The main “bottleneck” limiting the beam power in circular machines is caused by space charge effects that produce beam instabilities. To increase maximally the beam power of a “proton driver”, it is proposed to bu...The main “bottleneck” limiting the beam power in circular machines is caused by space charge effects that produce beam instabilities. To increase maximally the beam power of a “proton driver”, it is proposed to build a facility consisting solely of a 2.5 GeV injector linac (PI) and a 20 GeV pulsed superconducting linac (SCL). Such a facility could be constructed using the existing KEK accelerator infrastructure. The PI, based on the European Spallation Source (ESS) linac, would serve both as an injector to the SCL and a source of proton beams that could be used to copiously produce, e.g., muons and “cold” neutrons. Protons accelerated by the SCL would be transferred through the KEK Tristan ring in order to create neutrino, kaon and muon beams for fixed-target experiments. At a later stage, a 70 GeV proton synchrotron could be installed inside the Tristan ring. The SCL, comprising 1.3 GHz ILC-type rf cavities, could also accelerate polarized or unpolarized electron beams. After acceleration, electrons could be used to produce polarized positrons, or may traverse an XFEL undulator.展开更多
The Standard Model of particle physics assumes that fundamental fermions are point particles with zero radius, no spatial dimensions, and infinite matter density. This alternative model treats the nine charged fundame...The Standard Model of particle physics assumes that fundamental fermions are point particles with zero radius, no spatial dimensions, and infinite matter density. This alternative model treats the nine charged fundamental fermions (three leptons and nine quarks) as spheres with non-zero holographic radius. Holographic analysis (based on quantum mechanics, general relativity, thermodynamics, and Shannon information theory) specifies electron mass by five fundamental constants: Planck’s constant ℏ, gravitational constant G, fine structure constant α, cosmological constant Λ, and vacuum energy fraction ΩΛ. Protons and neutrons are composite systems of up and down quarks. Describing forces between quark constituents confined within nucleons as inverse square attractive forces, this alternative model identifies composition factors Cpand Cnto relate proton and neutron masses to electron mass and thus to fundamental constants. An appendix summarizes holographic analyses characterizing astronomical masses at the opposite end of the mass scale for objects in the universe.展开更多
Graphene encapsulation has been shown to be an effective technique for improving the corrosion resistance of non-noble metal catalysts for the acidic water electrolysis.The key challenge lies in enhancing the electroc...Graphene encapsulation has been shown to be an effective technique for improving the corrosion resistance of non-noble metal catalysts for the acidic water electrolysis.The key challenge lies in enhancing the electrocatalytic activity of graphene-encapsulated metals while maintaining their durability in acidic media.Herein,an electron-transfer-tuning strategy is investigated at the graphene/NiMo interface,aiming to improve the hydrogen evolution reaction(HER)performance of graphene-encapsulated NiMo catalysts.The doping of Ti,a low electronegativity element,into NiMo substrate was confirmed to increase electron transfer from the metal core toward the graphene.The electron-rich state on graphene facilitates the adsorption of positively charged protons on graphene,thereby enabling a Pt/C-comparable performance in 0.5 M H_(2)SO_(4),with only a 3.8%degradation in performance over a 120-h continuous test.The proton exchange membrane(PEM)water electrolyzer assembled by the N-doped grapheneencapsulated Ti-doped NiMo exhibits a smaller cell voltage to achieve a current density of 2.0 A cm^(-2),in comparison to the Pt/C based counterpart.This study proposes a novel electron-transfer-tuning strategy to improve the HER activity of graphene-encapsulated non-noble metal catalysts without sacrificing durability in acidic electrolytes.展开更多
The limited activity of atomically-dispersed M-N-C electrocatalysts severely restricts their applicability in the oxygen reduction reaction(ORR)for proton exchange membrane fuel cells(PEMFC).Herein,we design and synth...The limited activity of atomically-dispersed M-N-C electrocatalysts severely restricts their applicability in the oxygen reduction reaction(ORR)for proton exchange membrane fuel cells(PEMFC).Herein,we design and synthesize Se-doped Fe-N-C hierarchical porous electrocatalyst(FeN_(4)/SeC_(2))by optimizing carbon structure and FeN_(4)coordination environment.The FeN_(4)/SeC_(2)electrocatalyst exhibits outstanding ORR activity in 0.1 mol L^(-1)HClO_(4),and the resulting PEMFC presents a peak power density of 1.20 W cm^(-2)in H_(2)-O_(2)condition at a back pressure of 200 kPa,ranking in the top levels among most reported non-precious metal catalyst-based fuel cells.The lower O_(2)transfer resistance of FeN_(4)/SeC_(2)-based membrane electrode assembly than FeN_(4)-based one means faster O_(2)transport in triple-phase boundary(TPB),and Density functional theory calculation further reveals that the synergistic catalysis between porous SeC_(2)and FeN_(4)-OH species can efficiently lower the energy barriers for the rate-determining step of the ORR.In short,the outstanding performance of FeN_(4)/SeC_(2)in PEMFC is ascribed to the Se-doping,which introduces more defects and larger mesoporosity and therefore facilitates ionomer infiltration and O_(2)transfer and charge transfer in TPB.The effective strategy of enhancing mass and charge transfers in TPB is anticipated to be applicable in the construction of highly efficient ORR electrocatalysts.展开更多
