Oxidant Formation Potential Research Articles

Energy recovery alternatives for the sustainable management of olive oil industry waste in Australia: life cycle assessment

Over the last two decades, the olive oil industry in Australia has been growing at an annual rate of 9%. Nevertheless, the highly polluting solid waste and wastewater generated by the industry poses significant challenges for the environmental sustainability of the industry. This paper analysed five alternatives for managing this waste stream using life cycle assessment methodology. The options included manufacturing briquettes as solid fuel for home heating; pellets for domestic or industrial water heating; pyrolysis and composting. The functional unit used in this study is the processing of 1 Mg of olive solid waste at the mill. Emissions were categorised into eight impact categories: ozone layer depletion potential (ODP), global warming potential (GWP100), eutrophication potential (EP), acidification potential (AP), human toxicity (HTP), fossil fuel depletion potential (FDP), ionising radiation potential (IRP), and photochemical oxidant formation potential (POFP). The study showed that although composting (current best practices – CBP) can achieve significant environmental benefits, using the olive waste to produce energy products may achieve better results, especially when displacing electricity from the main grid. The production of pellets for use in domestic hot water boilers (PHWH) is the option that is likely to deliver the highest environmental benefits. For example, GWP100 and ODP of the PHWH were estimated to be −1057 kg CO2-Eq, −1.5 × 10−5 kg CFC-11-Eq compared to −12.4 kg-CO2-Eq and 5.3 × 10−8 kg CFC-11-Eq achieved by the CBP, respectively. Future energy scenario and transportation distances were identified as significant parameters affecting the performance of the options. Sensitivity analysis showed that the expected change in the future Australian energy mix to cleaner energy sources is unlikely to have a significant effect on the performance of the alternatives. The results also showed little sensitivity to transportation distances of the energy product to the end user. This paper is the first to evaluate options for energy utilisation of olive solid waste using life cycle assessment and compare it to industry current best practices (composting). Although the paper focuses on the Australian olive oil industry, the results are also relevant to other countries and regions were olive solid waste is generated in relatively moderate quantities but distributed over large geographic area.

The LCA of portland cement production in China

Cement production is associated with a considerable environmental load, which needs to be fully understood before effective measures can be taken. The existing literature did not give detailed life cycle assessment (LCA) study of China and had limited potential for investigating how best available techniques (BATs) would provide a maximum benefit when they are applied in China. Japan was selected as a good example to achieve better environmental performance of cement production. We identified potentials for reducing emissions and saving energy and natural resources in Chinese cement industry through the comparative analysis. This paper follows the principal of Life Cycle Assessment and International Reference Life Cycle Data System (ILCD). The functional units are “1 t of portland cement” and with 42.5 MPa of strength grade. The input (limestone, sandstone, ferrous tailings, coal, and electricity) and output (CO2 from limestone decomposition and coal combustion, NOx, PM, and SO2) of cement manufacturing were calculated by use of on-site measurements, calculation by estimated coefficients, and derivation by mass and heat balance principle. The direct (cement manufacturing) and indirect (electricity production) LCI are added to be total LCI results (cement production). The impact categories of global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), photochemical oxidant formation potential (POCP), and human toxicity potential (HTP) are used to calculate environmental impact. Only in GWP of cement manufacturing China has advantage. Japanese cement industry shows remarkable superiorities in the environmental impacts of AP, POCP, HTP, and EP due to advanced technologies. SO2 emissions make the corresponding AP and HTP. PM emissions result in part of HTP. The NOx emissions are the major contributors of POCP, AP, EP, and HTP in China. China emits fewer CO2 emissions (2.09 %) in cement manufacturing than Japan but finally makes higher total GWP than Japan due to more GWP of electricity generation in power stations. The waste heat recovery technology can save electricity but bring more coal use and CO2 emissions. The alternative fuel and raw materials usage and denitration and de-dust technologies can relieve the environmental load. Using the functional unit with the strength grade, the life cycle impact assessment (LCIA) results are affected. LCA study allows a clear understanding from the view of total environmental impact rather than by the gross domestic product (GDP) unit from an economic development perspective. In an LCA study, the power generation should be considered in the life cycle of cement production.

