Electron Storage Research Articles

Photochargeable Mn-Based Metal-Organic Framework and Decoupled Photocatalysis.

Designing multifunctional materials that mimic the light-dark decoupling of natural photosynthesis is a key challenge in the field of energy conversion. Herein, we introduce MnBr-253, a precious metal-free metal-organic framework (MOF) built on Al nodes, bipyridine linkers and MnBr(CO)3(bipyridine) complexes. Upon irradiation, MnBr-253 colloids demonstrate an electron photocharging capacity of ~42 C ⋅ g-1 MOF, with state-of-the-art photocharging rate (1.28 C ⋅ s-1 ⋅ g-1 MOF) and incident photon-to-electron conversion efficiency of ~9.4 % at 450 nm. Spectroscopic and computational studies support effective electron accumulation at the Mn complex while high porosity and Mn loading account for the notable electron storage performance. The charged MnBr-253 powders were successfully applied for hydrogen evolution under dark conditions thus emulating the light-decoupled reactivity of photosynthesis.

Metal-Semiconductor Heterojunction with Ohmic Contact Realizes Efficient Infrared-Light-Driven Photocatalysis.

Efficient utilization of solar energy for photocatalytic applications, particularly in the infrared spectrum, is crucial for addressing environmental challenges and energy scarcity. Herein we present a general strategy for constructing efficient infrared-driven photocatalysts in a metal/semiconductor heterojunction with Ohmic contact, where metals with low work function as the infrared-light absorber and semiconductors with electron storage ability can overcome the unfavorable electron flowback. Taking the NixB/MO2 (M = Ce, Ti, Sn, Ge, Zr, etc.) heterojunction as an example, both experimental and theoretical investigations reveal that the formation of an Ohmic contact facilitates the transfer of hot electrons from NixB to MO2, which are stored by the ion redox pairs for the variable valence character of M. As expected, the heterojunction exhibits remarkable photocatalytic activity under infrared light (λ ≥ 800 nm), as evidenced by the efficient photofixation of CO2 to high-value-added cyclic carbonates. This study offers a general platform for designing infrared-light-driven photocatalysts.

Enhanced hydrogen production performance via noble-metal-free amorphous NiZnSx-CS co-catalyst with novel gradient coating structure

In photocatalytic water splitting for hydrogen production, co-catalyst is a key factor in enhancing the efficiency of photocatalyst. Various inexpensive co-catalysts besides noble metal co-catalysts have been developed; however, the illumination of the relationship between the structure and performance remains a challenge. Here, we present a bimetallic sulfide co-catalyst denoted as NiZnSx-CS with amorphous and gradient coating structures to achieve highly efficient hydrogen production activity. Upon coupling the co-catalyst with CdS, the hydrogen production rate of CdS loaded with NiZnSx-CS reaches 38.0 mmol/g/h, 11.0, 40.0 and 161.0 times higher than that loaded with bulk NiZnSx, 1.0 %Pt and naked CdS, respectively. The co-catalyst with an amorphous and gradient coating structure shows large capacitance and thus facilitates efficient storage, transfer, and separation of photo-excited electrons of semiconductors, effectively reducing the over-potential of hydrogen production. The co-catalyst also has a large specific surface area and excellent hydrophilicity attributed to the abundant active sites and intimate contact with the reactant. Additionally, the coordination structure and chemical environment of NiZnSx-CS elucidated using X-ray absorption spectroscopy (XAS). The intermediates and the role of lactic acid and water on the surface of NiZnSx-CS after irradiation are determined by in situ Fourier transform infrared spectroscopy (in situ FT-IR). This work proposes a strategy to develop a highly efficient special structure co-catalyst with suitable capacitance, specific surface area and hydrophilicity.

Fe3O4/ZnO/L-lysine functionalized graphene oxide a promising nanocomposite with double Z-scheme visible photocatalytic and dark catalytic activity for water remediation

