Ba Adsorption Research Articles

Using Activated Biochar from Caryocar brasiliense Pequi Almonds for Removing Methylene Blue Dye in an Aqueous Solution

Water pollution remains a global problem that urges researchers to develop new technologies aimed at environmental restoration. Here, this study aimed at obtaining an activated biochar from pequi almonds for dye removal. Before and after adsorption, the materials underwent characterization using techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TG). The biochar from the pequi almond was called BA, and the activated biochar from the pequi almond was called ABA. The influence of the pH, contact time, and adsorbate concentration on adsorption was investigated using the dye methylene blue. The morphological assessment revealed higher cracks and pores in the ABA than in the BA. The TG showed that the BA lost approximately 19% more mass than the ABA, indicating that activation occurred. The activation contributed to the decrease in the degree of disorder in the BA because of the increased number of graphitic carbon atoms (ordered) in the ABA, as observed via Raman. The adsorption kinetics followed a pseudo-second-order model, while the adsorption isotherms followed the Langmuir model. The BA adsorption capacity was 500.00 mg g−1, constituting a robust solution for dye removal from aqueous environments. Therefore, this implies the success of the process.

Adsorption of Ba and 226Ra on illite: A comparative experimental and modelling study

Illite, smectite and illite/smectite mixed layers are major phases in various argillaceous rock formations foreseen as potential host rocks for the deep geological disposal of high-level radioactive waste and are important sorbents for cationic radionuclides potentially released in the repository. 226Ra is a critical radionuclide in the safety analysis and an important source of radioactivity in technically enhanced naturally occurring radioactive materials. A comprehensive study was carried out on the adsorption of Ba and Ra on purified homoionic Na-illite (Illite du Puy) over a wide range of experimental conditions (pH, concentration, ionic strength) allowing for the development of a quasi-mechanistic Ba/Ra adsorption model for illite. Ba adsorption isotherms obtained at fixed ionic strength and pH exhibit a non-linear behaviour in the Ba equilibrium concentration range between ∼10−7 and ∼10−2 M. The pH dependent adsorption of trace 226Ra and Ba was investigated at different ionic strengths and evidenced a more pronounced adsorption of 226Ra than Ba on illite. Finally, a competition experiment of trace 226Ra in the presence of increasing Ba concentrations showed an unexpected 226Ra adsorption behaviour which was not observed for montmorillonite in earlier studies. This large set of experimental data could be successfully modelled by Ba/226Ra exchange reactions against Na, together with selectivity coefficients, on two different site types, namely planar sites and high affinity sites. The modelling of the pH dependent adsorption of Ba and 226Ra at high ionic strength and high pH required an additional surface complexation reaction. Two additional exchange sites had to be introduced to quantitatively describe the 226Ra uptake on illite in the 226Ra/Ba competition experiment. The nature of these sites, however, remains unclear. The implementation of the 226Ra adsorption model into predictive transport modelling codes is of key importance for the safety analysis of deep geological disposal of radioactive waste.

Intercalated organo-bentonite as efficient biosorbent for aromatic carboxylic acids from wastewater

This study aims to prepare intercalated organo-bentonite using cetylbenzyldimethylammoniumbromide (CBDAB) and investigate its ability for the removal of benzoic (BA) and salicylic (SA) acids from wastewater. The obtained results confirm the intercalation of CBDA into the bentonite interlayer. Several important parameters of SA and BA adsorption onto sodium bentonite (Na-bent) and intercalated bentonite (CBDA-bent) including the adsorbent dosage, contact time, pH, ionic strength, and temperature are investigated in batch mode. Overall, CBDA-bent, which possesses a high specific surface (32 m2/g) area and a pore volume (0.14 cm3/g) demonstrates promising prospects for SA and BA adsorption, reaching 55.2 mg/g and 64.5 mg/g, respectively. The SA and BA are found to primarily interact well through both surface and interlayer processes in basic media. The equilibrium experimental data have been analyzed by Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms; nonetheless the adsorption is well described by the Langmuir model. The influence of contact time on SA and BA uptake is modeled using pseudo second-order, pseudo first-order, intraparticle diffusion, and Boyd kinetic models. An intraparticle diffusion mechanism is found to control the adsorption process, where the internal mass transfer is higher than the external mass transfer. A thermodynamic study shows that the adsorption of both acids is not spontaneous and endothermic. Desorption of SA and BA acids from both Na-bent and CBDA-bent has been performed and the possibilities for reuse investigated.

