Wen Siong PohWen Jie YiangWee-Jun OngPau Loke Show...
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查看更多>>摘要：MXene has been the limelight for studies on electrode active materials,aiming at developing supercapac-itors with boosted energy density to meet the emerging influx of wearable and portable electronic devices.Despite its various desirable properties including intrinsic flexibility,high specific surface area,excellent metallic conductivity and unique abundance of surface functionalities,its full potential for elec-trochemical performance is hindered by the notorious restacking phenomenon of MXene nanosheets.Ascribed to its two-dimensional(2D)nature and surface functional groups,inevitable Van der Waals interactions drive the agglomeration of nanosheets,ultimately reducing the exposure of electrochemi-cally active sites to the electrolyte,as well as severely lengthening electrolyte ion transport pathways.As a result,energy and power density deteriorate,limiting the application versatility of MXene-based supercapacitors.Constructing 3D architectures using 2D nanosheets presents as a straightforward yet ingenious approach to mitigate the fatal flaws of MXene.However,the sheer number of distinct method-ologies reported,thus far,calls for a systematic review that unravels the rationale behind such 3D MXene structural designs.Herein,this review aims to serve this purpose while also scrutinizing the structure-property relationship to correlate such structural modifications to their ensuing electrochemical perfor-mance enhancements.Besides,the physicochemical properties of MXene play fundamental roles in determining the effective charge storage capabilities of 3D MXene-based electrodes.This largely depends on different MXene synthesis techniques and synthesis condition variations,hence,elucidated in this review as well.Lastly,the challenges and perspectives for achieving viable commercialization of MXene-based supercapacitor electrodes are highlighted.
查看更多>>摘要：In the selective oxidation of biomass-based 1,2-propanediol(PDO)with oxygen as the terminal oxidant,it is challenging to improve the lactic acid(LA)selectivity for nonnoble metal nanoparticles(NPs)due to their limited oxygen reduction rate and easy C-C cleavage.Given the high economic feasibility of nonno-ble metals,i.e.,Cu,in this work,copper and nitrogen codoped porous carbon nanosheets encapsulating ultrafine Cu nanoparticles(Cu@Cu-N-C)were developed to realize highly selective of PDO oxidation to LA.The carbon-encapsulated ultrasmall Cu0 NPs in Cu@Cu-N-C have high PDO dehydrogenation activity while N-coordinated Cu(Cu-N)sites are responsible for the high oxygen reduction efficacy.Therefore,the performance of catalytic PDO conversion to LA is optimized by a proposed pathway of PDO → hydroxylacetone → lactaldehyde → LA.Specifically,the enhanced LA selectivity is 88.5％,and the PDO conversion is up to 75.1％in an O2-pressurized reaction system(1.0 MPa O2),superior to other Cu-based catalysts,while in a milder nonpressurized system(O2 flow rate of 100 mL min-1),a remark-able LA selectivity(94.2％)is obtained with 39.8％PDO conversion,2.2 times higher than that of supported Au nanoparticles(1％Au/C).Moreover,carbon encapsulation offers Cu@Cu-N-C with strong leaching resistance for better recycling.
查看更多>>摘要：Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100％atomic utilization and exceptional catalytic functionality.Furthermore,accurately controlling atomic phys-ical properties including spin,charge,orbital,and lattice degrees of atomically dispersed catalysts can realize the optimized chemical properties including maximum atom utilization efficiency,homogenous active cen-ters,and satisfactory catalytic performance,but remains elusive.Here,through physical and chemical insight,we review and systematically summarize the strategies to optimize atomically dispersed ORR cata-lysts including adjusting the atomic coordination environment,adjacent electronic orbital and site density,and the choice of dual-atom sites.Then the emphasis is on the fundamental understanding of the correlation between the physical property and the catalytic behavior for atomically dispersed catalysts.Finally,an over-view of the existing challenges and prospects to illustrate the current obstacles and potential opportunities for the advancement of atomically dispersed catalysts in the realm of electrocatalytic reactions is offered.