Life Cycle Assessment of Heavy-Duty Truck for Highway Transport in China

The detailed life cycle assessment of heavy-duty truck for highway transport in China is conducted by Centre of National Material Life Cycle Assessment (CNMLCA). The input of energy and output of pollutants emissions are documented as the life cycle inventory (LCI). The life cycle impact assessment (LCIA) results calculated with the CML method show that the hotspot of environmental impacts from transport in China. The environmental benefits from implementations of European emissions standards in China for transport are also analyzed. The analysis shows that the acidification potential (AP) makes the most huge contribution to total environmental impact, up to 33.7%. As the second hotsopt, global warming potential (GWP) takes up 26.83% of total environmental impact. Photochemical oxidant formation potential (POCP) takes up 23.42% of total environmental impact, which is more or less the same comparing with the result of GWP. Eutrophication potential (EP) takes up 15.05% of total environmental impact. The last but not the least environmental impact category - human toxicity potential (HTP), only takes up 0.95% of total environmental impact. If the heavy metal and dioxin emissions are also considered, maybe the results will be changed and the HTP will take more in the whole environmental impact. It can be concluded that if we pay more attention on SO2emissions especially NOx emissions reduction, the acidification and photochemical smog would be relieved a lot and the total environmental impact can be decreased a lot. More punishment on overload may be a good choice to reduce environmental load of heavy truck of highway transport in China.

Life cycle assessment of natural gas combined cycle integrated with CO2 post combustion capture using chemical solvent

In light of global warming consequences and the need to take drastic steps to reduce its impact by capturing the CO2 from stationary sources, environmental performance assessment of CO2 capture processes is vital for deploying existing or innovative capture technologies. Life cycle assessment (LCA) methodology was used in this study to evaluate the impacts associated with CO2 capture from a natural gas combined cycle power plant, by using a scientific approach of process design and sizing of important unit operations. The environmental assessment was conducted for 90% and 80% CO2 capture efficiencies, using conventional monoethanolamine (MEA) and advanced solvent (KS-1), at various CO2 compression configurations. The results show a major reduction in greenhouse gas emission (GHG) for both capture efficiencies. For the 90% CO2 capture efficiency with conventional MEA, a reduction of 76% in GHG emission was achieved for the entire compression configuration. The 80% CO2 capture efficiency with conventional MEA, on the other hand, showed a 65% reduction in GHG emission. Using the KS-1 solvent resulted in a 78% reduction in GHG emission due to reduction in energy required for CO2 regeneration.However, the assessment shows that CO2 capture operations has led to an increase in other environmental impacts such as human toxicity potential, abiotic depletion, marine eutrophication potential, fresh water aquatic ecotoxicity, marine aquatic ecotoxicity, acidification, terrestrial ecotoxicity and photochemical oxidant formation potential. These impacts are mainly due to the additional energy required for the CO2 capture, infrastructures and chemical solvent used. The advantage of using the novel solvent (KS-1) is clear at 90% CO2 capture compared to the conventional MEA solvent.

Regression modeling of field emissions in wheat production using a life cycle assessment (LCA) approach

Field emissions of Irianian wheat production were investigated. Data were collected from 260 farms from the city of Fereydonshahr in the Esfahan province. Life cycle assessment (LCA) methodology was developed to assess environmental impacts associated with the production of wheat in the studied region. Global warming potential (GWP), eutrophication potential (EP), human toxicity potential (HTP), terrestrial eco-toxicity potential (TEP), oxidant formation potential (OFP) and acidification potential (AP) were calculated as 2620.86 kg CO2 eq.t-1 (tonne of grain), 14.25 kg PO4-2 eq.t-1, 1111.7 kg 1,4-DCB eq.t-1, 10.59 kg 1,4-DCB eq.t-1, 0.0073 kg ethylene eq.t-1 and 19.07 kg SO2 eq.t-1, respectively. In order to specify a relationship between input materials and field emissions (direct and indirect emission), the Cobb-Douglass production function was applied. The impacts of farm area, N, P2O5, K2O, diesel fuel and biocides were entered as independent variables and different impact categories as dependent variables. RMSE of models for GWP, EP, HTP, TEP, OFP and AP was 0.07, 0.19, 0.17, 0.34, 0.49 and 0.26, respectively. Accordingly with a rise in farm size level, the emissions per tonne of grain produced decreased. Accordingly, large farms are more environmentally friendly due to more yields and less emissions per tonne of grains.

Prognostication of environmental indices in potato production using artificial neural networks

