Deposition Of Na Research Articles

Insights into Na+/Ca2+ poisoning mechanisms of Zr-modified and unmodified La-Mn perovskite oxide catalysts for NH3-SCR reaction

The presence of alkali metal/alkaline earth metal in fuel gas is one of the important reasons for the deactivation of catalyst for selective catalytic reduction of NOx with NH3 (NH3-SCR). In this work, the Na+/Ca2+ poisoning mechanisms of Zr-modified and unmodified La-Mn perovskite oxides for NH3-SCR reaction were studied. It is found that the deposition of Na+ into LaMnO3 (LM) catalyst has a much larger effect than that of Ca2+, while such a result is opposite for the Na+/Ca2+-deposited La0.8Zr0.2MnO3 (ZLM) catalysts. The deposition of Na+/Ca2+ compounds can block the pores and affect the adsorption and activation of NH3 on the catalysts. After Zr modification, the catalyst with a higher Mn4+ content shows a better redox property and increased acid sites. These acidic sites can trap Na+, thereby delaying the catalyst poisoning and causing a better activity of ZLM catalyst than LM catalyst. The deposition of Ca2+ in the form of CaCO3 on the catalyst surface leads to a serious pore blockage, showing a poor resistance to Ca2+. After regeneration, the pores of the catalyst are dredged, and the active sites originally occupied by Na+/Ca2+ are released, resulting in an recovery of catalyst activity. The recovery of adsorbed oxygen and Mn4+ content is the key factor for returning the SCR activity.

Alkalized MXene/carbon nanotube composite for stable Na metal anodes.

Ti3C2 MXenes are emerging 2D materials and have attracted increasing attention in sodium metal anode fabrication because of their high conductivity, multifunctional groups and excellent mechanical performances. However, the severe self-restacking of Ti3C2 MXenes is not conducive to dispersing Na+ and limits the function of regulating sodium deposition. Herein, an alkalized MXene/carbon nanotube (CNT) composite (named A-M-C) is introduced to regulate Na deposition behavior, which consists of Na3Ti5O12 microspheres, Ti3C2 MXene nanosheets and CNTs. Ti3C2 MXene nanosheets with large interlayer spaces and "sodiophilic" functional groups can provide abundant active sites for uniform nucleation and deposition of Na. Plenty of nanosheets are grown on the surface of the microsphere, thereby reducing the local current density, which can guide initial Na nucleation and promote Na dendrite-free growth. Furthermore, CNTs increase the electrical conductivity of the composite and achieve fast Na+ transport, improving the cycling stability of Na metal batteries. As a result, at a capacity of 1 mA h cm-2, the A-M-C electrode achieves a high average coulombic efficiency (CE) of 99.9% after 300 cycles at 2 mA cm-2. The symmetric cells of A-M-C/Na provide a long cycling life of more than 1400 h at 1 mA cm-2 with a minimal overpotential of 19 mV at an areal capacity of 1 mA h cm-2. The A-M-C/Na//NVP@C full cell presents a high coulombic efficiency of 98% with 100 mA g-1 in the first cycle. The strategy in this work provides new insights into fabricating novel MXene-based anode materials for dendrite-free sodium deposition.

Lignin, cellulose and nutrient deposition in litters of Bambusa vulgaris stands in a regenerating forest in Ile-Ife, Nigeria

The lignin, cellulose and nutrient deposition of litters were assessed in four 0.06 ha plots of Bambusa vulgaris stands in a regenerating forest in Ile-Ife, Nigeria, 35 years after ground fire, with a view to providing information on these parameters which are generally lacking in the forest ecosystem. The collected litters were sorted into leaves and twigs, oven-dried at 70 °C to a constant weight, ground and analysed for lignin, cellulose and nutrients. The total lignin and cellulose content in the litters showed significant (p≤0.05) monthly variation. There was no significant (p ≥ 0.05) difference in the monthly nutrient deposition of Na, Mg, K, Fe, N, P, Mn, Zn and Cu, but there was significant difference in the monthly nutrient deposition of C and Ca through the litter fall fraction (p ≤ 0.05) in the bamboo stands in the secondary rainforest. The depositions of C, N, Ca, Mg and Cu were higher in the bamboo stands but lower in Na, Mn and Zn deposition in 1990 and 2013 studies. The bamboo stands contributed significantly to the carbon sequestration, nutrient dynamics and regeneration status of the forest.

