in extending the ignition limits and the early flame development speed. On the other hand, Turbulent Jet Ignition is effective for shortening the combustion duration and decreasing the unburned hydrocarbon emissions.This article investigates experimentally the combination of NRPD ignition and TJI. The aim is to use a technology for robust inflammation (NRPD) in combination with a technology for fast combustion of the bulk charge (TJI). For this purpose, a turbocharged light-duty four-cylinder engine operated with natural gas is used. The engine can be fitted with a classical Open Chamber (OC) spark plug or with Pre-Chambers (PC). The PCs can be filled uniquely with fuel and air coming from the Main Chamber (MC) (“passive PC”), or additional fuel can be added to the PCs (“active PC”). The air-to-fuel ratio and EGR rate can be freely controlled. Five different combustion strategies are investigated with NRPD ignition and compared against an inductive discharge ignition system. The combustion strategies are passive PC with air and EGR dilution, active PC with air dilution, and Open Chamber (OC) with air and EGR dilution. HRR evaluations and a loss analyses are performed to interpret the results.Despite the faster inflammation present with NRPD ignition, similar peak efficiencies and emissions are reached in OC configuration using the inductive discharge and NRPD ignition systems, which are achieved by varying air-to-fuel ratios (AFR) and EGR rates. Above dilution levels for peak efficiency, the efficiency using NRPD ignition decreases at a slower pace and tolerates higher AFR and EGR rates, thanks to a more complete and shorter combustion.For the PC experiments using NRPD ignition, an efficiency increases and a reduction of emissions compared to inductive discharge ignition are present for the investigated AFR and EGR rates for both active and passive PC operations. The efficiency increase is present due to a stronger pre-chamber discharge and thanks to a faster end phase of combustion. Actively fueling the PC results in faster and more complete combustion that is overcompensated by the increased wall heat losses, reducing the overall efficiency. The results show that passive PC with NRPD ignition may be an ideal ignition concept that maximizes engine efficiency and minimizes emissions.