Abstract Artificial Neural Network (ANN) is an appropriate tool for forecasting the non-linear relationships across many scientific studies. In this study a back-propagation (BP) learning algorithm was chosen to predict the environmental indices of potato production in Iran. Data were collected randomly from 260 farms in Fereydonshahr city, located in Esfahan province by face to face questionnaire method. Initially, Life cycle assessment (LCA) methodology was developed to assess all the environmental impacts associated with potato cultivation in the studied region. The six LCA indices including global warming potential (GWP), eutrophication potential (EP), human toxicity potential (HTP), terrestrial ecotoxicity potential (TEP), oxidant formation potential (OFP) and acidification potential (AP) were selected as target outputs. Farm gate and one tone of potato produced were chosen as system boundary and functional unit. To find the best topology, several ANN models with different number of hidden layers and neurons in each layer were developed. To assess the best performance, a topology with highest coefficient of determination ( R 2 ), lowest root mean square error (RMSE) and mean absolute error (MAE) was selected as optimum architecture. Accordingly, ANN model with 11–10–6 structure showed the best performance. RMSE for GWP, HTP, EP, OFP, AP and TEP was computed as 0.037, 0.005, 0.057, 0.032, 0.048 and 0.037, respectively. Also, MAEs for this model were calculated as 0.028, 0.001, 0.039, 0.022, 0.035 and 0.027 for GWP, HTP, EP, OFP, AP and TEP, respectively. Evaluation of the results revealed that the developed ANN model (11–10–6 architecture) appears to be appropriate tool in predicting environmental indices of potato production.

Role of Cerium Oxide in the Enhancement of Activity for the Oxygen Reduction Reaction at Pt–CeOxNanocomposite Electrocatalyst - An in Situ Electrochemical X-ray Absorption Fine Structure Study

In situ electrochemical X-ray absorption fine structure (XAFS) measurements were performed at the Pt L3 and Ce L3 edges of the Pt–CeOx/C catalyst, which was prepared by a combined process of precipitation and coimpregnation methods, as well as at the Pt L3 edge of the conventional Pt/C catalyst in oxygen-saturated H2SO4 solution to clarify the role of CeOx in the reduction of the overpotential for the oxygen reduction reaction (ORR) at the Pt–CeOx nanocomposite compared with the conventional Pt/C catalyst. XAFS measurements clearly show that the enhancement of ORR activity is attributed to the inhibition of Pt oxide formation by the CeOx layer, of which Ce3+ was oxidized to Ce4+ instead of Pt at the Pt oxide formation potential.

Anodizing and corrosion behaviour of aluminium

In this study, aluminum was anodized in 0.4 M H2SO4 + 0.145 M H3BO3 solution by means of potentiostatic method. In first step, the most appropriate conditions (anodizing voltage and period) were determined. The voltage-current behavior was investigated between 0 to 30 V and oxide formation potential (15 V) was determined. Then chorono-amperometric measurement was obtained at this potential during 2 hours. Therefore, anodizing process was applied at 15 V between aluminium anode and mild steel cathode. In the second step, the corrosion performance of non-anodized (Al) and anodized samples (Al2O3) have been investigated in 3.5% NaCl solution by using electrochemical impedance spectroscopy and polarization techniques. The interface between metal and solution was modeled with the equivalent circuit successfully. The circuit’s elements were calculated with Ivium Soft fitting program. The polarization curves were obtained between −1.8 V and 0.5 V potential ranges. The experimental results proved that the thickness and quality of oxide film was improved with help of anodizing process. Thus the corrosion resistance of anodized aluminum is significantly increased.

Assessment of Platinum Dissolution from a Pt/C Fuel Cell Catalyst: An Electrochemical Quartz Crystal Microbalance Study

The stability of different types of platinum surfaces in the presence of chloride was evaluated by applying a potential of 1.2 V vs reversible hydrogen electrode while the associated mass change in the Pt electrode was monitored with an electrochemical quartz crystal microbalance. The platinum metal surfaces based on the particles and films show a large difference toward dissolution when exposed to small amounts of chloride. While an electrodeposited platinum metal film showed no degradation in a sulfuric acid solution containing 10 ppm of chloride, an electrode made from a fuel cell catalyst (50 wt % Pt/C) lost 10% of its platinum content over a 24 h period when exposed to a sulfuric acid solution containing 10 ppm of chloride. At a chloride concentration of 20 ppm, the onset potential of the Pt oxide formation increased compared to an electrode in a chloride-free solution. The degradation of nanoparticles thus appears to be much more significant than for the electrodeposited platinum electrodes.

Effect of Coating by Perfluorosulfonated Ionomer Film on Electrochemical Behaviors of Pt(111) Electrode in Acidic Solutions

Abstract Electrochemical behaviors of bare and perfluorosulfonated ionomer (PFSI) film-coated Pt(111) electrodes in perchloric and sulfuric acid solutions were investigated. While current peaks corresponding to specific adsorption and desorption of anions were clearly observed at the bare electrode, no such peaks were observed at the PFSI-coated electrode, showing that anions do not reach the electrode surface because of the cation-selective nature and/or adsorption of PFSI film. Although no structural change was observed by repetitive potential cycling as far as positive potential limit was more negative than that of oxide formation, significant structural change was noticed during potential cycling if the anodic potential limit was made more positive than oxide formation potential.