Electron transfer processes at polymer electrolyte/electrode interfaces play a central role in modern electrochemical devices of energy conversion,however,current understanding of electron transfers through electroche...Electron transfer processes at polymer electrolyte/electrode interfaces play a central role in modern electrochemical devices of energy conversion,however,current understanding of electron transfers through electrochemical interfaces was established exclusively based on the studies of liquid/solid electrochemical interfaces.Thus,similarities and differences of liquid and polymer electrolyte/electrode interfaces need to be mapped out to guide the design of device level electrochemical interfaces.In this work,we employ the sulfonate adsorption/desorption as a probe reaction to understand the electron-transfer steps in polymer and liquid electrolytes.Through cyclic voltametric investigations on the well-define single-crystal Pd_(ML)Pt(111)electrode,we demonstrate that the oxidative adsorption and reductive desorption of sulfonates at the polymer electrolyte/electrode interface are chemically distinct from those in liquid electrolytes,with the former occurring mostly via the proton-coupled pathway while the latter proceeding mainly through the solvation-mediated pathway.Importantly,the sulfonate adsorption/desorption behaviors of alkylsulfonates become increasingly similar to those in Nafion with longer alkyl chains,suggesting that the interfacial hydrophobicity and solvation environment conferred by the perfluorinated polymer play a decisive role in the electron-transfer mechanism.Results reported in this study highlight the mechanistic distinctions between electron-transfer processes at electrochemical interfaces involving polymer and liquid electrolytes,and provide a framework for understanding electron-transfer processes at polymer electrolyte/electrode interfaces.展开更多
Understanding the degradation phenomenon of proton exchange membrane fuel cells under electrochemical cycling requires an analysis of the porous carbon support structure.Key factors contributing to this phenomenon inc...Understanding the degradation phenomenon of proton exchange membrane fuel cells under electrochemical cycling requires an analysis of the porous carbon support structure.Key factors contributing to this phenomenon include changes in the total porosity and viable surface area for electrochemical reactions.Electron tomography-based serial section imaging using focused ion beam-scanning electron microscopy(FIB-SEM)can elucidate this phenomenon at a nanoscale resolution.However,this highresolution tomographic analysis requires a huge image dataset and manual inputs in rule-based workflows;these requirements are time-consuming and often cause experimental difficulties and unreliable interpretations.We propose a deep learning-empowered approach comprising a two-step automated process for image interpolation and semantic segmentation to address the practical issues encountered in FIB-SEM electron tomography.An optimally trained interpolation model can reduce the image data requirement by more than 95%to analyze the structural degradation of carbon supports after electrochemical cycling while maintaining the reliability obtained in conventional tomographic analysis with several hundred images.Because the subsequent image segmentation model excludes a complicated manual filtering process,the relevant structural parameters can be reliably measured without human bias.Our sparse-section imaging-based deep learning process can allow cost-efficient analysis and reliable measurement of the degree of cycling-induced carbon corrosion.展开更多
Pyridyl-based ketones and 1,6-diketones are both attractive and invaluable scaffolds which play pivotal roles in the construction and structural modification of a plethora of synthetically paramount natural products,p...Pyridyl-based ketones and 1,6-diketones are both attractive and invaluable scaffolds which play pivotal roles in the construction and structural modification of a plethora of synthetically paramount natural products,pharmaceuticals,organic materials and fine chemicals.In this context,we herein demonstrate an unprecedented,robust and generally applicable synthetically strategy to deliver these two crucial ketone frameworks via visible-light-induced ring-opening coupling reactions of cycloalcohols with vinylazaarenes and enones,respectively.A plausible mechanism involves the selectiveβ-C-C bond cleavage of cycloalcohols enabled by proton-coupled electron transfer and ensuing Giese-type addition followed by single electron reduction and protonation.The synthetic methodology exhibits broad substrate scope,excellent functional group compatibility as well as operational simplicity and environmental friendliness.展开更多
Optimizing the microdynamics in alkaline and neutral conditions is a significant but challenging task in developing pH-universal hydrogen evolution(HER)electrocatalysts.Herein,a unique Pt-O-Ni bridge has been construc...Optimizing the microdynamics in alkaline and neutral conditions is a significant but challenging task in developing pH-universal hydrogen evolution(HER)electrocatalysts.Herein,a unique Pt-O-Ni bridge has been constructed to alter the coordination and electronic environment between Pt nanoparticles(Pt_n)and nickel metaphosphate(NPO)substrate(Pt-NPO).Sufficient electron transfer from NPO to Pt_n to maintain an electron-rich environment and a low valence state of Pt_n.Furthermore,H*is produced from the H_(2)O dissociation on Ni site and then spillover toward Pt sites to bind into H_(2),which makes up for the insufficient H_(2)O dissociation ability of Pt in Volmer step.Pt-NPO exhibits long-term stability and only need the overpotentials of 22.3,33.0 and 30.5 mV to attain 10 mA cm^(-2)in alkaline,neutral and acidic media,respectively.The anion-exchange membrane(AEM)water electrolyzer catalyzed by Pt-NPO shows high water electrolysis performance that a cell voltage of 1.73 V is needed to obtain the current density of500 mA cm^(-2)in 1 M KOH at 80℃,at the same time maintains good stability for 350 h.The regulation strategy proposed in this work is helpful for the design and synthesis of highly efficient pH-universal HER electrocatalysts.展开更多
We successfully incorporated phenyl groups into a small-molecule quaternary ammonium cross-linker and synthesized cross-linked polybenzimidazole membranes via a one-step cross-linking process.Compared with conventiona...We successfully incorporated phenyl groups into a small-molecule quaternary ammonium cross-linker and synthesized cross-linked polybenzimidazole membranes via a one-step cross-linking process.Compared with conventional quaternary ammonium-crosslinked benzimidazole membranes,the introduction of phenyl groups significantly increases the free volume within the membrane.After phosphoric acid doping,the benzimidazole membrane with larger free volume retains more phosphoric acid compared to conventional quaternary ammonium-crosslinked membranes,forming an extensive hydrogen-bonding network that effectively enhances its anhydrous proton conductivity.The anhydrous proton conductivity reaches 91 mS·cm^(-1)at 160℃,substantially higher than that of conventional quaternary ammonium-crosslinked membranes with the same mass fraction.Benefiting from the improved conductivity,the membrane electrode assembly exhibits reduced ohmic polarization,achieving a peak power density of 792 mW·cm^(-2)at 160℃.展开更多
