First-principle calculation of distorted T-carbon as a promising anode for Li-ion batteries with enhanced capacity, reversibility, and ion migration properties

Carbon group element-based materials are the most widely used anode materials for Li-ion batteries(LIBs).However,their performance is limited by the low capacity(eg,graphite)or high-volume changes(eg,Si and Sn).Therefore,exploring high-performance anode materials is quite appealing and promising.By first-principle calculations in this study,we found that distorted T-carbon(DTC)as a desired LIB anode shows properties of the enhanced capacity,decreased volume change,and the increased ion migration.The origin of such improved properties is attributed to the interconnected tunnels and large cavities of the carbon skeleton.The theoretical specific capacity of DTC is found to be 558 mAh/g,which is 1.5 times higher than that of commercial graphite anodes.Interestingly,the volume change of the DTC anode is only 3%at the full-lithiation state(one-fifth of that of the commercial graphite anode),which can overcome the pulverization problem in most high-capacity anode materials and attain a longer cycling lifetime.Both transition state calculations and molecular dynamics simulations demonstrate that the Li-ion migration barrier is less than 0.1 eV and the Li-ion vacancy is only 0.2 eV,enabling its promising rate performance.This study provides a new and effective strategy to improve the anode properties of LIBs.

Millimeter-Wave Heterodyne Six-Port Receiver:New Implementation and Demodulation Results

This paper presents a new implementation of a millimeter-wave heterodyne receiver based on six-port technology. The six-port model is implemented in Advanced Design System （ADS） using S-parameter measurements for realistic advanced simulation of a short-range 60 GHz wireless link. Millimeter-wave frequency conversion is performed using a six-port down-converter. The second frequency conversion is performed using conventional means because of low IF. A comparison between the proposed receiver and a conventional balanced millimeter-wave mixer shows that the proposed receiver improves conversion loss and I/Q phase stability over the local oscillator （LO） and RF power ranges. The results of demodulating a V-band quadrature phase-shift keying （QPSK） signal at a high data rate of 100 Mb/s-1 Gb/s are discussed. The results of a bit error rate （BER） and error vector magnitude （EVM） analysis prove that the proposed architecture can be successfully used for wireless link transmission up to 10 m.

Thermodynamics and kinetics of hydriding and dehydriding reactions in Mg-based hydrogen storage materials

Mg-based materials are one of the most promising hydrogen storage candidates due to their high hydrogen storage capacity,environmental benignity,and high Clarke number characteristics.However,the limited thermodynamics and kinetic properties pose major challenges for their engineering applications.Herein,we review the recent progress in improving their thermodynamics and kinetics,with an emphasis on the models and the influence of various parameters in the calculated models.Subsequently,the impact of alloying,composite,and nanocrystallization on both thermodynamics and dynamics are discussed in detail.In particular,the correlation between various modification strategies and the hydrogen capacity,dehydrogenation enthalpy and temperature,hydriding/dehydriding rates are summarized.In addition,the mechanism of hydrogen storage processes of Mg-based materials is discussed from the aspect of classical kinetic theories and microscope hydrogen transferring behavior.This review concludes with an outlook on the remaining challenge issues and prospects.

Single-Atom Catalysts for Electrochemical Hydrogen Evolution Reaction: Recent Advances and Future Perspectives

Hydrogen,a renewable and outstanding energy carrier with zero carbon dioxide emission,is regarded as the best alternative to fossil fuels.The most preferred route to large-scale production of hydrogen is by water electrolysis from the intermittent sources(e.g.,wind,solar,hydro,and tidal energy).However,the efficiency of water electrolysis is very much dependent on the activity of electrocatalysts.Thus,designing high-effective,stable,and cheap materials for hydrogen evolution reaction(HER)could have a substantial impact on renewable energy technologies.Recently,single-atom catalysts(SACs)have emerged as a new frontier in catalysis science,because SACs have maximum atom-utilization efficiency and excellent catalytic reaction activity.Various synthesis methods and analytical techniques have been adopted to prepare and characterize these SACs.In this review,we discuss recent progress on SACs synthesis,characterization methods,and their catalytic applications.Particularly,we highlight their unique electrochemical characteristics toward HER.Finally,the current key challenges in SACs for HER are pointed out and some potential directions are proposed as well.

Atomically Dispersed Fe-Co Bimetallic Catalysts for the Promoted Electroreduction of Carbon Dioxide

The electroreduction reaction of CO_(2)(ECO_(2)RR)requires high-performance catalysts to convert CO_(2)into useful chemicals.Transition metal-based atomically dispersed catalysts are promising for the high selectivity and activity in ECO_(2)RR.This work presents a series of atomically dispersed Co,Fe bimetallic catalysts by carbonizing the Fe-introduced Co-zeolitic-imidazolate-framework(C-Fe-Co-ZIF)for the syngas generation from ECO_(2)RR.The synergistic effect of the bimetallic catalyst promotes CO production.Compared to the pure C-Co-ZiF,C-Fe-Co-ZIF facilitates CO production with a CO Faradaic efficiency(FE)boost of 10%,with optimal FE_(CO)of 51.9%,FE_(H_(2))of 42.4%at-0.55 V,and CO current density of 8.0 mA cm^(-2)at-0.7 V versus reversible hydrogen electrode(RHE).The H_(2)/CO ratio is tunable from 0.8 to 4.2 in a wide potential window of-0.35 to-0.8 V versus RHE.The total FE_(CO+H_(2))maintains as high as 93%over 10 h.The proper adding amount of Fe could increase the number of active sites and create mild distortions for the nanoscopic environments of Co and Fe,which is essential for the enhancement of the CO production in ECO_(2)RR.The positive impacts of Cu-Co and Ni-Co bimetallic catalysts demonstrate the versatility and potential application of the bimetallic strategy for ECO_(2)RR.