Retention behaviour of Ba(II) on argillaceous rocks of Cuddapah system

Argillaceous rock formation of Cuddapah System are under evaluation as the potential host rock for deep geological repository in India. Sorption of Ba(II), as a chemical analogue of 90Sr, on argillaceous rock formation has been investigated by batch sorption method. The effect of pH, ionic strength and [Ba(II)] on Ba(II) sorption has been investigated. Ba(II) sorption was found to be independent of pH and decreased with increasing ionic strength, indicating ion exchange as dominant sorption mode for Ba(II). Ba(II) adsorption isotherm was linear up to [Ba(II)] = 3.0 × 10–6 M. Ba(II) sorption was successfully modeled using surface complexation modeling.

Removal of Barium from Solution by Natural and Iron(III) Oxide-Modified Allophane, Beidellite and Zeolite Adsorbents.

Efficient capture of barium (Ba) from solution is a serious task in environmental protection and remediation. Herein, the capacity and the mechanism of Ba adsorption by natural and iron(III) oxide (FeO) modified allophane (ALO), beidellite (BEI) and zeolite (ZEO) were investigated by considering the effects of contact time, temperature, pH, Ba2+ concentration, adsorbent dosage, the presence of competitive ions and adsorption–desorption cycles (regenerability). Physicochemical and mineralogical properties of the adsorbents were characterized by XRD, FTIR, SEM with EDX and N2 physisorption techniques. The Ba2+ adsorption fitted to a pseudo-first-order reaction kinetics, where equilibrium conditions were reached within <30 min. BEI, ALO and ZEO with(out) FeO-modification yielded removal efficiencies for Ba2+ of up to 99.9%, 97% and 22% at optimum pH (pH 7.5–8.0). Adsorption isotherms fitted to the Langmuir model, which revealed the highest adsorption capacities for BEI and FeO-BEI (44.8 mg/g and 38.6 mg/g at 313 K). Preferential ion uptake followed in the order: Ba2+ > K+ > Ca2+ >> Mg2+ for all adsorbents; however, BEI and FeO-BEI showed the highest selectivity for Ba2+ among all materials tested. Barium removal from solution was governed by physical adsorption besides ion exchange, intercalation, surface complexation and precipitation, depending mainly on the absorbent type and operational conditions. BEI and FeO-BEI showed a high regenerability (>70–80% desorption efficiency after 5 cycles) and could be considered as efficient sorbent materials for wastewater clean-up.

Novel hybrid multifunctional composite of chitosan and altered basalt for barium adsorption: Experimental and theoretical studies

Herein, the starting low‒cost and eco‒friendly weathered basalt (WB) was found to be rich in zeolite and clay minerals, which have wide applications in water purification. WB was chemically activated by hydrogen peroxide (H2O2) followed by the interaction with chitosan (Ch) to fabricate a new hybrid composite (WB/Ch) with multifunctional groups. The resulted WB/Ch composite was characterized by XRD, FTIR, SEM, and applied for Ba (II) adsorption at pH 5.0 and different temperatures (i.e., 25, 35 and 45 °C). The adsorption data were fitted to kinetics, classical (Langmuir, Freundlich and Dubinin–Radushkevich) as well as advanced statistical (multilayer) models. The adsorption data of Ba(II) onto WB/Ch were described well by the pseudo-second-order and the applied traditional equilibrium models. The monolayer adsorption capacity (qmax = 45.78 mg g−1) reflected the high removal efficiency of WB/Ch for Ba(II) uptake as compared to varied natural and synthetic adsorbents. Steric and energetic parameters of the multilayer model were interpreted to understand the interaction mechanism between the Ba(II) ions and WB/Ch active sites. Theoretical number of receptor sites (n) was less than unity at all temperatures revealing multi–docking adsorption mechanisms. Interaction between Ba(II) and WB/Ch of the first layer played the principle role in increasing the adsorption capacities (Qsat) from 115.06–128.86 mg g‒1 within the temperature range of 25–45 °C. The total adsorbed Ba(II) layers (the Nt parameter) decreased from 2.79 to 2.02 with temperature thus reflecting its insignificant role to determine the Qsat values. The calculated adsorption energies varied from 22.35 to 28.56 kJ mol‒1 indicated that the Ba(II) adsorption onto the WB/Ch composite was endothermic and related to physical forces. Thermodynamic parameters including Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) reflected the endothermic and spontaneous nature of Ba(II) adsorption process.

