Doping effect of cations(Zr^(4+),Al^(3+),and Si^(4+)) on MnO_x/CeO_2 nano-rod catalyst for NH_3-SCR reaction at low temperature

Thermally stable Zr4+, Al3+, and Si4+ cations were incorporated into the lattice of CeO2 nano‐rods (i.e., CeO2‐NR) in order to improve the specific surface area. The undoped and Zr4+, Al3+, and Si4+ doped nano‐rods were used as supports to prepare MnOx/CeO2‐NR, MnOx/CZ‐NR, MnOx/CA‐NR, and MnOx/CS‐NR catalysts, respectively. The prepared supports and catalysts were comprehensively characterized by transmission electron microscopy (TEM), high‐resolution TEM, X‐ray diffraction, Raman and N2‐physisorption analyses, hydrogen temperature‐programmed reduction, ammonia temperature‐programmed desorption, in situ diffuse reflectance infrared Fourier‐transform spectroscopic analysis of the NH3 adsorption, and X‐ray photoelectron spectroscopy. Moreover, the catalytic performance and H2O+SO2 tolerance of these samples were evaluated through NH3‐selective catalytic reduction (NH3‐SCR) in the absence or presence of H2O and SO2. The obtained results show that the MnOx/CS‐NR catalyst exhibits the highest NOx conversion and the lowest N2O concentration, which result from the largest number of oxygen vacancies and acid sites, the highest Mn4+ content, and the lowest redox ability. The MnOx/CS‐NR catalyst also presents excellent resistance to H2O and SO2. All of these phenomena suggest that Si4+ is the optimal dopant for the MnOx/CeO2‐NR catalyst.

Doping effects of manganese on the catalytic performance and structure of NiMgO catalysts for controllabe synthesis of multi-walled carbon nanotubes

Doping effects of manganese （Mn） on catalytic performance and structure evolution of NiMgO catalysts for synthesis of multi-walled carbon nanotubes （MWCNTs） from methane were investigated for the first time. Addition of Mn in NiMgO catalyst can greatly improve the MWCNTs yield. Mno.2NiMgO catalyst among the tested ones gives the highest MWCNTs yield as 2244%, which is two times higher than that of the catalyst without Mn. The structure evolution, reduction behaviors and surface chemical properties of MnNiMgO catalysts with various Mn contents were studied in detail. It was found that the stable solid solution of NiMgO2 formed in NiMgO catalyst was disturbed by the addition of Mn. Instead, another solid solution of MnMg608 is formed. More amount of Ni can be reduced and dispersed on the catalyst surface to be acted as active sites. Importantly, the changes of Ni content on the surface are correlated with the Ni particle size and the outer diameter of MWCNTs, suggesting the controllable synthesis of MWCNTs over MnNiMgO catalysts.

Rare Earth Doping Effects on Properties of Ceria-Zirconia Solid Solution

Ce0.6Zr0.3RE0.1O2(RE = Y, La, Pr, Tb)solid solutions were prepared by co-precipitation technique and characterized by a series of methods. XRD and FT-Raman results show that Ce0.6Zr0.3RE0.1O2 has cubic fluorite structure. The different dopant ion radii bring different effect on the cell parameter of Ce0.6Zr0.3RE0 1O2. The X-ray photoelectron spec-troscopy (XPS) results show that the binding energy of Ce3d, Zr3d and O1s for Ce0.6Zr0.3RE0.1O2 rises compared with that for Ce0.6Zr0.4O2, indicating that dopant elements change chemistry environment of solid solutions which is available to improve redox performance. Compared with Pd/Ce0.6Zr0.4O2, doping Y and La does not change air/fuel (A/F) characteristic of TWCs, but doping Pr and Tb widens A/F operating window and makes HC, CO and NO have higher conversion. The light-off temperature of Pd/Ce0.6Zr0.3La0.1O2 is corresponding to that of Pd/Ce0.6Zr0.4O2. However, the light-off temperatures of Pd/Ce0.6Zr0.3M0.1O2(M = Y, Pr, Tb) are lower than that of Pd/Ce0.6Zr0.4O2, which keep much lower after high temperature treatments. Among Pd/Ce0.6Zr0.3RE0.1 O2, Pd/Ce0.6Zr0.3Tb0.1 O2 represents wider A/F operating window, higher conversion, lower light-off temperature and better high-temperature resistance.

