Enhancing the stability of Ni Fe-layered double hydroxide nanosheet array for alkaline seawater oxidation by Ce doping

Electrocatalytic hydrogen production from seawater holds enormous promise for clean energy generation.Nevertheless,the direct electrolysis of seawater encounters significant challenges due to poor anodic stability caused by detrimental chlorine chemistry.Herein,we present our recent discovery that the incorporation of Ce into Ni Fe layered double hydroxide nanosheet array on Ni foam(Ce-Ni Fe LDH/NF)emerges as a robust electrocatalyst for seawater oxidation.During the seawater oxidation process,CeO_(2)is generated,effectively repelling Cl^(-)and inhibiting the formation of Cl O-,resulting in a notable enhancement in the oxidation activity and stability of alkaline seawater.The prepared Ce-Ni Fe LDH/NF requires only overpotential of 390 m V to achieve the current density of 1 A cm^(-2),while maintaining long-term stability for 500 h,outperforming the performance of Ni Fe LDH/NF(430 m V,150 h)by a significant margin.This study highlights the effectiveness of a Ce-doping strategy in augmenting the activity and stability of materials based on Ni Fe LDH in seawater electrolysis for oxygen evolution.

Fe-doped Co3O4@C nanoparticles derived from layered double hydroxide used as efficient electrocatalyst for oxygen evolution reaction

Compared with noble metal catalyst, Co3O4-based electrocatalysts have attracted considerable interesting as low-cost alternatives for oxygen evolution reaction (OER). However, the poor electrocatalytic activity still remains a huge challenge. Herein, we demonstrate a feasible approach through oxidation of CoFe layered double hydroxide (CoFe-LDH) to synthesize Fe-doped Co3O4@C nanopmrticles with size of about 30-50 nm. As OER catalyst, the as-synthesized Fe-doped Co3O4@C nanoparticles exhibited superior OER performance with a small overpotential of 260 mV at the current density of 20 mA cm^-2, a small Tafel slope of 70 mV dec^-1 and long-term durability (there was no obviously OER current density degradation for 100 h) in alkaline solution. The present work opens a new avenue to the exploration of cost-effective and excellent electrocatalysts based on transition metal oxide materials to substitute precious metal materials for water splitting.

Electric and magnetic behaviour in double doped La2/3＋4x/3Sr1/3-4x/3Mn1-xMgxO3

The double-doped La2/3＋4x/3Sr1/3-4x/3Mn1-xMgxO3 samples with fixed Mn^3＋/Mn^4＋ ratio equal to 2/1 are investigated by means of magnetism and transport measurements. Phase separation is observed at temperature higher than T^onset c for x = 0.10 and 0.15. For x = 0.10, rather strong phase separation induces drastic magnetic random potential and results in the localization of carriers. Thus, the varlable-range hopping process dominates. For other samples, there is no or only weak phase separation above T^onset c. Thus, thermal activation mechanism is responsible for the high temperature transport behaviour. For x = 0.20 and 0.25, unexpected AFM behaviour is observed at low temperature. All these results are well understood by considering the special role of the ＂double-doping＂.

A continuous analytic channel potential solution to doped symmetric double-gate MOSFETs from the accumulation to the strong-inversion region

A continuous yet analytic channel potential solution is proposed for doped symmetric double-gate （DG） MOSFETs from the accumulation to the strong-inversion region. Analytical channel potential relationship is derived from the complete 1-D Poisson equation physically, and the channel potential solution of the DG MOSFET is obtained analytically. The extensive comparisons between the presented solution and the numerical simulation illustrate that the solution is not only accurate and continuous in the whole operation regime of DG MOSFETs, but also valid to wide doping concentration and various geometrical sizes, without employing any fitting parameter.

High-voltage super-junction lateral double-diffused metal-oxide semiconductor with a partial lightly doped pillar

A novel super-junction lateral double-diffused metal-oxide semiconductor （SJ-LDMOS） with a partial lightly doped P pillar （PD） is proposed. Firstly, the reduction in the partial P pillar charges ensures the charge balance and suppresses the substrate-assisted depletion effect. Secondly, the new electric field peak produced by the P/P junction modulates the surface electric field distribution. Both of these result in a high breakdown voltage （BV）. In addition, due to the same conduction paths, the specific on-resistance （Ron,sp） of the PD SJ-LDMOS is approximately identical to the conventional SJ-LDMOS. Simulation results indicate that the average value of the surface lateral electric field of the PD SJ-LDMOS reaches 20 V/μm at a 15 μm drift length, resulting in a BV of 300 V.