Proton exchange membranes(PEMs)play a central role in determining the efficiency,durability,and operational flexibility of PEM fuel cells(PEMFCs).However,conventional PEMs exhibit strong temperature-dependent proton-t...Proton exchange membranes(PEMs)play a central role in determining the efficiency,durability,and operational flexibility of PEM fuel cells(PEMFCs).However,conventional PEMs exhibit strong temperature-dependent proton-transport behavior,which limits their ability to support both rapid start-up at low temperatures and stable operation at elevated temperatures.Water-mediated PEMs show excellent conductivity under low-temperature and high-humidity conditions but suffer from dehydration and structural instability in the high-temperature regime.In contrast,water-independent PEMs,particularly phosphoric-acid-doped systems,conduct protons efficiently under anhydrous high-temperature conditions yet experience acid leaching that hampers room-temperature start-up and long-term durability.This review summarizes the fundamental proton-transport mechanisms that govern temperature-dependent performance and discusses recent advances in materials design aimed at enabling wide-temperature-range PEM operation.For water-mediated membranes,strategies such as incorporating hydrophilic fillers,constructing confined hydrophilic domains,and introducing additional proton-transfer sites have been developed to mitigate water loss and stabilize proton conduction.For water-independent membranes,approaches including strengthening polymer–acid interactions,engineering nanoscale confinement,designing multilayer architectures,and constructing multi–proton-carrier networks effectively improve acid retention and broaden operational temperature windows.Emerging fixed-carrier systems based on phosphonic-acid-grafted polymers,metal–organic frameworks,and covalent organic frameworks offer new pathways for stable anhydrous proton conduction across a wide temperature range.We conclude by outlining key challenges and future research opportunities,including reducing the dependence on volatile or leachable proton carriers,developing adaptive nanochannel architectures,improving anhydrous high-temperature conduction,and establishing scalable membrane fabrication methods.Continued innovation in these directions is expected to enable next-generation wide-temperature-range PEMs capable of flexible,high-efficiency operation from sub-zero to high-temperature conditions.展开更多
Stretchable electronics have been recognized as intriguing next-generation electronics that possess huge market value,and stretchable electronic conductors(SECs)are essential for stretchable electronics,which not only...Stretchable electronics have been recognized as intriguing next-generation electronics that possess huge market value,and stretchable electronic conductors(SECs)are essential for stretchable electronics,which not only can serve as critical functional components but also are the indispensable electronic connections bridging various electronic components within stretchable electronic systems.Herein,we offer a comprehensive review of recent progress in SECs including the material categories,structure designs,fabrication techniques,and applications.The characteristics,performance enhancement strategies,and application requirements are emphasized.Based on the recent advances,the existing challenges and future prospects are outlined and discussed.展开更多
Covalent organic framework ionomers enable synergistic efficient transport of protons and oxygen in medium-temperature proton exchange membrane fuel cells Proton exchange membrane fuel cells(PEMFCs),as clean and effic...Covalent organic framework ionomers enable synergistic efficient transport of protons and oxygen in medium-temperature proton exchange membrane fuel cells Proton exchange membrane fuel cells(PEMFCs),as clean and efficient energy technologies,are constrained in their performance enhancement by the sluggish oxygen reduction reaction(ORR)kinetics at the cathode,anode CO poisoning(e.g.,from methanol crossover)and intricate water management dilemmas[1].展开更多
Permeable electronics promise improved physiological comfort,but remain constrained by limited functional integration and poor mechanical robustness.Here,we report a three-dimensional(3D)permeable electronic system th...Permeable electronics promise improved physiological comfort,but remain constrained by limited functional integration and poor mechanical robustness.Here,we report a three-dimensional(3D)permeable electronic system that overcomes these challenges by combining electrospun SEBS nanofiber mats,high-resolution liquid metal conductors patterned via thermal imprinting(50μm),and a strain isolators(SIL)that protects vertical interconnects(VIAs)from stress concentration.This architecture achieves ultrahigh air permeability(>5.09 m L cm^(-2)min^(-1)),exceptional stretchability(750%fracture strain),and reliable conductivity maintained through more than 32,500 strain cycles.Leveraging these advances,we have integrated multilayer circuits,strain sensors,and a three-axis accelerometer to achieve a fully integrated,stretchable,permeable wireless real-time gesture recognition glove.The system enables accurate sign language interpretation(98%)and seamless robotic hand control,demonstrating its potential for assistive technologies.By uniting comfort,durability,and high-density integration,this work establishes a versatile platform for nextgeneration wearable electronics and interactive human-robot interfaces.展开更多
This work presents a systematic analysis of proton-induced total ionizing dose(TID)effects in 1.2 k V silicon carbide(SiC)power devices with various edge termination structures.Three edge terminations including ring-a...This work presents a systematic analysis of proton-induced total ionizing dose(TID)effects in 1.2 k V silicon carbide(SiC)power devices with various edge termination structures.Three edge terminations including ring-assisted junction termination extension(RA-JTE),multiple floating zone JTE(MFZ-JTE),and field limiting rings(FLR)were fabricated and irradiated with45 Me V protons at fluences ranging from 1×10^(12) to 1×10^(14) cm^(-2).Experimental results,supported by TCAD simulations,show that the RA-JTE structure maintained stable breakdown performance with less than 1%variation due to its effective electric field redistribution by multiple P+rings.In contrast,MFZ-JTE and FLR exhibit breakdown voltage shifts of 6.1%and 15.2%,respectively,under the highest fluence.These results demonstrate the superior radiation tolerance of the RA-JTE structure under TID conditions and provide practical design guidance for radiation-hardened Si C power devices in space and other highradiation environments.展开更多