Doping Effect of CuO on CeO_2 for CO Oxidation

Cu-Ce-O catalysts, prepared by the amorphous citrate precursor (ACP) method, wereinvestigated by ICP, XRD and ndcro-reactor techniques. At low copper content of Cu-Ce-Ocatalysts, fluorite structures formed at low calcining temperatures, and Cuo doped into the CeO2matrix; at high copper content, in addition to the fluorite structure, crystalline monoclinic phaseCuO formed as well at high calcining temperatures. There was no other phase formed even calcinedat 1000℃. The results show that only a little CuO dopes into the CeO2 matrix to form complexoxide, which promotes the catalytic activity of CO oxidation greatly. The optimum Cu-Ce-Ocatalyst is composed of 15% copper by Cu/(Ce+Cu) atomic ratio, and calcined at 700℃ for 4h. Thephase compositions include the crystalline CuO and the active complex oxide with fluoritestructure. The formulation of the active complex oxide is Cu0.06Ce0. 94O1.94.

A Comparative Study of Boron and Phosphorus Doping Effects in SiC: H Films Prepared by ECR-CVD

Hydrogenated silicon carbide films (SiC:H) were deposited using the electron cyclotron resonance chemical vapour deposition (ECR-CVD) technique from a mixture of methane, silane and hydrogen, and using diborane and phosphine as doping gases. The effects of changes in the microwave power on the deposition rate and optical bandgap were investigated, and variations in the photoand dark-conductivities and activation energy were studied in conjunction with film analysis using the Raman scattering technique. In the case of boron-doped samples, the conductivity increased rapidly to a maximum, followed by rapid reduction at high microwave power. The ratio of the photo- to dark-conductivity (σph/σd) peaked at microwave power of ~600 W. Under conditions of high microwave power, Raman scattering analysis showed evidence of the formation and increase in the silicon microcrystalline and diamond-like phases in the films, the former of which could account for the rapid increase and the latter the subsequent decrease in the conductivity.In the case of phosphorusdoped SiC:H samples, it was found that increase in the microwave power has the effect of enhancing the formation of the silicon microcrystalline phase in the films which occurred in correspondence to a rapid increase in the conductivity and reduction in the activation energy The conductivity increase stabilised in samples deposited at microwave power exceeding 500 W probably as a result of dopant saturation. Results from Raman scattering measurements also showed that phosphorus doping had the effect of enhancing the formation of the silicon microcrystals in the film whereas the presence of boron had the effect of preserving the amorphous structure.

Doping effect on the structure and physical properties of quasi-one-dimensional compounds Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15)(x=0-0.2)

A series of samples of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15)(x=0,0.05,0.1,0.15,0.2)with quasi-one-dimensional(1D)structure were successfully synthesized under high-temperature and high-pressure conditions.The influence of partial substitution of S for Se on the structure,electronic transport,and magnetic properties of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15) has been investigated in detail.The x-ray diffraction data shows that the lattice constant decreases linearly with increasing S-doping level,which follows the Vegrad’s law.The doped S atoms preferentially occupy the site of Se atoms in CoSe6 octahedron.Physical properties measurements indicate that all the samples of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15) are semiconducting and display spin glass behavior.As the replacement of Se by smaller size S,although the inter-chain distance decreases,the electronic hopping between CoSe/S6 chains is weakened and leads to an increase of band gap from 0.75 eV to 0.86 eV,since the S-3p electrons are more localized than Se-4p ones.Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15) exhibits 1D conducting chain characteristic.