Properties and Application of Double Alkali Earth Doped Ce_ (0.9)Ca_(0.1-x) Sr_xO_( 1.90)

A series of solid solution material based on ceria, Ce 0.9 Ca 0.1- x Sr x O 1.90 ( x =0, 0 04, 0 05, 0 06), were synthesized by a solid reaction method. Ceria doped with two alkali earth elements has cubic fluorite structure. The ionic conductivity of these materials at high temperature was studied by impedance spectra, and an increasing effect of ionic conductivity was found. A maximum conductivity is achieved when the effective ionic radius is near to the critical radius (0 1106 nm). Some fuel cells were made using these materials as electrolyte. The output power and current of the SOFC with the electrolyte of double doped ceria are better than those of YSZ and single doped ceria, and the open circuit voltage of the double doped ceria is also higher than that of the single doped ones.

Electroluminescence of double-doped diamond thin films

A new electroluminescence device is fabricated by microwave plasma chemical vapour deposition system and electron beam vapour deposition system. It is comprised of highly doped silicon/diamond/boron/nitrogen-doped diamond/indium tin oxide thin films. Effects of process parameters on morphologies and structures of the thin films are detected and analysed by scanning electron microscopy, Raman spectrometer and x-ray photoelectron spectrometer. A direct-current （DC） power supply is used to drive the electroluminescence device. The blue light emission with a luminance of 1.2 cd·m^-2 is observed from this double-doped diamond thin film electroluminescence device at an applied voltage of 105 V.

Double-layer indium doped zinc oxide for silicon thin-film solar cell prepared by ultrasonic spray pyrolysis

Indium doped zinc oxide （ZnO：In） thin films were prepared by ultrasonic spray pyrolysis on corning eagle 2000 glass substrate. 1 and 2 at.% indium doped single-layer ZnO：In thin films with different amounts of acetic acid added in the initial solution were fabricated. The 1 at.% indium doped single-layers have triangle grains. The 2 at.% indium doped single-layer with 0.18 acetic acid adding has the resistivity of 6.82 × 10^-3 Ω. cm and particle grains. The doublelayers structure is designed to fabricate the ZnO：In thin film with low resistivity （2.58 × 10^-3 Ω. cm） and good surface morphology. It is found that the surface morphology of the double-layer ZnO：In film strongly depends on the substratelayer, and the second-layer plays a large part in the resistivity of the doublewlayer ZnO：In thin film. Both total and direct transmittances of the double-layer ZnO：In film are above 80% in the visible light region. Single junction a-Si：H solar cell based on the double-layer ZnO：In as front electrode is also investigated.

Interlayer distance effects on absorption coefficient and refraction index change in p-type double-δ-doped GaAs quantum wells

In the framework of the Thomas–Fermi(TF) approach, a model for the p-type double-δ-doped(DDD) system in Ga As is presented. This model, unlike other works in the literature, takes into account that the Poisson equation associated with the system is nonlinear. The electronic structure is calculated for heavy and light holes. The changes in the electronic structure result of the distance d between the doped layers are studied. In particular, the relative absorption coefficient as well as the relative refractive index change is calculated as a function of the incident photon energy for heavy holes. The effect of the interlayer distance exhibits, in the absorption coefficient, a red shift of the peak position and a decrease in amplitude when the distance increases. In addition, the relative refractive index change node has a red shift as well as the interlayer distance increases. The calculations show that the effect of the separation between layers has a greater influence on the linear terms. These results are very important for theoretical calculations and engineering of optical and electronic devices based in δ-doped Ga As.