查看更多>>摘要：The development of earth-abundant electrocatalysts with high performance for electrochemical CO2 reduction(ECR)is of great significance.Cu-based catalysts have been widely investigated for ECR due to their unique ability to generate various carbonaceous products,but directing selectivity toward one certain product and identifying the real active sites during ECR are still full of challenge.Here,after the incorporation of CdO into CuO,the Cu0.5Cd0.5-O catalyst achieves a 10.3-fold enhancement for CO selectivity in comparison with CuO,and a CO faradic efficiency nearly 90％with a current density around 20 mA cm-2 could maintain at least 60 h.Interestingly,a wide CO/H2 ratio(0.07-10)is reached on CuxCd1-x-O catalysts by varying the Cu/Cd ratio,demonstrating the potential of syngas production using such catalysts.The results of ex situ XRD,XPS,and in situ Raman reveal that the real active sites of Cu0.5Cd0.5-O catalysts for CO production during ECR reaction are the reconstructed mixed phases of CuCd alloy and CdCO3.In situ FTIR and theoretical calculations further implicate the presence of Cd related species promotes the CO desorption and inhibits the H2 evolution,thus leading to an enhanced CO generation.
查看更多>>摘要：Thermal runaway(TR)is a critical issue hindering the large-scale application of lithium-ion batteries(LIBs),Understanding the thermal safety behavior of LIBs at the cell and module level under different state of charges(SOCs)has significant implications for reinforcing the thermal safety design of the lithium-ion battery module.This study first investigates the thermal safety boundary(TSB)correspon-dence at the cells and modules level under the guidance of a newly proposed concept,safe electric quan-tity boundary(SEQB).A reasonable thermal runaway propagation(TRP)judgment indicator,peak heat transfer power(PHTP),is proposed to predict whether TRP occurs.Moreover,a validated 3D model is used to quantitatively clarify the TSB at different SOCs from the perspective of PHTP,TR trigger temper-ature,SOC,and the full cycle life.Besides,three different TRP transfer modes are discovered.The inter-conversion relationship of three different TRP modes is investigated from the perspective of PHTP.This paper explores the TSB of LIBs under different SOCs at both cell and module levels for the first time,which has great significance in guiding the thermal safety design of battery systems.
查看更多>>摘要：The electrolyte directly contacts the essential parts of a lithium-ion battery,and as a result,the electro-chemical properties of the electrolyte have a significant impact on the voltage platform,charge discharge capacity,energy density,service life,and rate discharge performance.By raising the voltage at the charge/discharge plateau,the energy density of the battery is increased.However,this causes transition metal dissolution,irreversible phase changes of the cathode active material,and parasitic electrolyte oxidation reactions.This article presents an overview of these concerns to provide a clear explanation of the issues involved in the development of electrolytes for high-voltage lithium-ion batteries.Additionally,solid-state electrolytes enable various applications and will likely have an impact on the development of bat-teries with high energy densities.It is necessary to improve the high-voltage performance of electrolytes by creating solvents with high thermal stabilities and high voltage resistance and additives with superior film forming performance,multifunctional capabilities,and stable lithium salts.To offer suggestions for the future development of high-energy lithium-ion batteries,we conclude by offering our own opinions and insights on the current development of lithium-ion batteries.
查看更多>>摘要：Industry decarbonization requires the development of highly efficient and flexible technologies relying on renewable energy resources,especially biomass and solar/wind electricity.In the case of pure oxygen production,oxygen transport membranes(OTMs)appear as an alternative technology for the cryogenic distillation of air,the industrially-established process of producing oxygen.Moreover,OTMs could pro-vide oxygen from different sources(air,water,CO2,etc.),and they are more flexible in adapting to current processes,producing oxygen at 700-1000 ℃.Furthermore,OTMs can be integrated into catalytic mem-brane reactors,providing new pathways for different processes.The first part of this study was focused on electrification on a traditional OTM material(Ba0.5Sr0.5Co0.8Fe0.2O3-δ),imposing different electric cur-rents/voltages along a capillary membrane.Thanks to the emerging Joule effect,the membrane-surface.temperature and the associated O2 permeation flux could be adjusted.Here,the OTM is electrically and locally heated and reaches 900 ℃ on the surface,whereas the surrounding of the membrane was maintained at 650 ℃.The O2 permeation flux reached for the electrified membranes was～3.7 NmL min-1 cm-2,corresponding to the flux obtained with an OTM non-electrified at 900 ℃.The influence of depositing a porous Ce0.8Tb0.2O2-δ catalytic/protective layer on the outer membrane surface revealed that lower surface temperatures(830 ℃)were detected at the same imposed electric power.Finally,the electrification concept was demonstrated in a catalytic membrane reactor(CMR)where the oxidative dehydrogenation of ethane(ODHE)was carried out.ODHE reaction is very sensitive to temper-ature,and here,we demonstrate an improvement of the ethylene yield by reaching moderate tempera-tures in the reaction chamber while the O2 injection into the reaction can be easily fine-tuned.