Doping Effect of Co at Ag Sites in Antiperovskite Mn3AgN Compounds

Antiperovskite compounds Mn3Ag1-xCoxN （x =0.2, 0.5 and 0.8） are synthesized and the doping effect of the magnetic element Co at the Ag site is investigated. The crystal structure is not changed by the introduction of Co. However, with the increase of the content of Co, the spin reorientation gradually disappears and the antiferromagnetic transition changes to the ferromagnetic transition at the elevated temperature when x = 0.8. In addition, all of the magnetic phase transitions at the elevated temperature are always accompanied by the abnormal thermal expansion behaviors and an entropy change. Moreover, when x = 0.8, the coefficient of linear expansion is -1.89 × 10^-6 K^-1 （290-310K, △T =20 K）, which is generally considered as the low thermal expansion.

Doping effects on the electro-degradation of phenol on doped titanium suboxide anodes

Titanium suboxide is an excellent electrode material for many oxidization reactions.In this article,the electrodes of pure Ti_4O_7,doped Ti_4O_7and the mixed-crystal of Ti_4O_7and Ti_5O_9were prepared to evaluate their activities and doping effects in the electro-degradation of phenol.It was revealed by the HPLC analysis results that the degradation intermediates and routes were significantly affected by the doping element.On the pure Ti_4O_7anode,a series of classic intermediates were obtained from benzoquinone and hydroquinone to various carboxylic acids.These intermediates were degraded gradually to the final organic intermediate of oxalate in all experiments.At last,oxalate was oxidized to CO_2and H_2O.Distinctively,the Y-doped Ti_4O_7 anode directly broke phenol toα-ketoglutaric acid without the intermediates of benzoquinone and hydroquinone.The strong oxidization ability of the Y-doped Ti_4O_7 anode might be responsible for the highest COD removal ratio.In contrast,the Ga-doped Ti_4O_7 anode showed the worst degradation activity in this article.Three intermediates of benzoquinone,hydroquinone and maleic acid were found during the degradation.Benefiting from the weak ability,oxalate was efficiently accumulated with a very high yield of 74.6%.The results demonstrated promising applications from electrochemical preparation to wastewater degradation by adjusting the doping reagent of Ti_4O_7 electrodes.

Surface doping effect on the optoelectronic performance of 2D organic crystals based on cyano-substituted perylene diimides

Compared to organic thin films,organic single crystals offer significant potential in organic phototransistors(OPTs)due to their enhanced charge transport,large surface area,and defect-free nature.However,the development of n-type semiconductors has lagged behind p-type semiconductors.To enhance semiconductor device performance,a doping process can be employed,which typically involves the introduction of charged impurities into the crystalline semiconducting material.Its aim is to reduce the Ohmic losses,increase carrier density,improve transport capabilities,and facilitate effective carrier injection,ultimately enhancing the electrical properties of the material.Traditional doping processes,however,often pose a risk of damaging the structure of single crystals.In this study,we have synthesized novel cyanosubstituted chiral perylene diimides,which self-assemble into two-dimensional single crystals that can be used for n-type semiconductor devices.We have employed a surface doping strategy using diethylamine vapor without disrupting the crystal structure.The fabricated devices exhibit significantly higher charge transport properties after doping,achieving a maximum electron mobility of 0.14 cm^(2)V^(-1)s^(-1),representing an improvement of over threefold.Furthermore,the optoelectronic performance of the doped devices has significantly improved,with the external quantum efficiency increased by over 9 times and the significantly improved response time.These results suggest that our surface doping technology is a promising way for enhancing the performance of 2D organic single-crystal OPTs.