Synchrotron radiation photoemission study of Ba adsorption on the vicinal SiC(111)-8° surface

The electronic structure of the Ba/SiC(111)-8° interface has been studied in detail in situ in an ultrahigh vacuum using synchrotron radiation photoelectron spectroscopy. The SiC(111)-8° samples were grown by an original method of epitaxy of low-defect unstressed nanoscaled silicon carbide films on silicon substrates. The Si 2p, C 1s core level spectra have been investigated as a function of Ba submonolayer coverage with photon energies in the range of 100–450 eV. Upon Ba adsorption, a drastic change in the C 1s spectrum was revealed. It was found that Ba adsorption leads to the formation of a new, previously unknown carbon-based structure of C nanoclusters on the surface. Experimental data show that the nanoclusters can be created exclusively on the vicinal SiC(111)-8° surfaces in the presence of stabilizing adsorbed metal atoms, specifically, Ba atoms. It is shown that the surface nanoclusters are formed due to the local interaction between silicon vacancies, carbon atoms and Ba adatoms. It is established that the carbon clusters are composed of carbon rings and their chemical bonds are similar in nature to the bonds in aromatic-like compounds.

Area-Selective Atomic Layer Deposition of Crystalline BaTiO3

Patterned, crystalline BaTiO3 (BTO) films were formed directly on STO(001) surfaces using atomic layer deposition and restricting Ba and Ti precursor adsorption to STO(001) by passivating regions of the substrate with a polystyrene blocking layer. Patterns were prepared by spin-coating polystyrene onto STO(001), UV-crosslinking the polystyrene, and rinsing away uncrosslinked polystyrene with toluene. Amorphous 9–12 nm thick BTO films were deposited at 225 °C on polystyrene-patterned STO(001) surfaces. These films were crystallized upon annealing at elevated temperatures. Atomic force microscopy, scanning electron microscopy, and time of flight secondary ion mass spectroscopy were used after growth of BTO and removal of polystyrene resist and reveal BTO features with dimensions similar to the shadow mask. Reflection high-energy electron diffraction and X-ray diffraction show that BTO epitaxially crystallizes to the substrate, forming BTO(001), after annealing under vacuum at ≥770 °C with an oxygen partial ...

Carbon-Based Aromatic-Like Nanostructures on the Vicinal SiC Surfaces Induced by Ba Adsorption

The electronic structure of the SiC/Si(111)-8° and SiC/Si(111)-4° epitaxial layers with adsorbed Ba submonolayers is thoroughly studied in situ in ultrahigh vacuum by synchrotron-based photoemission spectroscopy. The SiC epitaxial layers were grown on the vicinal Si(111)-8°, Si(111)-4° surfaces by the original method of substitution of atoms. The C 1s and Si 2p сore level spectra are investigated in relation to the different Ba coverages. A substantial change in the C 1s spectra induced by Ba adsorption is revealed. It is found that the effect results from the formation of a new, previously unknown carbon-based structure consist of nanoclusters on the surface. Experimental data show that the nanoclusters can be created exclusively on the vicinal SiC surfaces in the presence of stabilizing adsorbed metal atoms, specifically, Ba atoms. Density functional theory using the basis of plane waves with the pseudopotential approximation is applied to calculate the spatial configuration of this clusters structure. It is shown that the surface nanoclusters are formed due to local interaction between silicon vacancies, carbon atoms and Ba adatoms. It is established that the carbon clusters is composed of carbon rings, in which the chemical bonds are close in nature to the bonds inherent in aromatic-like compounds.