Sodiophilic Zn/SnO2 porous scaffold to stabilize sodium deposition for sodium metal batteries

Sodium is regarded as a promising electrode material in the post lithium ion battery era due to its high theoretical specific capacity of 1166 mAh g−1, low electrochemical potential (−2.71 V vs standard hydrogen electrode), low cost and high natural abundance. However, similar to lithium metal anode, sodium metal anode also shares the problems of uncontrollable dendrites growth, formation of unstable solid electrolyte interface and large volume change during repeated plating/stripping. Herein, a porous sodiophilic zinc metal framework modified with SnO2 surface layer is introduced on copper substrate and used as 3D current collector for sodium metal batteries in order to realize even deposition of Na, moderate the volume change and construct a stable solid electrolyte interface layer simultaneously. Theoretical calculations based on density functional theory are used to interpret the deposition behavior of the metallic Na on different current collectors. The electrochemical performance results show that the Cu/Zn/SnO2@Na symmetric cell can deliver an extremely low nucleation overpotential (0 mV), outstanding long-term rate performance over 1000 h and also can be cycled for around 700 h even at a high current density of 5 mA cm−2 for total capacity of 5 mAh cm−2. Cu/Zn/SnO2@Na//Na3V2(PO4)3 full cell is also constructed to display the feasible application of the designed Cu/Zn/SnO2 porous current collector in advanced sodium metal anode.

Production of high-purity hydrogen from paper recycling black liquor via sorption enhanced steam reforming

Environmentally friendly and energy saving treatment of black liquor (BL), a massively produced waste in Kraft papermaking process, still remains a big challenge. Here, by adopting a NiCaOCa12Al14O33 bifunctional catalyst derived from hydrotalcite-like materials, we demonstrate the feasibility of producing high-purity H2 (∼96%) with 0.9 mol H2 mol−1 C yield via the sorption enhanced steam reforming (SESR) of BL. The SESRBL performance in terms of H2 production maintained stable for 5 cycles, but declined from the 6th cycle. XRD, Raman spectroscopy, elemental analysis and energy dispersive techniques were employed to rationalize the deactivation of the catalyst. It was revealed that gradual sintering and agglomeration of Ni and CaO and associated coking played important roles in catalyst deactivation and performance degradation of SESRBL, while deposition of Na and K from the BL might also be responsible for the declined performance. On the other hand, it was demonstrated that the SESRBL process could effectively reduce the emission of sulfur species by storing it as CaSO3. Our results highlight a promising alternative for BL treatment and H2 production, thereby being beneficial for pollution control and environment governance in the context of mitigation of climate change.

Conducting Polymer Paper-Derived Mesoporous 3D N-doped Carbon Current Collectors for Na and Li Metal Anodes: A Combined Experimental and Theoretical Study

Herein, the manufacturing of a free-standing N-doped mesoporous carbon (CPPY) paper by straightforward carbonization of polypyrrole-coated nanocellulose paper is described. The deposition of Na and...

Cu(In,Ga)Se2 surface treatment with Na and NaF: A combined photoelectron spectroscopy and surface photovoltage study in ultra-high vacuum

Either metallic Na or NaF were deposited onto Cu(In,Ga)Se2 surfaces and studied by photoelectron spectroscopy and surface photovoltage spectroscopy without breaking the ultra-high vacuum. The deposition of elemental Na at room temperature led to the formation of an intermediate Cu and Ga rich layer at the CIGSe surface, whereas for NaF the composition of the CIGSe surface remained unchanged. A metal like surface induced by an inverted near surface region with a reduced number of defect states was formed after the deposition of Na. Under the chosen experimental conditions, the near surface layer was independent on the amount of Na and stable in time. In contrast, the usage of NaF weakened the inversion and led to an increased band bending compared to the untreated CIGSe sample. The SPV signals decreased with proceeding time after the deposition of NaF.

Bismuth–Indium–Sodium two-dimensional compounds on Si(111) surface

Using scanning tunneling microscopy (STM) observations, it has been found that room temperature (RT) deposition of Na onto the (Bi,In)/Si(111) surfaces, namely the 2 × 2 and √7 × √7, induces formation of a joint bismuth-indium-sodium structure without changing of the initial periodicity. For the 2 × 2-(Bi,In), Na atoms “conceal” defects and domain boundaries, while the √7 × √7-(Bi,In) is reconstructed into the new Si(111)√7 × √7-(Bi,In,Na) structure. The first structure is temperature unstable, but the √7 × √7-(Bi,In,Na) is thermostable and can be formed by ordinary codeposition of the metals onto the Si(111)7 × 7 surface followed by annealing at 350–360 °C. Scanning tunneling spectroscopy (STS) has demonstrated that the √7 × √7-(Bi,In,Na) is semiconductor with a ∼0.5 eV energy gap. The structural model of the √7 × √7-(Bi,In,Na) has been proposed on the basis of DFT calculations and comparison of simulated and experimental STM images as well as density of states (DOS) and STS spectra.