锆和钽基氧气还原反应催化剂的简易合成(英文)

Cathode catalysts for direct alcohol fuel cells(DAFCs) must have high catalytic activity for the oxy-gen reduction reaction(ORR), low cost, and high tolerance to the presence of methanol or ethanol. Pt is the benchmark catalyst for this application owing to its excellent electrocatalytic activity, but its high cost and low tolerance to the organic fuel permeating through the membrane have hindered the commercialization of DAFCs. Herein we present a facile synthesis route to obtain organic fuel-tolerant Zr- and Ta-based catalysts supported on carbon. This method consists of a simple precipitation of metal precursors followed by a heat treatment. X-ray diffraction analyses confirmed that the obtained samples were crystalline ZrO 2-x and Na2Ta8O21-x having crystallite sizes of 26 and 32 nm, respectively. The thermal treatment effectively increased the activity of the catalysts to-wards the ORR, although further optimization is necessary. Both catalysts exhibited a high tolerance to the presence of methanol with only a moderate reduction in ORR activity even at high methanol concentration(0.5 mol/L).

Advances in Digital Front-End and Software RF Processing: PartⅡ

In the first editorial of this two-part special issue, we pointed out that one of the biggest trends in wireless broadband, radar, sonar, and broadcasting technology is software RF processing and digital front-end [1]. Thistrend encompasses signal processing algorithms and integrated circuit design and includes digital pre-distortion （DPD）, conversions between digital and analog signals, digita up-conversion （DUC）, digital down-conversion （DDC）, DC offset,

The degradation of cathodic Fe/N/C catalyst in PEMFCs:The evolution of remanent active sites after demetallation

The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant activity decay in real-world PEMFC cells.The superposed“fast decay”and“slow decay”have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation.The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test.Nevertheless,it is still unclear how the remanent active sites evolve after demetallation.To this end,the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies(MEAs)after different operations.It is presented that 1 bar pressure and 80℃ temperature are the optimized conditions for Fe/N/C MEA.Particularly,the“fast decay”in the initial 15 h is immune to the various operating parameters,while the“slow decay”highly depends on the applied temperature and pressure.According to the X-ray absorption spectra(XAS)analysis and stability test of MEA,the gradual evolution of Fe-N coordination to Fe-O is found correlated with the“slow decay”and accounts for the catalyst decay after the demetallation process.

Rare earth element-modified MOF materials:synthesis and photocatalytic applications in environmental remediation

Metal-organic framework-like materials(MOFs)have been developed in the fields of photocatalysis for their excellent optical properties and physicochemical properties,including environmental remediation,CO_(2)photoreduction,water splitting,and so on.With their important roles in various fields,rare earth elements have received growing interests from scientists.Modifying MOFs with rare earth elements for modification allows broadening the absorption spectrum,while the active electrons on their empty 4f orbitals can act as traps to capture photoexcited carriers to inhibit the recombination of electron-hole pairs,thus promoting photocatalytic activity.Therefore,rare earth elements modified MOFs provide an attractive way to achieve their high value utilization.In this mini-review,the synthesis of rare earth element-modified MOFs photocatalysts and corresponding applications in the removal of antibiotics,CO_(2)reduction,and hydrogen production are constructively summarized and discussed.Finally,the latest advancements and current difficulties of these materials as well as the application prospects are also provided.

Ultra-thin ALD CoO_(x)-ZnO heterogenous films as highly sensitive and environmentally friendly H_(2)S sensor

To obtain environmentally friendly,integrated and miniaturized gas sensors for the increasing request for the Internet of Things industry and other relative areas,the ultra-thin CoO_(x)/Zn O heterogeneous film with active interfacial sites was in-situ deposited on micro-electro-mechanical systems(MEMS)as H_(2)S sensor.Atomic layer deposition(ALD)was employed to in-situ fabricate the uniform Zn O thin film.ALD CoO_(x)was deposited on ZnO surface to obtain CoO_(x)/Zn O heterojunction and active interfacial sites.The ultra-thin film(20 nm)with 50 ALD Co O_(x)decorated on 250 ALD Zn O displays excellent sensing performance,including very high response(4.45@200×10^(-9))and selectivity to H_(2)S with a limit of detection(LOD)of 0.38×10^(-9),long-term sensing stability,high response/recovery performance(7.5 s/15.7 s)and mechanical strength at 230。C.Reasons for the high sensing performance of CoO_(x)/Zn O have been confirmed by series of characterizations and density functional theory(DFT)calculation.Heterojunction film thickness with Debye length,the oxygen vacancies and the synergistic effect of active interfacial sites are main reasons for the high sensing performance.The strategy by fabrication of CoO_(x)/Zn O heterogeneous film within Debye length and employing synergistic effect of active interfacial sites offers a promising route for the design of environmentally friendly gas sensors.Furthermore,the ALD technique offers a facile in-situ strategy and high-throughput fabrication of MEMS gas sensors.