Developing multifunctional catalysts for efficient pollutant degradation in dark and visible light conditions represents a significant advancement in water remediation technology. This study reports the synthesis of a novel Fe3O4/ZnO/Lys-rGO nanocomposite via environmentally friendly methods that exhibit catalytic-photocatalytic activity for efficient degradation of organic pollutants. The synergistic effect of compositing Lys-rGO, a bio-organic component with a narrow band gap (1.08 eV), into the Fe3O4/ZnO inorganic composite induces a double Z-scheme mechanism by providing two pathways for effective charge separation in the visible photocatalytic activity of the nanocomposite. Additionally, the stored electrons in the very conductive Lys-rGO layers offer active sites for the catalytic activity of the nanocomposite in the dark. Meanwhile, ZnO generates reactive oxygen species (ROS) through surface oxygen vacancies, further contributing to the nanocomposite’s dark catalytic activity. The degradation of various organic pollutants (Methylene Blue, Tetracycline, Ciprofloxacin, Rhodamine B, and their mixture), as well as Congo Red, with low catalyst dosage and visible light irradiation time, demonstrates the high performance and versatility of this nanocomposite. This research highlights the potential of Lys-rGO in compositing with semiconductors to design multifunctional catalysts for cost-effective sustainable water purification technologies.

Carbon doping and bridging oxygen benefit for g-C3N4 to photocatalytic H2 production from methanol/water splitting: Experiments and theoretical calculations

Water-based homogeneous pre-assembly and thermal polycondensation were used to prepare carbon-doped oxygen-bridged layer-twisted graphite carbon nitride (g-C3N4) heterojunction for highly efficient photocatalytic hydrogen evolution (PHE). Despite the narrow band gap of around 0.91 eV, g-C3N4 heterojunction exhibited an excellent hydrogen evolution rate (563.87 μmolg−1h−1) in 30 % methanol/water solution without precious metal assisting catalysts, 36.85 times higher than g-C3N4. C doping in heptazine ring and bridging O caused the adjacent layer of g-C3N4 to twist by 11° in three-dimensional space. Noticeably, carbon doping in triazine ring was favorable to the establishment of build-in electric field between adjacent layers owing to the delocalized large π bonds. Bridging oxygen acted as a conversion switch for electron storage and transport of photogenerated charge from innerlayer (unmodified layer) with high Fermi level to outlayer (modified layer) with low Fermi level. This work provided an insightful guidance to novel layer-twisted g–C3N4–based photocatalysts for efficient H2 production.

Achieving a solar-to-chemical efficiency of 3.6% in ambient conditions by inhibiting interlayer charges transport

Efficiently converting solar energy into chemical energy remains a formidable challenge in artificial photosynthetic systems. To date, rarely has an artificial photosynthetic system operating in the open air surpassed the highest solar-to-biomass conversion efficiency (1%) observed in plants. In this study, we present a three-dimension polymeric photocatalyst achieving a solar-to-H2O2 conversion efficiency of 3.6% under ambient conditions, including real water, open air, and room temperature. The impressive performance is attributed to the efficient storage of electrons inside materials via expeditious intramolecular charge transfer, and the fast extraction of the stored electrons by O2 that can diffuse into the internal pores of the self-supporting three-dimensional material. This construction strategy suppresses the interlayer transfer of excitons, polarizers and carriers, effectively increases the utilization of internal excitons to 82%. This breakthrough provides a perspective to substantially enhance photocatalytic performance and bear substantial implications for sustainable energy generation and environmental remediation.

Superior AlGaN/GaN-Based Phototransistors and Arrays with Reconfigurable Triple-Mode Functionalities Enabled by Voltage-Programmed Two-DimensionalElectron Gas for High-Quality Imaging.

High-quality imaging units are indispensable in modern optoelectronic systems for accurate recognition and processing of optical information. To fulfill massive and complex imaging tasks in the digital age, devices with remarkable photoresponsive characteristics and versatile reconfigurable functions on a single-device platform are in demand but remain challenging to fabricate. Herein, an AlGaN/GaN-based double-heterostructure is reported, incorporated with a unique compositionally graded AlGaN structure to generate a channel of polarization-induced two-dimensional electron gas (2DEGs). Owing to the programmable feature of the 2DEGs by the combined gate and drain voltage inputs, with a particular capability of electron separation, collection and storage under different light illumination, the phototransistor shows reconfigurable multifunctional photoresponsive behaviors with superior characteristics. A self-powered mode with a responsivity over 100AW-1 and a photoconductive mode with a responsivity of ≈108AW-1 are achieved, with the ultimate demonstration of a 10×10 device array for imaging. More intriguingly, the device can be switched to photoelectric synapse mode, emulating synaptic functions to denoise the imaging process while prolonging the image storage ability. The demonstration of three-in-one operational characteristics in a single device offers a new path toward future integrated and multifunctional imaging units.