Substrate Effects on the Cycleability of Metallic Sodium Electrode in Organic Electrolyte

Sodium (Na) shares similar chemical properties with lithium (Li) in many aspects, and Na has more positive potential, so it should be able to be used in the majority of the organic electrolytes which have been used in Li ion batteries. More importantly, Na is one of the most abundant elements in the Earth’s crust. Therefore rechargeable sodium batteries are the ideal alternative to LIBs [1-3] in many applications. Na-ion batteries (NIBs) consist of sodium intercalation materials for both positive and negative electrodes, which are electronically separated by electrolyte as a pure ionic conductor. Na ions are cycled back and forth from host electrodes, which is similar to LIBs. This design avoids the use of reactive metallic Na. So the research of NIBs is mainly focused on the development of the cathode materials, and the study of the metallic Na electrode has drawn few attentions in the past. As the Li+ deposition-stripping is crucial to LIBs, the nature of the metallic Na, especially electro-deposition-stripping characteristics, is also worthy of in-depth and systematic research. In this work, the electrodeposition and stripping characteristics of metallic Na in the electrolyte of 1 mol L-1 NaClO4/EC+DMC (1:1 vol. %) were studied and the deposition-stripping behavior of Na+ on Cu and Sn substrates were compared. The deposition-stripping cycling performances of Na on the substrates were studied through galvanostatic charge-discharge method and cyclic voltammetry. The morphologies of the substrates before and after Na+ deposition were investigated through digital video microscopy. The kinetics of the Na+ electrodeposition on the different substrates was studied through galvanostatic pulse method. The solid electrolyte interface films of Na+ deposits on the substrates were characterized via electrochemical impedance spectroscopy. The results indicate that the nature of the substrate can significantly affect the electrodeposition characteristics of Na+. The high reactivity of metallic sodium with the organic electrolyte solvents and the dendrite formation during metallic Na deposition are even more problematic than metallic Li anodes. Sn is a more suitable substrate than Cu for Na+ electrodeposition due to the formation of Na—Sn alloy during the deposition of Na+.

Na Deposition on MnO(100)

Na deposition on the MnO(100) surface was investigated by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED). Na TPD and XPS results indicate that adsorbed Na interacts strongly with the MnO substrate to form an irreversibly-adsorbed, oxidic Na compound on the surface for coverages up to 1 monolayer (ML). This strongly-bound Na diffuses into the MnO subsurface and bulk at elevated temperatures above 500K. For Na coverages above 1 ML, metallic Na is present and desorbs from the surface below 500K. The deposition of Na on MnO(100) follows a Stranski–Krastanov (SK) growth mode, with the formation of metallic Na islands following completion of the first Na monolayer. After Na deposition, the surface exhibits a diffuse (1×1) LEED pattern, suggesting the formation of disordered Na overlayers. After heating to 1000K, the surface presents a (2×2) LEED pattern indicating that a surface reconstruction is induced by the diffusion of Na into the near surface region. CO2 can be used as a probe molecule in TPD to distinguish between metallic Na islands and oxidic Na in the first ML, and to indicate when Na that is still observable by XPS goes subsurface.

The Impact of Solute Leaching on the Salt Tolerance during Germination of the Common Roadside Plant Dipsacus fullonum subsp. sylvestris (Dipsaceae)

Variation in salt tolerance during early seedling growth has been reported in seeds of Dipsacus fullonum subsp. sylvestris. Seeds collected from roadside populations displayed a greater salt tolerance than those from old fields; this salt tolerance was highly correlated with seed sodium ion (Na+) content. We hypothesized that the salt tolerance during germination was conferred through the deposition of Na+ in seeds by the maternal plant. To determine the role of Na+, we leached the soluble components from seeds before salt exposure and compared the salt tolerance of leached seeds and unleached seeds. Seeds from maternal families from the roadside showed higher salt tolerance than those from old fields. Leaching the seeds before salt exposure had no effect on the salt tolerance of old field families but caused some roadside families to lose salt tolerance. Roadside populations of D. fullonum appear to possess two distinct salt‐tolerance strategies, osmotic stress tolerance conferred by seed composition and an inherent ability to tolerate highly saline conditions. This study reveals substantial diversity among D. fullonum populations in the roadside environment with variation not only in the ability to tolerate elevated salinity but also in the mechanism.