The effects of initial spin orientation on the final electron beam polarization in laser wakefield acceleration in a pre-polarized plasma are investigated theoretically and numerically.From the results of variation of...The effects of initial spin orientation on the final electron beam polarization in laser wakefield acceleration in a pre-polarized plasma are investigated theoretically and numerically.From the results of variation of the initial spin direction,the spin dynamics of the electron beam are found to depend on the self-injection mechanism.The effects of wakefields and laser fields are studied using test particle dynamics and particle-in-cell simulations based on the Thomas-Bargmann-Michel-Telegdi equation.Compared with transverse injection,longitudinal injection is found to be preferable for obtaining a highly polarized electron beam.展开更多
Electrochemical CO_(2) reduction reaction(CO_(2)RR) into valuable formate provides a strategy for carbon neutrality.Bismuth(Bi) catalysts,attributed to their appropriate energy barrier of OCHO*intermediate,have demons...Electrochemical CO_(2) reduction reaction(CO_(2)RR) into valuable formate provides a strategy for carbon neutrality.Bismuth(Bi) catalysts,attributed to their appropriate energy barrier of OCHO*intermediate,have demonstrated substantial potential for the advancement of electrocatalytic CO_(2) reduction to formate.However,due to the weak bonding of protons(H^(*)) of Bi,the available protonate of CO_(2) on Bi is insufficient,which limits the formation of OCHO^(*).Prediction by theoretical calculation,chlorine doping can effectively promote the dissociation of H_(2)O and thus achieve effective proton supply.We prepare chlorine-doped Bi(Cl-Bi) via an electrochemical conversion strategy for electroreduction of CO_(2) .An obvious improvement of faradaic efficiency(FE) of formate(96.7% at-0.95 V vs.RHE) can be achieved on Cl-Bi,higher than that of Bi(89.4%).Meanwhile,Cl-Bi has the highest formate production rate of 275 μmol h^(-1)cm^(-2)at-0.95 V vs.RHE,which is 1.2 times higher than that of Bi(224 μmol h^(-1)cm^(-2)).In situ characterizations and kinetic analysis reveal that chlorine doping promotes the activation of H_(2)O and supply sufficient protons to promote the protonation of CO_(2) to OCHO^(*),which is consistent with theoretical calculation.The study presents an effective strategy for rational design of highly efficient electrocatalysts to promote green chemical production.展开更多
The rapid advancement of machine learning based tight-binding Hamiltonian(MLTB)methods has opened new avenues for efficient and accurate electronic structure simulations,particularly in large-scale systems and long-ti...The rapid advancement of machine learning based tight-binding Hamiltonian(MLTB)methods has opened new avenues for efficient and accurate electronic structure simulations,particularly in large-scale systems and long-time scenarios.This review begins with a concise overview of traditional tight-binding(TB)models,including both(semi-)empirical and first-principles approaches,establishing the foundation for understanding MLTB developments.We then present a systematic classification of existing MLTB methodologies,grouped into two major categories:direct prediction of TB Hamiltonian elements and inference of empirical parameters.A comparative analysis with other ML-based electronic structure models is also provided,highlighting the advancement of MLTB approaches.Finally,we explore the emerging MLTB application ecosystem,highlighting how the integration of MLTB models with a diverse suite of post-processing tools from linear-scaling solvers to quantum transport frameworks and molecular dynamics interfaces is essential for tackling complex scientific problems across different domains.The continued advancement of this integrated paradigm promises to accelerate materials discovery and open new frontiers in the predictive simulation of complex quantum phenomena.展开更多
Traditional digitizers for signal readout of PET detectors are based on commercial analog-to-digital converters(ADC).However,the cost and power consumption of an entire electronic readout system based on digitizers fo...Traditional digitizers for signal readout of PET detectors are based on commercial analog-to-digital converters(ADC).However,the cost and power consumption of an entire electronic readout system based on digitizers for a PET scanner are high.To address this problem,a soft-core ADC based on a field-programmable gate array(FPGA)was proposed.An FPGA-based ADC(FPGA-ADC)combines low loss and high performance.To achieve good performance,the FPGA-ADC requires three calibrations:time-to-digital converter(TDC)length calibration,TDC alignment calibration,and TDC-to-ADC calibration.A prototype front-end electronics based on FPGA-ADC was built to evaluate the performance of time-of-flight positron emission tomography(TOF PET)detectors.Each PET detector consists of a LYSO crystal single-ended coupled to a silicon photomultiplier(SiPM).The experimental results show that the full-width at half-maximum(FWHM)energy resolution for 511 keV gamma photons after saturation correction of the SiPM was 12.3%.The FWHM coincidence timing resolution(CTR)of the TOF PET detector with the readout of the front-end electronic prototype is 385.2 ps.FPGA-ADCbased front-end electronics are very promising for multichannel,low-cost,highly integrated,and power-efficient readout electronic systems for radiation detector applications.展开更多
文摘The main “bottleneck” limiting the beam power in circular machines is caused by space charge effects that produce beam instabilities. To increase maximally the beam power of a “proton driver”, it is proposed to build a facility consisting solely of a 2.5 GeV injector linac (PI) and a 20 GeV pulsed superconducting linac (SCL). Such a facility could be constructed using the existing KEK accelerator infrastructure. The PI, based on the European Spallation Source (ESS) linac, would serve both as an injector to the SCL and a source of proton beams that could be used to copiously produce, e.g., muons and “cold” neutrons. Protons accelerated by the SCL would be transferred through the KEK Tristan ring in order to create neutrino, kaon and muon beams for fixed-target experiments. At a later stage, a 70 GeV proton synchrotron could be installed inside the Tristan ring. The SCL, comprising 1.3 GHz ILC-type rf cavities, could also accelerate polarized or unpolarized electron beams. After acceleration, electrons could be used to produce polarized positrons, or may traverse an XFEL undulator.