A novel approach of photo-charging and dark-discharging mechanisms by using V2O5 / g-C3N4 photocatalysts for ciprofloxacin degradation

Day and night photocatalysis offers a novel approach by integrating the electron storage principle to ensure effectiveness even in the absence of light. A groundbreaking vanadium pentoxide / graphitic carbon nitride (V2O5 / g-C3N4) composite photocatalyst functioned as g-C3N4 absorbs and utilizes visible light, while V2O5 transfers and stores more photo-generated electrons. The composite with a 2 % loading ratio showed the highest CIP removal efficiency: 91 % during daytime and 75 % at night. Successful nighttime degradation was due to stored electrons in V5+/ V4+ pairs, confirmed by XPS analysis of the reduction of V5+ to V4+. The study proposes detailed mechanisms for charge generation, reactive species action, and reactions during both day and night photocatalysis. This has significance for water treatment in real environmental settings with lower energy requirements, overcoming light-related limitations.

Intercalation of quaternary ammonium cations as a key factor of electron storage in MoS2 thin films

Electrochemical intercalation of cations within two-dimensional transition metal dichalcogenides presents a promising route for tailoring their optoelectronic properties. We have now succeeded in modulating the optical properties of MoS2 thin films through electrochemical intercalation of quaternary ammonium cations. The spectroelectrochemical experiments conducted with varying sizes of the intercalant revealed the size-dependent stability of the intercalated MoS2 nanosheets. The observed absorption change of the exciton bands is reversible and arises from the storage of electrons in MoS2 nanosheets and the subsequent weakening of interlayer van der Waals interactions following cation intercalation. This structural change is evidenced by the emergence of A*1g out-of-plane Raman mode. Additionally, the photoelectron spectroscopy reveals the emergence of a lower binding energy component of Mo 3d and the shift in Fermi level to higher energies, confirming the presence of stored electrons in cation intercalated-MoS2. The underlying mechanism of intercalation-induced property modifications in MoS2 discussed in the present study is useful in developing strategies for energy conversion devices.

Confirming the theoretical foundation of steady-state microbunching

Steady-State Microbunching (SSMB) has been proposed as a concept to generate coherent synchrotron radiation at an electron storage ring. SSMB promises to supply kilowatt level average power radiation in the extreme ultraviolet regime, meeting the power level demands for lithography applications that presently cannot be fulfilled by established accelerator technologies. SSMB is under theoretical and experimental study, building on a proof-of-principle (PoP) experiment at the Metrology Light Source which previously showed the viability of the idea. Here we report experimental findings from systematic studies in the ongoing SSMB PoP experiment, where microbunching is generated from an energy modulation imposed by a laser of wavelength 1064 nm. The results confirm the expected dependence of the microbunching process on modulation amplitude and show that the influence of transverse-longitudinal coupling dynamics is as predicted. This confirmation of key parts of the SSMB theory establishes a solid footing for continuing the proof-of-principle efforts towards the goal of constructing a prototype SSMB light source facility.

Polyoxometalate-based plasmonic electron sponge membrane for nanofluidic osmotic energy conversion.

Nanofluidic membranes have demonstrated great potential in harvesting osmotic energy. However, the output power densities are usually hampered by insufficient membrane permselectivity. Herein, we design a polyoxometalates (POMs)-based nanofluidic plasmonic electron sponge membrane (PESM) for highly efficient osmotic energy conversion. Under light irradiation, hot electrons are generated on Au NPs surface and then transferred and stored in POMs electron sponges, while hot holes are consumed by water. The stored hot electrons in POMs increase the charge density and hydrophilicity of PESM, resulting in significantly improved permselectivity for high-performance osmotic energy conversion. In addition, the unique ionic current rectification (ICR) property of the prepared nanofluidic PESM inhibits ion concentration polarization effectively, which could further improve its permselectivity. Under light with 500-fold NaCl gradient, the maximum output power density of the prepared PESM reaches 70.4 W m-2, which is further enhanced even to 102.1 W m-2 by changing the ligand to P5W30. This work highlights the crucial roles of plasmonic electron sponge for tailoring the surface charge, modulating ion transport dynamics, and improving the performance of nanofluidic osmotic energy conversion.