Doping effect of rare earth metal ions Sm^(3+),Nd^(3+)and Ce^(4+)on denitration performance of MnO_(x) catalyst in low temperature NH_(3)-SCR reaction

The MnXO_(x) catalysts(i.e.,MnSmO_(x),MnNdO_(x),MnCeO_(x)) were prepared by reverse co-precipitation method and used for NH_(3)-SCR reaction.It is found that MnCeO_(x) catalyst presents the best low tempe rature catalytic activity(higher than 90% NO_(x) conversion in the te mperature range from 125 to 225℃)and excellent H_(2)O+SO_(2) resistance.In order to explore the reason for this result,the characterization of X-ray diffraction(XRD),Raman spectroscopy,Brunauer-Emmett-Teller(BET),H_(2)-temperature programmed reduction(H_(2)-TPR),NH_(3)-temperature programmed desorption(NH_(3)-TPD),X-ray photoelectron spectroscopy(XPS) and in situ diffuse reflaxions infrared Fourier transformations spectroscopy(DRIFTS) were conducted.The obtained results suggest that MnCeO_(x) catalyst shows the largest amount of acid sites and the best reducibility among these MnXO_(x) catalysts.Besides,Ce^(4+) doping inhibits the crystallization of MnO_(x) catalyst and shows the largest specific surface area.Finally,in situ DRIFTS experiments reveal that NH_(3)-SCR reaction over MnCeO_(x) catalyst follows both Langmuir-Hinshelwood(LH) and Eley-Rideal(E-R) mechanisms,which is through "fast SCR" reaction.

Selective core-shell doping enabling high performance 4.6 V-LiCoO_(2)

Constructing robust surface and bulk structure is the prerequisite for realizing high performance high voltage LiCoO_(2)(LCO).Herein,we manage to synthesize a surface Mg-doping and bulk Al-doping coreshell structured LCO,which demonstrates excellent cycling performance.Half-cell shows 94.2%capacity retention after 100 cycles at 3.0-4.6 V(vs.Li/Li^(+))cycling,and no capacity decay after 300 cycles for fullcell test(3.0-4.55 V).Based on comprehensive microanalysis and theoretical calculations,the degradation mechanisms and doping effects are systematically revealed.For the undoped LCO,high voltage cycling induces severe interfacial and bulk degradations,where cracks,stripe defects,fatigue H2 phase,and spinel phase are identified in grain bulk.For the doped LCO,Mg-doped surface shell can suppress the interfacial degradations,which not only stabilizes the surface structure by forming a thin rock-salt layer but also significantly improves the electronic conductivity,thus enabling superior rate performance.Bulk Al-doping can suppress the lattice"breathing"effect and the detrimental H3 to H1-3 phase transition,which minimizes the internal strain and defects growth,maintaining the layered structure after prolonged cycling.Combining theoretical calculations,this work deepens our understanding of the doping effects of Mg and Al,which is valuable in guiding the future material design of high voltage LCO.

Doping of group IVB elements for nickel-rich cobalt-free cathodes

Hetero-element doping is a promising strategy to improve the cycling stability of nickel-rich cobalt-free cathodes for the next-generation high energy-density Li ion batteries.To make doping effective,it is important to understand the mechanism of how the dopants regulate the electronic band,lattice parameter adjusting,or hetero-phase formation to achieve high stability.In this study,we investigate LiNi_(0.9)Mn_(0.1)O_(2)cathodes doped with IVB grouping elements via multiple characterization techniques.By utilizing in situ XRD and TEM methods,we found that the stronger Ti-O bond effectively improves the cathode stability via a dual protection mechanism.Specifically,the bulk lattice of cathode is wellpreserved during cycling as a result of the suppressed H_(2)-H_(3)phase transition,while a in situ formed Ti-rich surface layer can prevent continuous surface degradation.As a result,the 5%Ti doped LiNi_(0.9)Mn_(0.1)O_(2)cathode exhibits a high capacity retention of 96%after 100 cycles.Whereas,despite IVB group elements Zr and Hf have stronger bonding energy with oxygen,their larger ionic radii actually impede their diffusion into the cathode,thereby they can not improve the cycling stability.Our findings uncover the functional origin of doped elements with their dynamic modification on cathode structure,providing mechanistic insights into the design of nickel-rich cobalt-free cathodes.