Effects of the Ba Impregnation on Pt Electrode on NO Electrochemical Reduction Mechanism

The study investigated the electrochemical reduction performances of NO and O2 on Pt symmetric electrode with Ba adsorption layer. The temperature varied from 350°C to 550°C. The experimental Ba (NO3)2 solution was impregnated in the Pt electrode. For the NO performance, the polarization curves and CV tests showed that the Pt-BaO electrode showed higher electrochemical performance than Pt electrode. EIS results revealed that the Pt-BaO electrode exhibited higher activity than the Pt electrode. It was due to the decreased polarization resistance in the low-frequency region that dominated the electrochemical impedance spectra. The increase of temperature strengthened the effect of adsorption layer on NO electrochemical performance. The EIS results were fitted well with the equivalent circuit model indicating that the improved mechanism with the Ba adsorption layer may be related with the NO oxidation to NO2 on the Pt surface, the formation of Ba (NO3)2 in the adsorption layer and the reduction of the reaction path from the direct Ba (NO3)2 decomposition.

Soft X-ray photoemission study of Ba adsorption on the ceramic multiferroic BiFeO3

Electronic structure of the ceramic multiferroic BiFeO3 and ultrathin Ba/BiFeO3 interface was studied in situ using photoelectron spectroscopy with energies in the range of 120–900 eV. The photoemission from the Bi 4f, O 1s, Fe 2p, and Ba 4d core levels was studied. An effect of Ba adsorption is found to induce a significant change in all spectra that is originated from the strong interaction with the charge transfer between Fe, O, Bi surface atoms and Ba adatoms. The recharge between Fe3+↔ Fe2+ ions in surface region induced by Ba adsorption is found that provide enhancing the ferroelectric polarization gain.

Surface reconstruction switching induced by tensile stress of [formula omitted] steps: From Ba/Si(0 0 1)-[formula omitted] to Ba/Si(0 0 1)-4° off-[formula omitted

The alkaline-earth metal adsorption on Si(001) has attracted much interest for finding a proper template in the growth of high-κ and crystalline films. Up to now on the flat Si(001) surface with double domains and single-layer steps, the adsorbed Ba atoms are known to induce the 2×3 structure through removing two Si dimers and adding a Ba atom per unit cell in each domain. In the present investigation, the Si(001)-4° off surface with DB steps and single domains has been employed as a substrate and the reconstruction at the initial stage of Ba adsorption has been investigated by scanning tunneling microscopy and synchrotron photoemission spectroscopy. On this vicinal and single domain terrace, a novel 3×2 structure rotated by 90° from the 2×3 structure has been found. Such a 3×2 structure turns out to be formed by adding a Ba atom and a Si dimer per unit cell. This results from the fact that the adsorbed Ba2+ ions with a larger ionic radius relieve tensile stress on the original Si dimers exerted by the rebonded atoms at the DB step.

Soft X-ray photoelectron spectroscopy of the ultrathin Ba/InGaN interface

Electronic structure of the clean In0.22Ga0.78N surface and the ultrathin Ba/In0.22Ga0.78N interface has been studied in situ by the synchrotron-based photoelectron spectroscopy during excitation in the photon energy range of 100–650eV. Changes in the valence band and surface states spectra and in the In 3d, In 4d, N 1s, Ga 3d, Ba 4d, Ba 5p core levels spectra have been investigated under the step-by-step Ba submonolayer deposition. Changes in the surface electronic structure of the InGaN caused by Ba adsorption are found to originate predominantly from the local interaction of the Ga and In dangling bonds and Ba adatoms that results in effect of the suppression of the two intrinsic surface states and appearance of a new induced state. The Ba atomic layer deposition is revealed to induce the charge transfer between the Ba adatoms and the N surface atoms with increasing N-ionicity.