Covalent graft of Polypyridineruthenium(II) Complex-ZnTPP dyad with fullerol and immobilization onto TiO2 for enhanced photoassisted water oxidation activity

The covalent linkage of the light-harvester with the water oxidation catalyst is an effective way to construct heterogeneous catalysts with both light harvesting ability and catalytic oxygen evolution activity, and remains a challenge for simulated photosynthesis systems. Herein, two heterogeneous composite catalysts of ZnTPPtpyRubpyPHFTiO2 and ZnTPPtpyRubpyTiO2, with both the light harvesting capability and the catalytic water oxidation (CWE) performance, were successfully designed and prepared, and were fully characterized. Research indicated that the transfer mode of the photo-generated carrier for the two photo-assisted heterogeneous catalysts follows the type II mechanism, and the photo-generated holes promote the CWE activity. Compared to the dark condition (with TOF values of 42.3 and 41.8, respectively), ZnTPPtpyRubpyPHFTiO2 and ZnTPPtpyRubpyTiO2 exhibit superior CWE activity and efficiency in the illumination condition (with TOF values of 120 and 48.31, respectively). Fullerol, playing the role of an electron acceptor and an electron-pool, promotes charge separation and electron storage, which leads to a better suppression in charge recombination and enhancement in charge injection for ZnTPPtpyRubpyPHFTiO2. Therefore, ZnTPPtpyRubpyPHFTiO2 demonstrates a significantly improved catalytic activity in the illumination condition with a much higher TOF value compared to that of ZnTPPtpyRubpyTiO2.

Electron-parking engineering assisted ZnIn2S4/Mo2TiC2-Ru photocatalytic hydrogen evolution for efficient solar energy conversion and storage

The electron utilization efficiency in photocatalytic hydrogen evolution (PHE) is crucial for solar energy conversion and storage. Prolonged lifetime and effective use of accumulated electrons based on the storage-release behavior is a potential strategy to regulate the electronic utilization efficiency. Herein, this study utilized Mo2TiC2-Ru as the “electron-parking” to construct a ZnIn2S4/Mo2TiC2-Ru photocatalyst. The ZnIn2S4/Mo2TiC2-Ru exhibits a visible light-driven PHE rate of 5.72 mmol·g−1·h−1, and maintains a PHE rate of ∼1.67 mmol·g−1·h−1 under dark conditions. The photogenerated electrons could be directionally stored in Mo2TiC2-Ru to create an electron-rich environment, this can inhibit backflow and recombination of electrons, and could regulate the water dissociation and hydrogen adsorption kinetics. Importantly, the stored electrons could release in the dark, increasing the quantity of electrons and overcoming intermittent sunlight and regional environmental influences. This work provides insights and references for the development of capacitive cocatalysts with an “electron-parking” engineering for efficient and sustained PHE reactions.

Compact HOM-damping structure of a beam-accelerating TM020 mode rf cavity

A compact HOM-damping beam-accelerating rf cavity was developed to mitigate coupled-bunch instabilities in electron storage rings. This cavity operates in the TM020 mode, characterized by a high Q-value and a high shunt impedance. The new HOM-damping mechanism leverages the unique field distributions of the TM020 mode, allowing direct embedding of rf absorbing materials into the cavity body. This novel structure underwent validation through rf simulations and measurements using a model cavity resonating at 508.58 MHz in the TM020 mode with a shunt impedance of 6.8 MΩ and designed to have HOM impedances of less than 0.1 MΩ longitudinally and 0.5 MΩ/m transversely. We also fabricated and tested a prototype cavity, showcasing its HOM-damping efficacy and high-power functionality at 120 kW, generating an accelerating voltage of 900 kV. This prototype operated successfully at full power, confirming the viability of both the damping structure and its high-power application.

From Light to Dark: Dancing with Electrons in Colloidal 2D MoS2 Nanosheets.

Extending the lifetime of photogenerated electrons in semiconductor systems is an important criterion for the conversion of light into storable energy. We have now succeeded in storing electrons in a photoirradiated colloidal molybdenum disulfide (MoS2) suspension, showcasing its unique reversible photoresponsive behavior. The dampened A and B excitonic peaks indicate the accumulation of photogenerated electrons and the minimization of interactions between MoS2 interlayers. The stored electrons were quantitatively extracted by titrating with a ferrocenium ion in the dark, giving ca. 0.2 electrons per MoS2 formula unit. The emergence of the photoinduced A1g* Raman mode and the decrease in zeta potential after irradiation suggest intercalation of counterions to maintain overall charge balance upon electron storage. These results provide insights into the mechanism of photogenerated electron storage in 2D materials and pave the way for the potential application of colloidal 2D materials in electron storage.