Effects of Doping on the Magnetic Properties and Frustration of Hexagonal YMn0.9A0.1O3（A=Al,Fe,and Cu）

The doping effects on the frustration and the magnetic properties in hexagonal compounds ot YMn0.9A0.1O3 （A=A1, Fe and Cu） are investigated. Experimental results indicate that both the non-magnetic and magnetic ion dopants lead to the increase of magnetic moments and the decrease of the absolute value of Curie-Weiss temperature （｜θcw｜）- Compared with pure YMnOa, the geometrical frustration of YMn0.9 A0. 1O3 is greatly suppressed and the magnetic coupling in that exhibits dopant-dependent. In addition, for the doped YMno.gAo.103, the antiferromagnetic transition temperature （TN） is also suppressed slightly, which shows an abnormal dilution effect and it may be ascribed to the reduction of frustration due to the chemical substitution.

Effect of Chemical Doping on the Electronic Transport Properties of Tailoring Graphene Nanoribbons

The electronic transport properties of a molecular junction based on doping tailoring armchair-type graphene nanoribbons（AGNRs）with different widths are investigated by applying the non-equilibrium Green＇s function formalism combined with first-principles density functional theory.The calculated results show that the width and doping play significant roles in the electronic transport properties of the molecular junction.A higher current can be obtained for the molecular junctions with the tailoring AGNRs with W=11.Furthermore,the current of boron-doped tailoring AGNRs with widths W=7 is nearly four times larger than that of the undoped one,which can be potentially useful for the design of high performance electronic devices.

Characteristics of In_(0.52)Al_(0.48)As Grown on InP(100) Substrates by Molecular Beam Epitaxy: Growth Optimisation and Effects of Si Doping

Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at a wide range of substrate tempreatures (470~550℃) and at different Si doping levels has been carried out. Low temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) analyses shaw a strong dependence of the PL and XRD linewidths, XRD intensity ratio (Lepi/Isub), and lattice-mismatch on the substrate temperature. The X-ray diffraction peaks of samples grown at law temperatures show a composition of smaller peaks, indicating the presence of disorder due to alloy clustering. Raman scattering measurements of the same samples show an additional higher energy mode at 273 cm-1 in addition to the InAs-like and AlAs-like longitudinal-optic (LO) phonon modes. Samples doped with Si show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. Supported be observations of a reduction in both the AlAs-like and InAs-like LO phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased, the PL intensity also shows in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.

Effect of Crystallinity of Fullerene Derivatives on Doping Density in the Organic Bulk Heterojunction Layer in Polymer Solar Cells

Polymer solar cells （PSCs） based on poly（3-hexylthiophene） （P3HT） and [6,6]-phenyl-C61-butyric acid methyl ester （PCBM） are fabricated by using 1,8-diiodooctane （DIO） as a solvent additive to control the doping density of the PSCs. It is shown that the processing of DIO does not change the doping density of the P3HT phase, while it causes a dramatic reduction of the doping density of the PCBM phase, which decreases the doping density of the whole blend layer from 3.7 × 10^16 cm-3 to 1.2 ×10^16 cm-3. The reduction of the doping density in the PCBM phase originates from the increasing crystallinity of PCBM with DIO addition, and it leads to a decreasing doping density in the blend film and improves the short circuit current of the PSCs.