Analysis of barium retention mechanisms on calcium silicate hydrate phases

Calcium silicate hydrate (C-S-H) phases mostly contribute to contaminant retention in cement. The adsorption mechanisms of Ba on C-S-H phases with four different Ca/Si ratios were investigated by batch sorption experiments. The sorption kinetics, the effects of the solid to liquid ratio and the presence of alkalis in solution were analysed. Sorption isotherms in a wide range of Ba concentrations (from 10−10 to 1·10−1M) were performed.To understand the underlying retention mechanisms, the effects of Ba adsorption on surface potentials were additionally examined. The main objective of this study was to develop a sorption model able reproducing not only the Ba sorption behaviour, but also the C-S-H surface potential before and after Ba uptake. The reactions and model parameters selected for satisfying these conditions are discussed in the paper. A three-site model, with weak and strong silanol sites and one exchange site, which satisfactorily fulfils the initial aims, is proposed.

Soft x-ray photoemission spectroscopy of the Ba atomic layer deposition on the ceramic multiferroic BiFeO3

Electronic structure of the ceramic multiferroic BiFeO3 and the Ba/BiFeO3 nanointerface is investigated in situ in an ultrahigh vacuum by synchrotron-based photoemission spectroscopy with the excited photon energy from 120eV to 900eV. The Bi 4f, O 1s, Fe 2p, and Ba 5p core-levels spectra are studied. The Ba atomic layer deposition is found to induce a significant change in spectra that is originated from the charge transfer between Ba adatoms and Bi, O surface atoms with increasing the Bi-valency and O-ionicity. The Fe 2p3/2 core level spectrum for the clean BiFeO3 is shown to contain both the Fe2+ and Fe3+ ion components with the atomic ratio of Fe2+/Fe3+ ∼1. The Ba adsorption is found to increase the ratio up to ∼1.5. This new effect is clearly caused by recharge between Fe3+↔Fe2+ ions with increasing the amount of Fe2+ ions.

Can liming reduce barium uptake by agricultural plants grown on sandy soil?

AbstractUptake of barium (Ba) from soil by vascular plants varies among species. Despite the toxicity of soluble Ba compounds to plants, research on mechanisms controlling Ba uptake from natural soils is scarce. This study investigated the treatment effect of lime (CaCO3) added to a sandy soil containing a total of 500 mg Ba kg−1 on uptake and interspecies distribution of Ba in legumes and other cultivated food and feed plants. Nine species of grasses, vegetables, herbs, and legumes were cultivated under controlled conditions in a greenhouse experiment. The plants were harvested at maturity or flowering, dried, milled, and digested with nitric acid using the microwave technique prior to ICP‐MS analysis. All plant species acquired Ba from the soil in considerable amounts, probably due to low Ba adsorption potential of the sandy soil. Shoot tissue concentrations ranged from about 100 (grass) to 600 mg Ba kg−1 (legume) and root concentrations from about 100 (tuber vegetable) to 700 mg kg−1 (legume). Vicia cracca L. (bird vetch) showed an accumulation capacity due to high shoot concentrations of Ba compared to the other species. Higher yield accompanied by a potential dilution effect can partly explain why Trifolium repens L. (white clover), Pisum sativum ssp. arvénse L. (gray pea) and Hordeum vulgare L. (barley) did not display the highest Ba concentrations, but showed the highest Ba uptake from soil. High plant uptake of calcium (Ca) also seemed to enhance Ba uptake, by legumes in particular. However, liming reduced shoot Ba concentrations, particularly of species with low affinity for Ca. The risk of Ba accumulation thus raises toxicity concerns when forage legumes are cultivated in soils containing elevated concentrations of Ba.