Sb^(3+)and Sm^(3+)co-doped lead-free Cs_(2)NaInCl_(6)double perovskite nanocrystals for single-component cold white emitter

Metal halide perovskites exhibit promising prospect in light-emitting diodes,solar cells,photodetectors and bioimaging.However,the workhorse of metal halide perovskites relies on toxicity lead element,which severely damages human body and environment.Among lead-free perovskites,Cs_(2)NaInCl_(6)double perovskite is one of the most promising candidates because of its great stability and easy synthesis,but suffers inadequate optical performance.Here,we doped Sb^(3+)and Sm^(3+)into Cs_(2)NaInCl_(6)nanocrystals by a hot injection method.Cs_(2)NaInCl_(6):Sb^(3+)exhibits blue emission at 447 nm.Cs_(2)NaInCl_(6):Sm^(3+),Sb^(3+)nanocrystals simultaneously generate the blue emission of Sb^(3+)and the multiple emissions of Sm^(3+)at 565,602,650 and 710 nm.With the increase of Sm^(3+)feed ratio,the emission color of Cs_(2)NaInCl_(6):Sm^(3+),Sb^(3+)gradually moves to cold white region at(0.27,0.28)in CIE chromaticity diagram and correlated color temperature of 11840 K.This work shows the potential application of Cs_(2)NaInCl_(6):Sm^(3+),Sb^(3+)nanocrystals as a single-component cold white emitter.

Electronic structure regulation on layered double hydroxides for oxygen evolution reaction

Oxygen evolution reactions(OERs)as core components of energy conversion and storage technology systems,such as water splitting and rechargeable metal–air batteries,have attracted considerable attention in recent years.Transition metal compounds,particularly layered double hydroxides(LDHs),are considered as the most promising electrocatalysts owing to their unique two-dimensional layer structures and tunable components.However,heir poor intrinsic electrical conductivities and the limited number of active sites hinder their performances.The regulation of the electronic structure is an effective approach to improve the OER activity of LDHs,including cationic and anionic regulation,defect engineering,regulation of intercalated anions,and surface modifications.In this review,we summarize recent advances in the regulation of the electronic structures of LDHs used as electrocatalysts in OERs.In addition,we discuss the effects of each regulation type on OER activities.This review is expected to shed light on the development and design of effective OER electrocatalysts by summarizing various electronic structure regulation pathways and the effects on their catalytic performances.

Layered double hydroxide-like Mg_3Al_(1–x)Fe_x materials as supports for Ir catalysts: Promotional effects of Fe doping in selective hydrogenation of cinnamaldehyde

Supported Ir catalysts were prepared using layered double hydrotalcite‐like materials,such as Mg3Al1-xFex,containing Fe and Al species in varying amounts as supports.These Ir catalysts were applied for the selective hydrogenation of cinnamaldehyde(CAL).When x was changed from 0(Ir/Mg3Al)to 1(Ir/Mg3Fe),the rate of CAL hydrogenation reached a maximum at approximately x=0.25,while the selectivity to unsaturated alcohol,i.e.,cinnamyl alcohol,monotonously increased from 44.9%to 80.3%.Meanwhile,the size of the supported Ir particles did not change significantly with x,remaining at 1.7-0.2 nm,as determined by transmission electron microscopy.The chemical state of Ir and Fe species in the Ir/Mg3Al1-xFex catalysts was examined by temperature programmed reduction by H2 and X‐ray photoelectron spectroscopy.The surface of the supported Ir particles was also examined through the in‐situ diffuse reflectance infrared Fourier‐transform of a probe molecule of CO.On the basis of these characterization results,the effects of Fe doping to Mg3Al on the structural and catalytic properties of Ir particles in selective CAL hydrogenation were discussed.The significant factors are the electron transfer from Fe2+in the Mg3Al1–xFex support to the dispersed Ir particles and the surface geometry.

Aluminum and phosphorus codoped “superaerophobic” Co3O4 microspheres for highly efficient electrochemical water splitting and Zn-air batteries

Multifunctional non-precious catalysts for hydrogen/oxygen evolution reaction(HER/OER) and oxygen reduction reaction(ORR) constitute the bottleneck in the applications in electrochemical overall water splitting(OWS) and Zn-air batteries. Herein, a trifunctional electrocatalyst of urchin-like Al,P-codoped Co3O4 microspheres supported on Ni foam(denoted as AP-CONPs/NF) was fabricated via a hydrothermal process and subsequent low-temperature annealing and phosphorization, exhibiting enhanced OER, HER and ORR activities compared with single-doped and undoped samples. Their surface self-organized microstructure and excellent "superaerophobic" feature make a high bubble repellency, which boost diffusion of reactants and electrolyte-electrode intimate contact. The codoping of Al and P elements into Co3O4 betters right the balance among surface chemical state, the increased oxygen vacancies and the promoted charge transfer. Encouraged by these synergistic advantages, the AP-CONPs/NF was further employed as excellent bifunctional electrodes for the OWS(low cell voltage of 1.57 V at 10 mA cm-2) and as air cathode for rechargeable Zn-air batteries(high power density of 89.1 mW cm-2), which demonstrates a great feasibility for practical applications.