Mixed Langmuir–Blodgett monolayers containing carboxylic ionophores. Application to Na + and Ca 2+ ISFET-based sensors

Novel ISFET devices coated with ultrathin membranes are suitable for cation detection in liquids. Deposition of Na +-ion and Ca 2+-ion sensitive Langmuir–Blodgett films onto ISFET surfaces has been achieved. In this work, we present first experimental results about ISFET devices coated with LB mixed films. The sensitive material is a carboxylic ionophore (monensin or calcimycin) included in a phospholipid matrix. The sensors showed a linear response with a slope of 19 mV/pNa in the range 10 −2/10 −6 mol/l and a slope 23 mV/pCa in the range of 10 −2/10 −4 mol/l. The results have demonstred the transferability of mixed films onto structured semiconductor devices like ISFETs. This response let us expect further improvements.

RAS: a new probe of surface states

We now have a good understanding of surface states on metal surfaces and a number of occupied and unoccupied surfaces states on low index faces of metal single crystal have been well characterized. Recently a new optical technique, reflection anisotropy spectroscopy (RAS), has been shown to be sensitive to surface states. The RAS technique is briefly described and experimental spectra obtained from the Cu(110) surface are presented. Changes in the RAS of Cu(110) as a result of thermal processing and the induction of the Cu(110) 2×1 phase transition by the deposition of Na can be understood in terms of the associated changes in surface states.

Second-harmonic generation from Na-covered Cu(110): intensity enhancement by inter-surface-state transitions?

Deposition of Na at submonolayer coverage onto Cu(110) at 100 K causes a dramatic increase of second-harmonic intensity generated at the λ=1064 nm fundamental wavelength. Around 0.6 ML the resonance-like enhancement is about three orders of magnitude compared with clean Cu(110). We report on a detailed analysis of the emitted intensities and suggest a model where the intensity resonance around 0.6 ML coverage is driven by transitions between filled and empty electronic surface states. Deposition of Na at 300 K results in a reconstructed surface. Now the intensity resonance observed in SHG is localized at a coverage around 0.3 ML. No clear model emerges for the interpretation. In conclusion, the results indicate a very detailed influence of the adsorption geometry and thus do not support models based on atomic-like intra-adsorbate transitions of alkali-derived orbitals.

Thermal Desorption of Sodium Atoms from Thin SiO2 Films

The adsorption and thermal desorption of Na from thin SiO2 films have been studied. X-ray photoelectron spectroscopy (XPS), angle-resolved XPS (ARXPS), low energy ion scattering (LEIS), temperature-programmed desorption (TPD), low energy electron diffraction (LEED) and work function measurements have been used to characterize the growth mechanism and properties of stoichiometric SiO2 films deposited onto a Re (0001) substrate. Upon deposition of Na onto SiO2 at 250 K, the first monolayer of Na exhibits ionic character, and evidence of metallic Na (plasmon features in XPS) is observed for higher coverages. TPD spectra for Na from SiO2 include a monolayer peak at ~700 K, and the multilayer peak due to sublimation of bulk Na at ~330 K. Penetration of Na into SiO2 can be induced by heating, or by He ion bombardment of a Na/SiO2 layer. The sticking probability for Na on SiO2 is ~0.5 at 250 K, and it decreases at higher substrate temperatures.

THERMAL DESORPTION OF SODIUM ATOMS FROM THIN SiO2 Films

The adsorption and thermal desorption of Na from thin SiO2 films have been studied. X-ray photoelectron spectroscopy (XPS), angle-resolved XPS (ARXPS), low energy ion scattering (LEIS), temperature-programmed desorption (TPD), low energy electron diffraction (LEED) and work function measurements have been used to characterize the growth mechanism and properties of stoichiometric SiO2 films deposited onto a Re (0001) substrate. Upon deposition of Na onto SiO2 at 250 K, the first monolayer of Na exhibits ionic character, and evidence of metallic Na (plasmon features in XPS) is observed for higher coverages. TPD spectra for Na from SiO2 include a monolayer peak at ~700 K, and the multilayer peak due to sublimation of bulk Na at ~330 K. Penetration of Na into SiO2 can be induced by heating, or by He ion bombardment of a Na/SiO2 layer. The sticking probability for Na on SiO2 is ~0.5 at 250 K, and it decreases at higher substrate temperatures.