Heterogeneous Nucleation and Growth of Barium Sulfate at Organic-Water Interfaces: Interplay between Surface Hydrophobicity and Ba(2+) Adsorption.

Barium sulfate (BaSO4) is a common scale-forming mineral in natural and engineered systems, yet the rates and mechanisms of heterogeneous BaSO4 nucleation are not understood. To address these, we created idealized interfaces on which to study heterogeneous nucleation rates and mechanisms, which also are good models for organic-water interfaces: self-assembled thin films terminated with different functional groups (i.e., -COOH, -SH, or mixed -SH & COOH) coated on glass slides. BaSO4 precipitation on coatings from Barite-supersaturated solutions (saturation index, SI, = 1.1) was investigated using grazing-incidence small-angle X-ray scattering. After reaction for 1 h, a little amount of BaSO4 formed on hydrophilic bare and -COOH coated glasses. Meanwhile, BaSO4 nucleation was significantly promoted on hydrophobic -SH and mixed -SH & COOH coatings. This is because substrate hydrophobicity likely affected the interfacial energy and hence thermodynamic favorability of heterogeneous nucleation. The heterogeneous BaSO4 nucleation and growth kinetics were found to be affected by the amount of Ba(2+) adsorption onto the substrate and incipient BaSO4 nuclei. The importance of Ba(2+) adsorption was further corroborated by the finding that precipitation rate increased under [Ba(2+)]/[SO4(2-)] concentration ratios >1. These observations suggest that thermodynamic favorability for nucleation is governed by substrate-water interfacial energy, while given favorable thermodynamics, the rate is governed by ion attachment to substrates and incipient nuclei.

Synchrotron-radiation photoemission study of the ultrathin Ba/3C–SiC(111) interface

Electronic structure of the Ba/3C–SiC(111) interface has been detailed studied in situ in an ultrahigh vacuum using synchrotron radiation photoemission spectroscopy with photon energies in the range of 100–450eV. The 3C–SiC(111) samples were grown by a new method of epitaxy of low-defect unstressed nanoscaled silicon carbide films on silicon substrates. Valence band photoemission and both the Si 2p, C 1s core level spectra have been investigated as a function of Ba submonolayer coverage. Under Ba adsorption two induced surface bands are found at binding energies of 2eV and 6eV. It is obtained that Ba/3C–SiC(111) interface can be characterized as metallic-like. Modification of both the Si 2p and C 1s surface-related components were ascertained and shown to be provided by redistribution effect of electron density between Ba adatoms and both the Si surface and C interface atoms.

Effects of Ba Adsorption Layer on NO Electrochemical Reduction Reaction Mechanism