文摘The Standard Model of particle physics assumes that fundamental fermions are point particles with zero radius, no spatial dimensions, and infinite matter density. This alternative model treats the nine charged fundamental fermions (three leptons and nine quarks) as spheres with non-zero holographic radius. Holographic analysis (based on quantum mechanics, general relativity, thermodynamics, and Shannon information theory) specifies electron mass by five fundamental constants: Planck’s constant ℏ, gravitational constant G, fine structure constant α, cosmological constant Λ, and vacuum energy fraction ΩΛ. Protons and neutrons are composite systems of up and down quarks. Describing forces between quark constituents confined within nucleons as inverse square attractive forces, this alternative model identifies composition factors Cpand Cnto relate proton and neutron masses to electron mass and thus to fundamental constants. An appendix summarizes holographic analyses characterizing astronomical masses at the opposite end of the mass scale for objects in the universe.
基金supported by the National Natural Science Foundation of China(52302039,52301043)the Guangdong Basic and Applied Basic Research Foundation(2022A1515110676)+2 种基金the Shenzhen Science and Technology Program(JCYJ20220531095404009,RCBS20221008093057027,GXWD20231129113217001)the Postdoctoral Research Startup Expenses of Shenzhen(NA25501001)the Shenzhen Introduce High-Level Talents and Scientific Research Start-up Founds(NA11409005)。
文摘Graphene encapsulation has been shown to be an effective technique for improving the corrosion resistance of non-noble metal catalysts for the acidic water electrolysis.The key challenge lies in enhancing the electrocatalytic activity of graphene-encapsulated metals while maintaining their durability in acidic media.Herein,an electron-transfer-tuning strategy is investigated at the graphene/NiMo interface,aiming to improve the hydrogen evolution reaction(HER)performance of graphene-encapsulated NiMo catalysts.The doping of Ti,a low electronegativity element,into NiMo substrate was confirmed to increase electron transfer from the metal core toward the graphene.The electron-rich state on graphene facilitates the adsorption of positively charged protons on graphene,thereby enabling a Pt/C-comparable performance in 0.5 M H_(2)SO_(4),with only a 3.8%degradation in performance over a 120-h continuous test.The proton exchange membrane(PEM)water electrolyzer assembled by the N-doped grapheneencapsulated Ti-doped NiMo exhibits a smaller cell voltage to achieve a current density of 2.0 A cm^(-2),in comparison to the Pt/C based counterpart.This study proposes a novel electron-transfer-tuning strategy to improve the HER activity of graphene-encapsulated non-noble metal catalysts without sacrificing durability in acidic electrolytes.
文摘The limited activity of atomically-dispersed M-N-C electrocatalysts severely restricts their applicability in the oxygen reduction reaction(ORR)for proton exchange membrane fuel cells(PEMFC).Herein,we design and synthesize Se-doped Fe-N-C hierarchical porous electrocatalyst(FeN_(4)/SeC_(2))by optimizing carbon structure and FeN_(4)coordination environment.The FeN_(4)/SeC_(2)electrocatalyst exhibits outstanding ORR activity in 0.1 mol L^(-1)HClO_(4),and the resulting PEMFC presents a peak power density of 1.20 W cm^(-2)in H_(2)-O_(2)condition at a back pressure of 200 kPa,ranking in the top levels among most reported non-precious metal catalyst-based fuel cells.The lower O_(2)transfer resistance of FeN_(4)/SeC_(2)-based membrane electrode assembly than FeN_(4)-based one means faster O_(2)transport in triple-phase boundary(TPB),and Density functional theory calculation further reveals that the synergistic catalysis between porous SeC_(2)and FeN_(4)-OH species can efficiently lower the energy barriers for the rate-determining step of the ORR.In short,the outstanding performance of FeN_(4)/SeC_(2)in PEMFC is ascribed to the Se-doping,which introduces more defects and larger mesoporosity and therefore facilitates ionomer infiltration and O_(2)transfer and charge transfer in TPB.The effective strategy of enhancing mass and charge transfers in TPB is anticipated to be applicable in the construction of highly efficient ORR electrocatalysts.
基金supported by the National Key R&D Program of China(No.2021YFA1501003)。
文摘Electron transfer processes at polymer electrolyte/electrode interfaces play a central role in modern electrochemical devices of energy conversion,however,current understanding of electron transfers through electrochemical interfaces was established exclusively based on the studies of liquid/solid electrochemical interfaces.Thus,similarities and differences of liquid and polymer electrolyte/electrode interfaces need to be mapped out to guide the design of device level electrochemical interfaces.In this work,we employ the sulfonate adsorption/desorption as a probe reaction to understand the electron-transfer steps in polymer and liquid electrolytes.Through cyclic voltametric investigations on the well-define single-crystal Pd_(ML)Pt(111)electrode,we demonstrate that the oxidative adsorption and reductive desorption of sulfonates at the polymer electrolyte/electrode interface are chemically distinct from those in liquid electrolytes,with the former occurring mostly via the proton-coupled pathway while the latter proceeding mainly through the solvation-mediated pathway.Importantly,the sulfonate adsorption/desorption behaviors of alkylsulfonates become increasingly similar to those in Nafion with longer alkyl chains,suggesting that the interfacial hydrophobicity and solvation environment conferred by the perfluorinated polymer play a decisive role in the electron-transfer mechanism.Results reported in this study highlight the mechanistic distinctions between electron-transfer processes at electrochemical interfaces involving polymer and liquid electrolytes,and provide a framework for understanding electron-transfer processes at polymer electrolyte/electrode interfaces.