Effect of Mn substitution on superconductivity in iron selenide (Li, Fe)OHFeSe single crystals

We synthesize a series of Mn substituted （Li, Fe）OHFeSe superconductor single crystals via a modified ion-exchange method, with the Mn concentration z （the atomic ratio of Mn：Se） ranging from 0 to 0.07. The distribution homogeneity of the Mn element incorporated into the lattice of （Li, Fe）OHFeSe is checked by combined measurements of high-angle- annular-dark-field （HAADF） imaging and electron energy-loss spectroscopy （EELS）. Interestingly, we find that the superconducting transition temperature Tc and unit cell parameter c of the Mn-doped （Li, Fe）OHFeSe samples display similar V-shaped evolutions with the increasing dopant concentration z. We propose that, with increasing doping level, the Mn dopant first occupies the tetrahedral sites in the （Li, Fe）OH layers before starting to substitute the Fe element in the su- perconducting FeSe layers, which accounts for the V-shaped change in cell parameter c. The observed positive correlation between the Tc and lattice parameter c, regardless of the Mn doping level z, indicates that a larger interlayer separation, or a weaker interlayer coupling, is essential for the high-Tc superconductivity in （Li, Fe）OHFeSe. This agrees with our previous observations on powder, single crystal, and film samples of （Li, Fe）OHFeSe superconductors.

High-Temperature Performance Analysis of AlGaN/GaN Polarization Doped Field Effect Transistors Based on the Quasi-Multi-Channel Model

We report on the temperature-dependent dc performance of A1GaN/GaN polarization doped field effect transistors （PolFETs）. The rough decrements of drain current and transeonductance with the operation temperature are observed. Compared with the conventional HFETs, the drain current drop of the PolFET is smaller. The transeonductance drop of PolFETs at different gate biases shows different temperature dependences. From the aspect of the unique carrier behaviors of graded AlGaN/GaN heterostructure, we propose a quasi-multi-channel model to investigate the physics behind the temperature-dependent performance of AlGaN/GaN PolFETs.

HALL EFFECT IN NIOBIUM DOPED YBa_2Cu_3O_(7-y) SUPERCONDUCTOR

YBa_2Cu_(3-x)Nb_xO_(7-y) superconductors have been prepared. XRD shows that the system remains orthorhombic for all composition. Substitution of Nb^(5+) for Cu^(2+) occurs in the Cu(2) sites. The introduction of the Nb^(5+) ions produces some extra free-electrons. These electrons recombine with the carriers of the system. It makes the mobility and the Hall number of YBa_2Cu_(3-x)Nb_xO_(7-y) decrease and also result in a depression in Tc.

INFLUENCE OF THE ALIGNMENT OF TiO_2 NANOPARTICLES ON OPTICAL AND STRUCTURAL PROPERTIES OF POLY(PHENYLENEVINYLENE) FILMS

A series of poly(phenylenevinylene) (PPV)/titanium oxide (TiO_2)nanocomposites with different contents of TiO_2 nanoparticles were prepared from mixtures of PPVprecursor and titanium butoxide ethanol solution in a sol- gel process. TEM images showed theformation of the connected network of TiO_2 nanoparticles with a higher content of TiO_2, whichresulted in the titanium butoxide hydrolyzed to form Ti organic compound. Meanwhile, the conjugationof PPV polymer chains can be interrupted by the TiO_2 network structure. The PL spectra revealedthat the emitted light of the PPV/TiO_2 nanocomposites blue shifted without fine structure and thePL intensity enhanced when the TiO_2 network formed. In the lifetime spectroscopy of positronannihilation, the structural properties of the PPV dominated the character of the nanocomposites, inwhich the formation of the omicron -Ps was presented in free volume polymer, when the content ofTiO_2 was below 10 percent. Further increasing the content of TiO_2 nanoparticle introduced muchmore vacancies, vacancy clusters and grain boundaries at their interfaces, which led to thecorresponding lifetime and intensity close to that of the nano- TiO_2 bulk materials. With the TiO_2content of 50 percent of long lifetime. These phenomena suggested that the optical and structuralproperties of the PPV/TiO_2 nanocomposites are dependent on the interfacial structure between PPVand TiO_2 nanoparticles.