Tuning the oxygen evolution electrocatalysis on NiFe-layered double hydroxides via sulfur doping

We report a facile way to prepare sulfur(S) doped Ni4/5 Fe1/5-layered double hydroxide(LDH) electrocatalysts for oxygen evolution reaction(OER). The influence of S doping amount on the OER activity of the resulted Ni Fe-LDHs was studied and the optimal surface S content was ca. 0.43 at%. The developed S-doped Ni Fe-LDH exhibits excellent OER catalyst activity in 1.0 M KOH with overpotential of only 257 m V at the current density of 10 m A cm^-2. Moreover, the catalyst could maintain high activity after 30 h stability test. The high activity of the S-doped Ni Fe-LDH catalysts may originate from the synergistic effect between S and the Fe sites. This work provides a simple but efficient way to improve the OER performance of transition metal oxides/(oxy)hydroxides.

Preparation of Large-Scale Double-Side BDD Electrodes and Their Electrochemical Performances

Boron doped diamond(BDD)performs well in electrochemical oxidation for organic pollutants thanks to its wide electrochemical window and superior chemical stability.We presented a method to obtain well-adherent large-scale BDD/Nb electrode by the modified hot filament chemical vapor deposition system(HFCVD).SiC particles were sand blasted to enhance the adhesion of BDD coating.The BDD coating was then deposited on both sides of Nb which was placed vertically and closely with filament grids on both sides.The BDD/Nb electrodes had no deformation because the thermal deformations of the BDD films on both sides of the Nb substrate conteracted each other during cooling process after deposition.The surface morphology and purity of the BDD/Nb electrode were analyzed by Raman and scanning elestron microscope(SEM)techniques.Scratch test was used to investigate the adhesion of BDD films.The electrochemical performances were measured by cyclic voltammetry test.The BDD electrode at the B/C ratio of 2 000×10^(-6) held a higher oxygen evolution potential thanks to its high sp3 carbon content.Accelerated life test illustrated that the sandblasting pretreatment obviously enhanced the adhesion of BDD coating which resulted in a longer service duration than the un-sandblasted one.

Enhanced Electrochemical Capacitance of Nitrogen-Doped Carbon Nanotubes Synthesized from Amine Flames

This paper presents a new process for synthesizing a kind of nitrogen- doped carbon nanotubes (N-CNTs) with primarily a ‘graphite-like’ structure at N substitutions from flames using n-propylamine and n-butylamine as fuels. When the N-CNTs are used as the supercapacitor electrode materials, they exhibit a much larger capacitance than the regular carbon nanotubes (CNTs). It is proposed that the high proportional ‘graphite-like’ N dopant in the as-grown N-CNTs improves their surface chemical activity and conductivity and then results in a desirable performance for electro-chemical capacitors.

Achieving 20% photovoltaic efficiency by manganese doped methylammonium lead halide perovskites

We report a transition metal such as manganese doped methylammonium lead halide perovskite(MA(Pb:Mn)I_(3)) solar cell with an power conversion efficiency(PCE) over 20%. The rational design and fabrication of MA(Pb:Mn)I3 lead to the enhancements of all the photovoltaic parameters. To incorporate Mn can effectively eliminate the trap-assist and bi-molecular recombination. The photo-absorption ability at shorter wavelengths(i.e., less than 500 nm) and charge carrier lifetime can be elaborated. More importantly, the existence of the Mn^(2+)-I~--Mn^(3+)motif contributes for the double exchange effect, giving rise to the charge/spin transport. By a combination of linearly and circularly polarized photo-excitations, we have explicitly determined the role of intrinsic spin–orbit coupling(SOC) in MA(Pb:Mn)I_(3). More dark states are expected to be available for the photocurrent generation. This study may pave the way for deep understandings of transition metals doped hybrid perovskites for highly efficient solar cell applications.