基金supported by the Technology Innovation Program(No.20011712)funded by the Ministry of Trade,Industry,and Energy(MOTIE,Korea)a National Research Foundation of Korea(NRF)grant funded by the Ministry of Science and ICT(MSIT)(No.2022M3J1A108538),Korea+2 种基金the support of the Nano&Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(RS-2024-00444986,50%)the Institute for Basic Science(IBS-R036-D1)。
文摘Understanding the degradation phenomenon of proton exchange membrane fuel cells under electrochemical cycling requires an analysis of the porous carbon support structure.Key factors contributing to this phenomenon include changes in the total porosity and viable surface area for electrochemical reactions.Electron tomography-based serial section imaging using focused ion beam-scanning electron microscopy(FIB-SEM)can elucidate this phenomenon at a nanoscale resolution.However,this highresolution tomographic analysis requires a huge image dataset and manual inputs in rule-based workflows;these requirements are time-consuming and often cause experimental difficulties and unreliable interpretations.We propose a deep learning-empowered approach comprising a two-step automated process for image interpolation and semantic segmentation to address the practical issues encountered in FIB-SEM electron tomography.An optimally trained interpolation model can reduce the image data requirement by more than 95%to analyze the structural degradation of carbon supports after electrochemical cycling while maintaining the reliability obtained in conventional tomographic analysis with several hundred images.Because the subsequent image segmentation model excludes a complicated manual filtering process,the relevant structural parameters can be reliably measured without human bias.Our sparse-section imaging-based deep learning process can allow cost-efficient analysis and reliable measurement of the degree of cycling-induced carbon corrosion.
基金financial support from National Natural Science Foundation of China(Nos.21801129,22078153 and22378201)National Key Research and Development Program of China(No.2022YFB3805603)+3 种基金Natural science research projects in Jiangsu Higher Education Institutions(No.18KJB150018)Open Research Fund of School of Chemistry and Chemical EngineeringHenan Normal University(No.2024Y16)Nanjing Tech University(Start-up Grant Nos.39837137,39837101 and 3827401739)for financial support。
文摘Pyridyl-based ketones and 1,6-diketones are both attractive and invaluable scaffolds which play pivotal roles in the construction and structural modification of a plethora of synthetically paramount natural products,pharmaceuticals,organic materials and fine chemicals.In this context,we herein demonstrate an unprecedented,robust and generally applicable synthetically strategy to deliver these two crucial ketone frameworks via visible-light-induced ring-opening coupling reactions of cycloalcohols with vinylazaarenes and enones,respectively.A plausible mechanism involves the selectiveβ-C-C bond cleavage of cycloalcohols enabled by proton-coupled electron transfer and ensuing Giese-type addition followed by single electron reduction and protonation.The synthetic methodology exhibits broad substrate scope,excellent functional group compatibility as well as operational simplicity and environmental friendliness.
基金supported by the National Natural Science Foundation of China(22202080,22034006 and 22393930)Jilin Talent Development Foundation(E41S2001)the National Key Research and Development Program of China(2022YFF0710000).
文摘Optimizing the microdynamics in alkaline and neutral conditions is a significant but challenging task in developing pH-universal hydrogen evolution(HER)electrocatalysts.Herein,a unique Pt-O-Ni bridge has been constructed to alter the coordination and electronic environment between Pt nanoparticles(Pt_n)and nickel metaphosphate(NPO)substrate(Pt-NPO).Sufficient electron transfer from NPO to Pt_n to maintain an electron-rich environment and a low valence state of Pt_n.Furthermore,H*is produced from the H_(2)O dissociation on Ni site and then spillover toward Pt sites to bind into H_(2),which makes up for the insufficient H_(2)O dissociation ability of Pt in Volmer step.Pt-NPO exhibits long-term stability and only need the overpotentials of 22.3,33.0 and 30.5 mV to attain 10 mA cm^(-2)in alkaline,neutral and acidic media,respectively.The anion-exchange membrane(AEM)water electrolyzer catalyzed by Pt-NPO shows high water electrolysis performance that a cell voltage of 1.73 V is needed to obtain the current density of500 mA cm^(-2)in 1 M KOH at 80℃,at the same time maintains good stability for 350 h.The regulation strategy proposed in this work is helpful for the design and synthesis of highly efficient pH-universal HER electrocatalysts.
基金Funded in part by the National Key Research and Development Program of China(No.2023YFB4006302)。
文摘We successfully incorporated phenyl groups into a small-molecule quaternary ammonium cross-linker and synthesized cross-linked polybenzimidazole membranes via a one-step cross-linking process.Compared with conventional quaternary ammonium-crosslinked benzimidazole membranes,the introduction of phenyl groups significantly increases the free volume within the membrane.After phosphoric acid doping,the benzimidazole membrane with larger free volume retains more phosphoric acid compared to conventional quaternary ammonium-crosslinked membranes,forming an extensive hydrogen-bonding network that effectively enhances its anhydrous proton conductivity.The anhydrous proton conductivity reaches 91 mS·cm^(-1)at 160℃,substantially higher than that of conventional quaternary ammonium-crosslinked membranes with the same mass fraction.Benefiting from the improved conductivity,the membrane electrode assembly exhibits reduced ohmic polarization,achieving a peak power density of 792 mW·cm^(-2)at 160℃.