Highly stable Ag-doped Cu2O immobilized cellulose-derived carbon beads with enhanced visible-light photocatalytic degradation of levofloxacin

Ag-doped Cu2O immobilized carbon beads (Ag/Cu2O@CB) based composite photocatalysts have been prepared for the removal of levofloxacin, an antibiotic, from water. The photocatalysts were prepared by the processes of chemical reduction and in-situ solid-phase precipitation. The composite photocatalyst was characterized by a porous and interconnected network structure. Ag nanoparticles were deposited on Cu2O particles to develop a metal-based semiconductor to increase the catalytic efficiency of the system and the separation efficiency of the photogenerated carriers. Cellulose-derived carbon beads (CBs) can also be used as electron storage libraries which can capture electrons released from the conduction band of Cu2O. The results revealed that the maximum catalytic degradation efficiency of the composite photocatalyst for the antibiotic levofloxacin was 99.02 %. The Langmuir–Hinshelwood model was used to study the reaction kinetics, and the process of photodegradation followed first-order kinetics. The maximum apparent rate was recorded to be 0.0906 min-1. The mass spectrometry technique showed that levofloxacin degraded into carbon dioxide and water in the presence of the photocatalyst. The results revealed that the easy-to-produce photocatalyst was stable and efficient in levofloxacin removing.

Carbon nitride interlayer-enhanced TiO2/WO3 nanorods with surface oxygen vacancies for durable photocathodic performance on 304 stainless steel in simulated seawater

To achieve a long-term photocathodic protective effect on metals in the marine environment, efficient charge mobility and electron storage are essential. Herein, we develop an oxygen vacancy (VO)-involved TiO2-wrapped WO3 nanorod composite by PPy-derived carbon nitride interlayer (TiO2/CNx/WO3) for the photoelectrochemical cathodic protection of 304SS in 3.5 % NaCl solution. The introduced CNx can serve not only as an electron channel to accelerate carrier migration but also as an efficient reductant to generate VO at the interfaces of TiO2 and WO3 during crystallization. The incorporated VO tunes the electronic structure and produces the mid-gap states, which lower the energy barrier for electron-hole separation. Meanwhile, WO3 nanorods as an electron self-storage pool make the photocathodic protection functional in darkness. Consequently, the as-prepared TiO2/CNx/WO3 photoanode yields a photocurrent density of 18.23 μA·cm−2 and a photoinduced cathodic polarization potential of −306 mV in simulated seawater. Even in the absence of light illustration, it can polarize 304SS to approximately −200 mV and continuously to 300 mV after 12h. This work will offer a universal strategy for the rational design and fabrication of highly efficient semiconductor composite materials in the field of photocathodic anticorrosion.

The Compton Energy Loss of Electrons in Storage Rings

We examine, in general, the energy loss of electrons caused by the Compton scattering of electrons on black body photons in the storage rings. We derive the scattering rate of electrons in the Planckian photon sea and then the energy loss of electrons per unit length. We discuss possible generalization of our method in particle physics and consider a possible application of our formulas in case of motion of charged particles in the relic cosmological radiation.

Revised Hamiltonian near third-integer resonance and implications for an electron storage ring

Revised Hamiltonian near third-integer resonance and implications for an electron storage ring

An ultrahigh hydrogen production rate of photocatalyst Fe2S2(CO)6/MoS2/CdS integrated mimic hydrogenase and capacitor for H2 evolution with longer lifetime of photoexcited electrons

The hydrogenase mimics provide an innovative strategy for photocatalytic hydrogen production; however, the efficiency mismatch between electron production and utilization results in low hydrogen production rate. Herein, we report the integration of non-noble metal cocatalyst MoS2 decorated with hydrogenase model complex Fe2S2(CO)6 and CdS QDs to assemble Fe2S2(CO)6/MoS2/CdS QDs, which exhibited an excellent hydrogen production rate of 10,836 μmol/g/h. This rate is 127.4, 9.1, and 1.6 times higher than that of CdS QDs, Fe2S2(CO)6/CdS QDs, and MoS2/CdS QDs, respectively. In comparison to CdS or MoS2/CdS, transient photovoltage (TPV) measurements revealed that the photovoltage response of Fe2S2(CO)6/MoS2/CdS increased numerically by 3.3 times; meanwhile, Fe2S2(CO)6/MoS2/CdS significantly extended the lifetime of photo-generated electrons. The excellent performance was attributed to the distinct capacitance effect and functional active site of Fe2S2(CO)6/MoS2/CdS, which boosted electron storage and redistribution at the interface to alleviate recombination losses and facilitate hydrogen production.