Exchange reaction between Li and Na intercalated into TiS 2

Single crystals of TiS 2(0001) were intercalated sequentially by Li and Na. The intercalation occurred across the Van der Waals planes, by deposition onto the basal plane of TiS 2. The investigation took place in UHV by soft X-ray photoelectron spectroscopy. Deposition of Na onto Li-intercalated TiS 2(0001) caused the Li to move further into the bulk of the substrate. However, deposition of Li onto Na-intercalated TiS 2(0001) forced Na to move out towards the surface by an exchange mechanism. These interactions between intercalated Li and Na into TiS 2(0001) and their subsequent behaviour have been explained by a correlation of thermodynamic (Gibbs free energy), kinetic (diffusion coefficient) and electrostatic effects.

INTERACTION BETWEEN Li AND Na INTERCALATED INTO 1T-TaSe2 LAYER COMPOUNDS

In this work we study the adsorption of Li on a Na-intercalated TaSe 2(0001) and, reversibly, the deposition of Na on a Li-intercalated TaSe 2(0001) surface. The intercalation occurred by deposition of the alkali elements onto the basal plane of the TaSe 2. The experiment was performed in UHV by soft X-ray photoelectron spectroscopy, using synchrotron radiation as excitation source. Lithium intercalation into 1T-TaSe 2 leads to a phase transition of the substrate from 1T to 2H polytypism. Lithium and sodium appear to compete in the intercalation process. Sodium pushes the preintercalated Li deeper into the bulk of the substrate, whereas, in the case of Li on Na-intercalated TaSe 2, an exchange reaction takes place and part of the Na deintercalates.

Electronic structure of pure and alkali-metal-intercalatedVSe2

The valence bands of the layered compound ${\mathrm{VSe}}_{2}$ and the related intercalation compounds ${\mathrm{Na}}_{x}{\mathrm{VSe}}_{2},$ ${\mathrm{K}}_{x}{\mathrm{VSe}}_{2},$ and ${\mathrm{Cs}}_{x}{\mathrm{VSe}}_{2}$ have been investigated by means of angle-resolved photoelectron spectroscopy, and compared to self-consistent linear augmented plane-wave (LAPW) band calculations. The intercalation compounds were prepared in situ by deposition of Na, K, and Cs on ${\mathrm{VSe}}_{2}$ cleavage surfaces. The intercalation was monitored by core-level spectroscopy, and although K was found to intercalate more slowly than Na and Cs, estimated alkali concentrations of $x=0.2--0.3$ were reached for all three alkali metals. Additional depositions mainly seemed to increase the intercalation depth. Good agreement between LAPW calculations and valence-band spectra was found, in particular for the dispersion along the layers. Normal-emission spectra, obtained at different photon energies, indicated vanishing perpendicular dispersion, but in spectra measured under variation of the emission angle some band-edge signatures were seen, which suggests that some perpendicular dispersion remains, in accordance with the LAPW calculations. The lack of dispersion in the normal-emission spectra could be due to intercalation induced structural transformations, leading to stacking disorder. Also correlation effects may contribute. The rigid-band model is found inadequate, except as a crude approximation, for describing the changes during the initial phase of intercalation. It might be used to describe the continued intercalation, however, under condition that the intercalation modified bands are used. The need for studies that probe both electronic and crystallographic structure (including defects) is stressed.

Na and Cl2 Interaction on it and 2H–TaSe2(0001) Surfaces

In this paper we study the interaction of Cl 2 and Na on 1T– TaSe 2 and 2H– TaSe 2(0001) surfaces in the temperature range of 100–300 K. The experiments are performed in UHV with the use of LEED and SXPS by synchrotron radiation measurements. Deposition of Na on Cl 2-covered 1T– TaSe 2 at 100 K forms initially a [Formula: see text], which with increasing temperature to 300 K leads to NaCl formation. Adsorption of Cl 2 on Na-intercalated 1T and 2H– TaSe 2 surfaces at 100 K forms Cl 2 multilayers. The first Cl 2 layer, in contact with the substrate, interacts with the Na near the surface and forms [Formula: see text]. Warming up to 300 K leads to partial desorption of Cl 2, while the remaining chlorine interacts strongly with Na, causing the deintercalation of Na to the surface in the tendency to form NaCl. The intercalation–deintercalation process takes place across the van der Waals planes and it is much faster on 2H than on 1T– TaSe 2, which is attributed to the different crystal structure of 2H and 1T of TaSe 2.