This study investigated the electrochemical reduction of NO and O2 on Pt symmetric electrode by adding NOx adsorbents for the removal of NO from the exhausts of diesel engine or gasoline engine. O2 is excess when compared with NO. Thus, a large mount of external electric field should be consumed by electrochemical decomposition of O2 which gives rise to a low selectivity towards NO. Electrochemical reduction of NO has confronted with the difficult of improving NO selectivity in NO/O2 mixtures. Two cells were prepared and tested: single Pt electrode, Pt electrode with Ba(NO3)2 impregnation. Linear sweep voltammetry(0V~2V), cyclic voltammetry(CV:0.5V~-0.5V) and electrochemical impedance spectroscope(EIS) measurements were carried out between 350℃ and 550℃. The Pt electrode was covered with fine particles on the impregnated electrode surface by scanning electron microscope(SEM). It could be observed from the polarization curves that the Ba impregnated electrode showed higher electrochemical performance than the single Pt electrode especially at low temperatures and high voltages (1.25V to 2V). It can be obtained from the CV tests that the Ba impregnated electrode was superior to the Pt electrode in 800ppm NO. When scanned from 0.5V to -0.5V, the electrochemical performance of NO with O2 was far better than NO especially at high voltages and was close to the performance of O2. While changed the sweep direction backward, NO showed the best electrochemical performance than NO with O2 and O2 near open circuit voltage. EIS results at open circuit voltage revealed that the Ba impregnated electrode exhibited lower resistance than the single Pt electrode due to the decreased polarization resistance in the low-frequency region that dominated the impedance spectra in all atmospheres. The polarization resistances in 800ppm NO showed the smallest while in 8% O2 showed the largest in both electrodes possibly resulted from the generated NO2 formed by NO oxidation on Pt sites, the storage of NOx in the form of Ba(NO3)2 in active sites or the direct electrolysis of Ba(NO3)2 in external electric field that enhanced the reactivity and selectivity of NO reduction. From the impedance analysis using by equivalent circuit model R(CR)(CR)(CR) consisted of serial resistance Rs(related with the conductivity of the electrolyte) and 3 (CR) elements. Results showed that the activation energy of Rs for the two electrodes were nearly the same. The activation energy of the total polarization resistance Rp­ for the Ba impregnated electrode and Pt electrode were 0.874eV and 1.396eV respectively in 800ppm NO and 8% O2. The results were very close to the results obtained in the pure 8% O2 atmosphere. And the activation energy were 0.92eV and 1.50eV for the Ba impregnated electrode and Pt electrode. This was very close to the results of O2 reduction on Pt electrode conducted by Bauerle[1] with the activation energy between 1.43eV and 1.78eV demonstrated that the dissociative adsorption of O2 can be the controlling reaction step. The activation energy in the low frequency(0.01Hz-2Hz) for the three electrodes were close to the results showed by Bauerle resulted from the adsorption, surface diffusion, transfer of O2 and NOx intermediates near/at the triple phase boundary(TPB) and the dissociative adsorption of O2 [1]. The activation energy for the Ba impregnated electrode and Pt electrode in the high frequency were 0.608eV and 0.646eV respectively. The high frequency arc indicated the diffusion of oxide ions to the electrode/electrolyte interface and charge transfer of oxide ions from electrode/electrolyte interface to the electrolyte[2-3]. The activation energy in the middle frequency may be attributed to the charge transfer reactions in the electrode and the dissociative adsorption of O2. And the activation energy were 0.657eV and 1.06eV for the Ba impregnated electrode and Pt electrode. Results showed that the Ba impregnated electrode exhibited lower activation energy in middle and low frequency region indicating the improvement mechanism. Reference [1]J.E. Bauerle, J. Phys. Chem. Solids, 30, 2657 (1969). [2]M. J. Jørgensen, M. Mogensen, J. Electrochem. Soc., 148, A438 (2001). [3]M. L. Traulsenz, K. K. Hansen, J. Electrochem. Soc., 158, P156 (2011). Figure 1

Initial growth of Ba onGe(001): An STM and DFT study

An ordered alkaline-earth submonolayer on a clean $\mathrm{Si}(001)$ surface provides a template for growth of the atomically sharp, crystalline Si-oxide interface that is ubiquitous in the semiconductor device industry. It has been suggested that submonolayers of Sr or Ba on $\mathrm{Ge}(001)$ could play a similar role as on structurally identical $\mathrm{Si}(001)$, overcoming known limitations of the $\mathrm{Ge}(001)$ substrate such as amorphization of its oxidation layers. In this paper the initial stage of the Ba oxidation process, i.e., adsorption and organization of Ba atoms on the $\mathrm{Ge}(001)$ surface as a function of temperature $(270\ensuremath{-}770\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ for coverage 1.0 monolayer (ML) and $0.15\ensuremath{-}0.4\phantom{\rule{0.16em}{0ex}}\mathrm{ML}$, is studied using scanning tunneling microscopy (STM) and density functional theory (DFT). Three types of features have been identified on the Ba-covered $\mathrm{Ge}(001)$ surface. They originate from isolated Ba adatoms, isolated Ba ad-dimers, and the Ba ad-dimers assembled into short-range, randomly distributed chains that run across the Ge dimer rows. We find from both STM measurements and DFT calculations that the latter is the dominant structure on $\mathrm{Ge}(001)$ with increasing coverage.