基金supported by the National Natural Science Foundation of China(52277225)the Fundamental Research Funds for the Central Universities(xtr052024009).
文摘Proton exchange membranes(PEMs)play a central role in determining the efficiency,durability,and operational flexibility of PEM fuel cells(PEMFCs).However,conventional PEMs exhibit strong temperature-dependent proton-transport behavior,which limits their ability to support both rapid start-up at low temperatures and stable operation at elevated temperatures.Water-mediated PEMs show excellent conductivity under low-temperature and high-humidity conditions but suffer from dehydration and structural instability in the high-temperature regime.In contrast,water-independent PEMs,particularly phosphoric-acid-doped systems,conduct protons efficiently under anhydrous high-temperature conditions yet experience acid leaching that hampers room-temperature start-up and long-term durability.This review summarizes the fundamental proton-transport mechanisms that govern temperature-dependent performance and discusses recent advances in materials design aimed at enabling wide-temperature-range PEM operation.For water-mediated membranes,strategies such as incorporating hydrophilic fillers,constructing confined hydrophilic domains,and introducing additional proton-transfer sites have been developed to mitigate water loss and stabilize proton conduction.For water-independent membranes,approaches including strengthening polymer–acid interactions,engineering nanoscale confinement,designing multilayer architectures,and constructing multi–proton-carrier networks effectively improve acid retention and broaden operational temperature windows.Emerging fixed-carrier systems based on phosphonic-acid-grafted polymers,metal–organic frameworks,and covalent organic frameworks offer new pathways for stable anhydrous proton conduction across a wide temperature range.We conclude by outlining key challenges and future research opportunities,including reducing the dependence on volatile or leachable proton carriers,developing adaptive nanochannel architectures,improving anhydrous high-temperature conduction,and establishing scalable membrane fabrication methods.Continued innovation in these directions is expected to enable next-generation wide-temperature-range PEMs capable of flexible,high-efficiency operation from sub-zero to high-temperature conditions.
基金supported by the National Natural Science Foundation of China(52172170)Guangdong Natural Science Foundation for Distinguished Young Scholars(2023B1515020114)+2 种基金Fundamental Research Funds for the Central Universities(24lgqb003)Guangdong University Innovation and Enhancement Program(2024KTSCX003)Science and Technology Projects of Guangzhou(2025A04J4230).
文摘Stretchable electronics have been recognized as intriguing next-generation electronics that possess huge market value,and stretchable electronic conductors(SECs)are essential for stretchable electronics,which not only can serve as critical functional components but also are the indispensable electronic connections bridging various electronic components within stretchable electronic systems.Herein,we offer a comprehensive review of recent progress in SECs including the material categories,structure designs,fabrication techniques,and applications.The characteristics,performance enhancement strategies,and application requirements are emphasized.Based on the recent advances,the existing challenges and future prospects are outlined and discussed.
文摘Covalent organic framework ionomers enable synergistic efficient transport of protons and oxygen in medium-temperature proton exchange membrane fuel cells Proton exchange membrane fuel cells(PEMFCs),as clean and efficient energy technologies,are constrained in their performance enhancement by the sluggish oxygen reduction reaction(ORR)kinetics at the cathode,anode CO poisoning(e.g.,from methanol crossover)and intricate water management dilemmas[1].
基金supported in part by the National Key R&D Program of China under Grant 2024YFB4405300 and 2022YFA1204300the Natural Science Foundation of Hunan Province under Grant 2023JJ20016+2 种基金the National Natural Science Foundation of China under Grants of 52221001 and 62090035the Key Research and Development Plan of Hunan Province under grants of 2022GK3002 and 2023GK2012the Key Program of Science and Technology Department of Hunan Province under grant of 2020XK2001。
文摘Permeable electronics promise improved physiological comfort,but remain constrained by limited functional integration and poor mechanical robustness.Here,we report a three-dimensional(3D)permeable electronic system that overcomes these challenges by combining electrospun SEBS nanofiber mats,high-resolution liquid metal conductors patterned via thermal imprinting(50μm),and a strain isolators(SIL)that protects vertical interconnects(VIAs)from stress concentration.This architecture achieves ultrahigh air permeability(>5.09 m L cm^(-2)min^(-1)),exceptional stretchability(750%fracture strain),and reliable conductivity maintained through more than 32,500 strain cycles.Leveraging these advances,we have integrated multilayer circuits,strain sensors,and a three-axis accelerometer to achieve a fully integrated,stretchable,permeable wireless real-time gesture recognition glove.The system enables accurate sign language interpretation(98%)and seamless robotic hand control,demonstrating its potential for assistive technologies.By uniting comfort,durability,and high-density integration,this work establishes a versatile platform for nextgeneration wearable electronics and interactive human-robot interfaces.
基金supported by the IITP(Institute for Information&Communications Technology Planning&Evaluation)under the ITRC(Information Technology Research Center)support program(IITP-2025-RS-2024-00438288)grant funded by the Korea government(MSIT)+1 种基金National Research Council of Science&Technology(NST)grant by the MSIT(Aerospace Semiconductor Strategy Research Project No.GTL25051-000)supported by the IC Design Education Center(IDEC),Korea。
文摘This work presents a systematic analysis of proton-induced total ionizing dose(TID)effects in 1.2 k V silicon carbide(SiC)power devices with various edge termination structures.Three edge terminations including ring-assisted junction termination extension(RA-JTE),multiple floating zone JTE(MFZ-JTE),and field limiting rings(FLR)were fabricated and irradiated with45 Me V protons at fluences ranging from 1×10^(12) to 1×10^(14) cm^(-2).Experimental results,supported by TCAD simulations,show that the RA-JTE structure maintained stable breakdown performance with less than 1%variation due to its effective electric field redistribution by multiple P+rings.In contrast,MFZ-JTE and FLR exhibit breakdown voltage shifts of 6.1%and 15.2%,respectively,under the highest fluence.These results demonstrate the superior radiation tolerance of the RA-JTE structure under TID conditions and provide practical design guidance for radiation-hardened Si C power devices in space and other highradiation environments.