查看更多>>摘要：While alloying transition metal chalcogenides(TMCs)with other chalcogen elements can effectively improve their conductivity and electrochemical properties,the optimal alloying content is still uncertain.In this study,we study the influence of dopant concentration on the chemical bonds in TMC and reveal the associated stepwise conversion reaction mechanism for potassium ion storage.According to density function theory calculations,appropriate S-doping in Co0.85Se(Co0.85Se1-xSx)can reduce the average length of Co-Co bonds because of the electronegativity variation,which is thermodynamically favour-able to the phase transition reactions.The optimal Se/S ratio(x=0.12)for the conductivity has been obtained from experimental results.When assembled as an anode in potassium-ion batteries(PIBs),the sample with optimized Se/S ratio exhibits extraordinary electrochemical performance.The rate per-formance(229.2 mA h g-1 at 10 A g-1)is superior to the state-of-the-art results.When assembled with Prussian blue(PB)as a cathode,the pouch cell exhibits excellent performance,demonstrating its great potential for applications.Moreover,the stepwise K+storage mechanism caused by the coexistence of S and Se is revealed by in-situ X-ray diffraction and ex-situ transmission electron microscopy techniques.Hence,this work not only provides an effective strategy to enhance the electrochemical performance of transition metal chalcogenides but also reveals the underlying mechanism for the construction of advanced electrode materials.
查看更多>>摘要：Owing to the utilization of lithium metal as anode with the ultrahigh theoretical capacity density of 3860 mA h g-1 and oxide-based ceramic solid-state electrolytes(SE),e.g.,garnet-type Li7La3Zr2O12(LLZO),all-state-state lithium metal batteries(ASLMBs)have been widely accepted as the promising alternatives for providing the satisfactory energy density and safety.However,its applications are still challenged by plenty of technical and scientific issues.In this contribution,the co-sintering temperature at 500 ℃ is proved as a compromise method to fabricate the composite cathode with structural integrity and declined capacity fading of LiNi0.5Co0.2Mn0.3O2(NCM).On the other hand,it tends to form weaker grain boundary(GB)inside polycrystalline LLZO at inadequate sintering temperature for LLZO,which can induce the intergranular failure of SE during the growth of Li filament inside the unavoidable defect on the interface of SE.Therefore,increasing the strength of GB,refining the grain to 0.4 μm,and preclud-ing the interfacial defect are suggested to postpone the electro-chemo-mechanical failure of SE with weak GB.Moreover,the advanced sintering techniques to lower the co-sintering temperature for both NCM-LLZO composite cathode and LLZO SE can be posted out to realize the viability of state-of-the-art ASLMBs with higher energy density as well as the guaranteed safety.
查看更多>>摘要：The parasitic hydrogen evolution reaction(HER)in the negative half-cell of vanadium redox flow batter-ies(VRFBs)causes severe efficiency losses.Thus,a deeper understanding of this process and the accom-panying bubble formation is crucial.This benchmarking study locally analyzes the bubble distribution in thick,porous electrodes for the first time using deep learning-based image segmentation of synchrotron X-ray micro-tomograms.Each large three-dimensional data set was processed precisely in less than one minute while minimizing human errors and pointing out areas of increased HER activity in VRFBs.The study systematically varies the electrode potential and material,concluding that more negative electrode potentials of-200 mV vs.reversible hydrogen electrode(RHE)and lower cause more substantial bubble formation,resulting in bubble fractions of around 15％-20％in carbon felt electrodes.Contrarily,the bub-ble fractions stay only around 2％in an electrode combining carbon felt and carbon paper.The detected areas with high HER activity,such as the border subregion with more than 30％bubble fraction in carbon felt electrodes,the cutting edges,and preferential spots in the electrode bulk,are potential-independent and suggest that larger electrodes with a higher bulk-to-border ratio might reduce HER-related perfor-mance losses.The described combination of electrochemical measurements,local X-ray micro-tomography,AI-based segmentation,and 3D morphometric analysis is a powerful and novel approach for local bubble analysis in three-dimensional porous electrodes,providing an essential toolkit for a broad community working on bubble-generating electrochemical systems.
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