钨掺杂镍铁水滑石高效电催化析氧反应

电解水对制备可持续和清洁的氢气能源至关重要。电解水的阳极析氧反应设计复杂的4-电子转移过程,所需能耗较高,是电解水的速控步骤。催化剂对于析氧反应的进行具有重要作用。镍铁水滑石是最具潜力的碱性非贵金属析氧反应(OER)催化剂,但是由于水滑石导电性差、活性位点暴露不充分、对反应中间体吸附较弱等问题,催化活性还需要进一步提高。如何提升催化活性已经被科学家们广泛关注,比如:制造缺陷、掺杂、将水滑石剥离为单层结构和组装为阵列结构等。在本论文中,通过简单的“一锅法”醇解合成了一系列不同量W掺杂NiFe-LDH的样品。XRD结果表明合成的NiFeW-LDH的衍射峰与完美NiFe-LDH标准卡片相同,没有其他的衍射峰,表明W没有单独成相,被成功掺杂进入NiFe-LDH。扫描电镜表明NiFeW-LDH为纳米片(尺寸约为~500 nm)组成的3d立体花状结构,且材料中Ni、Fe和W均匀分布。XPS表明材料中W的价态为6+,与未掺杂的NiFe-LDH相比,Fe向高价态移动,表面吸附的OH增多。在密度泛函理论(DFT)计算中,结果同样表明W6+掺杂有利于H2O和O*中间体的吸附,提高了Fe位点的活性。在1 mol∙L^(−1) KOH中,NiFeW-LDH达到10 mA·cm^(−2)所需过电位是199和237 mV,这比大多数的NiFe基粉末催化剂的性能好。综上,实验和计算表明W掺杂调控催化剂中Fe位点电子结构,优化对反应中间体的吸附,使催化剂具有更高活性。

Doping engineering of lithium-aluminum layered double hydroxides for high-efficiency lithium extraction from salt lake brines

Lithium-aluminum layered double hydroxides(LiAl-LDH)have been be successfully applied in commercial-scale for lithium extraction from salt lake brine,however,further advancement of their applications is hampered by suboptimal Li^(+)adsorption performance and ambiguous extraction process.Herein,a doping engineering strategy was developed to fabricate novel Zn^(2+)-doped LiAl-LDH(LiZnAl-LDH)with remarkable higher Li^(+)adsorption capacity(13.4 mg/g)and selectivity(separation factors of 213,834,171 for Li^(+)/K^(+),Li^(+)/Na^(+),Li^(+)/Mg^(2+),respectively),as well as lossless reusability in Luobupo brine compared to the pristine LiAl-LDH.Further,combining experiments and simulation calculations,it was revealed that the specific surface area,hydrophilic,and surface attraction for Li^(+)of LiZnAl-LDH were significantly improved,reducing the adsorption energy(Ead)and Gibbs free energy(ΔG),thus facilitating the transfer of Li^(+)from brine into interface followed by insertion into voids.Importantly,the intrinsic oxygen vacancies derived from Zn-doping depressed the diffusion energy barrier of Li^(+),which accelerated the diffusion process of Li^(+)in the internal bulk of LiZnAl-LDH.This work provides a general strategy to overcome the existing limitations of Li^(+)recovery and deepens the understanding of Li^(+)extraction on LiAl-LDH.

双包层掺铥光纤放大器中的受激布里渊散射

理论分析了波长为2μm的掺铥光纤放大器中受激布里渊散射(SBS)对激光输出性能的影响,研究了双包层掺铥光纤在793 nm的泵浦波长和1.9~2.1μm的激光工作波段的光模分布、有效折射率、有效模场面积和归一化频率,数值计算了在1.9~2.1μm的激光工作波段双包层掺铥光纤中的布里渊频移和布里渊增益谱等SBS特性。利用增益光纤中的受激布里渊散射理论模型,研究了受激布里渊散射对掺铥光纤放大器激光输出性能的影响。在DTDF-10/130双包层掺铥光纤中,使用功率为100 W、波长为793 nm的连续光作为泵浦,可对波长为2μm、功率为0.01 W的连续信号光进行放大。当泵浦光功率填充因子为0.01、0.02和0.03时,信号光的最大输出功率分别为25.27 W、31.08 W和34.06 W。对应的最佳双包层光纤长度为2.66 m、2.02 m和1.75 m,由受激布里渊散射产生的斯托克斯光功率分别为1.68 W、1.39 W和1.14 W。结果表明,在掺铥光纤放大器中使用泵浦光功率填充因子大的双包层光纤可以降低光纤长度,从而减小受激布里渊散射对信号激光输出功率的影响。本文的数值模型可以对光纤放大器的光纤长度进行优化,对提高实验效率、降低实验成本具有重要价值。