基金supported by the National Natural Science Foundation of China(Grant Nos.11804348,11775056,11975154,12225505,and 12405281)the Science Challenge(Project No.TZ2018005)+2 种基金supported by the Shanghai Pujiang Program(Grant No.23PJ1414600)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0890203)supported by the Accelerator Technology Helmholtz Infrastructure consortium ATHENA.
文摘The effects of initial spin orientation on the final electron beam polarization in laser wakefield acceleration in a pre-polarized plasma are investigated theoretically and numerically.From the results of variation of the initial spin direction,the spin dynamics of the electron beam are found to depend on the self-injection mechanism.The effects of wakefields and laser fields are studied using test particle dynamics and particle-in-cell simulations based on the Thomas-Bargmann-Michel-Telegdi equation.Compared with transverse injection,longitudinal injection is found to be preferable for obtaining a highly polarized electron beam.
基金financially supported by the Natural Science Foundation of Shandong Province (No.ZR2022QE076)the National Natural Science Foundation of China (No.52202092)the Science and Technology Support Plan for Youth Innovation of Colleges and Universities of Shandong Province of China (No.2023KJ104)。
文摘Electrochemical CO_(2) reduction reaction(CO_(2)RR) into valuable formate provides a strategy for carbon neutrality.Bismuth(Bi) catalysts,attributed to their appropriate energy barrier of OCHO*intermediate,have demonstrated substantial potential for the advancement of electrocatalytic CO_(2) reduction to formate.However,due to the weak bonding of protons(H^(*)) of Bi,the available protonate of CO_(2) on Bi is insufficient,which limits the formation of OCHO^(*).Prediction by theoretical calculation,chlorine doping can effectively promote the dissociation of H_(2)O and thus achieve effective proton supply.We prepare chlorine-doped Bi(Cl-Bi) via an electrochemical conversion strategy for electroreduction of CO_(2) .An obvious improvement of faradaic efficiency(FE) of formate(96.7% at-0.95 V vs.RHE) can be achieved on Cl-Bi,higher than that of Bi(89.4%).Meanwhile,Cl-Bi has the highest formate production rate of 275 μmol h^(-1)cm^(-2)at-0.95 V vs.RHE,which is 1.2 times higher than that of Bi(224 μmol h^(-1)cm^(-2)).In situ characterizations and kinetic analysis reveal that chlorine doping promotes the activation of H_(2)O and supply sufficient protons to promote the protonation of CO_(2) to OCHO^(*),which is consistent with theoretical calculation.The study presents an effective strategy for rational design of highly efficient electrocatalysts to promote green chemical production.
基金supported by the Advanced Materials-National Science and Technology Major Project(Grant No.2025ZD0618401)the National Natural Science Foundation of China(Grant No.12504285)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20250472)NFSG grant from BITS-Pilani,Dubai campus。
文摘The rapid advancement of machine learning based tight-binding Hamiltonian(MLTB)methods has opened new avenues for efficient and accurate electronic structure simulations,particularly in large-scale systems and long-time scenarios.This review begins with a concise overview of traditional tight-binding(TB)models,including both(semi-)empirical and first-principles approaches,establishing the foundation for understanding MLTB developments.We then present a systematic classification of existing MLTB methodologies,grouped into two major categories:direct prediction of TB Hamiltonian elements and inference of empirical parameters.A comparative analysis with other ML-based electronic structure models is also provided,highlighting the advancement of MLTB approaches.Finally,we explore the emerging MLTB application ecosystem,highlighting how the integration of MLTB models with a diverse suite of post-processing tools from linear-scaling solvers to quantum transport frameworks and molecular dynamics interfaces is essential for tackling complex scientific problems across different domains.The continued advancement of this integrated paradigm promises to accelerate materials discovery and open new frontiers in the predictive simulation of complex quantum phenomena.
基金supported by the Key R&D Program of Shandong Province(No.2023SFGC0101)Shandong Excellent Young Scientists Fund Program(Overseas)(No.2023HWYQ-047)+1 种基金the Natural Science Foundation of Shandong Province(No.ZR2022QA039)the National Natural Science Foundation of China(NSFC)(No.U2106202).
文摘Traditional digitizers for signal readout of PET detectors are based on commercial analog-to-digital converters(ADC).However,the cost and power consumption of an entire electronic readout system based on digitizers for a PET scanner are high.To address this problem,a soft-core ADC based on a field-programmable gate array(FPGA)was proposed.An FPGA-based ADC(FPGA-ADC)combines low loss and high performance.To achieve good performance,the FPGA-ADC requires three calibrations:time-to-digital converter(TDC)length calibration,TDC alignment calibration,and TDC-to-ADC calibration.A prototype front-end electronics based on FPGA-ADC was built to evaluate the performance of time-of-flight positron emission tomography(TOF PET)detectors.Each PET detector consists of a LYSO crystal single-ended coupled to a silicon photomultiplier(SiPM).The experimental results show that the full-width at half-maximum(FWHM)energy resolution for 511 keV gamma photons after saturation correction of the SiPM was 12.3%.The FWHM coincidence timing resolution(CTR)of the TOF PET detector with the readout of the front-end electronic prototype is 385.2 ps.FPGA-ADCbased front-end electronics are very promising for multichannel,low-cost,highly integrated,and power-efficient readout electronic systems for radiation detector applications.