Combinatorial electrochemistry on Al–Fe alloys

Combinatorial material development was combined with high throughput microelectrochemistry to allow an efficient but comprehensive investigation of the interface chemistry of Al rich Al–Fe alloys as a function of their chemical composition. Composition spread thin films with a linear composition gradient were produced by thermal codeposition. A scanning droplet cell was used to determine the open circuit potential and to perform successive anodic oxide formation with intermittent impedance spectroscopy. The film formation factor, the relative permittivity of the oxides and the onset potential of oxide formation were determined quantitatively as function of the composition with a resolution of 0.5 at.%. An unexpected synergistic effect is found in a very narrow composition range between 9 and 12 at.% Fe. This effect, which shifts the onset potential by nearly 1 V, is discussed in terms of a local accumulation of Fe resulting in a redox stabilisation of space charge layer formation during high-field oxide growth. The results are supported by composition and depth dependent XPS measurements.

Volatile organic compounds at a rural site in western Senegal

The objectives of this study were to identify species and levels of volatile organic compounds (VOCs), and determine their oxidation capacity in the rural atmosphere of western Senegal. A field study was conducted to obtain air samples during September 14 and September 15, 2006 for analyses of VOCs. Methanol, acetone, and acetaldehyde were the most abundant detected chemical species and their maximum mixing ratios reached 6 parts per billion on a volume basis (ppbv). Local emission sources such as firewood and charcoal burning strongly influenced VOC concentrations. The VOC concentrations exhibited little temporal variations due to the low reactivity with hydroxyl radicals, with reactivity values ranging from 0.001 to 2.6 s−1. The conditions in this rural site were rather clean. Low ambient NO x levels limited ozone production. Nitrogen oxide (NO x ) levels reached values less than 2 ppbv and maximum VOC/NO x ratios reached 60 ppbvC/ppbv, with an overall average of 2.4 ± 4.5 ppbvC/ppbv. This indicates that the rural western Senegal region is NO x limited in terms of oxidant formation potential. Therefore, during the study period photochemical ozone production became limited due to low ambient NO x levels. The estimated ozone formation reactivity for VOCs was low and ranged between −5.5 mol of ozone/mol of benzaldehyde to 0.6 mol/mol of anthropogenic dienes.

Life cycle assessment of printing and writing paper produced in Portugal

The environmental sustainability is one of the current priorities of the Portuguese pulp and paper industry. Life Cycle Assessment (LCA) was the methodology chosen to evaluate the sustainability of the printing and writing paper production activity. This paper grade represents about 60% of the total production of paper in Portugal and its production is expected to increase in the near future. The main goal of this study was to assess the potential environmental impacts associated with the entire life cycle of the printing and writing paper produced in Portugal from Eucalyptus globulus pulp and consumed in Germany, in order to identify the processes with the largest environmental impacts. Another goal of this study was to evaluate the effect on the potential environmental impacts of changing the market where the Portuguese printing and writing paper is consumed: German market vs. Portuguese market. The main stages considered in this study were: forestry, pulp production, paper production, paper distribution, and paper final disposal. Transports and production of chemicals, fuels and energy in the grid were also included in these stages. Whenever possible and feasible, average or typical data from industry were collected. The remaining data were obtained from the literature and specialised databases. A quantitative impact assessment was performed for five impact categories: global warming over 100 years, acidification, eutrophication, non-renewable resource depletion and photochemical oxidant formation. In the German market scenario, the paper production stage was a remarkable hot spot for air emissions (non-renewable CO2, NOx and SO2) and for non-renewable energy consumption, and, consequently, for the impact categories that consider these parameters: global warming, acidification and non-renewable resource depletion. These important environmental impacts are due to the energy requirements in the printing and writing paper production process, which are fulfilled by on-site fuel oil burning and consumption of electricity from the national grid, which is mostly based on the use of fossil fuels. The pulp production stage was identified as the largest contributor to water emissions (COD and AOX) and to eutrophication. Considering that energy consumed by the pulp production processes comes from renewable fuels, this stage was also the most contributing to renewable energy consumption. The paper distribution stage showed an important contribution to NOx emissions, which, however, did not result in a major contribution to acidification or eutrophication. The final disposal stage was the main contributor to the photochemical oxidant formation potential due to CH4 emissions from wastepaper landfilling. On the other hand, paper consumption in Portugal was environmentally more favourable than in Germany for the parameters/impact categories where the paper distribution stage has a significant contribution (non-renewable CO2, NOx, non-renewable energy consumption, acidification, eutrophication and non-renewable resource depletion) due to shorter distances needed to deliver paper to the consumers. For the remaining parameters/impact categories, the increase observed in the final disposal stage in the Portuguese market was preponderant, and resulted from the existence of significant differences in the final disposal alternatives in the analysed markets (recycling dominates in Germany, whereas landfilling dominates in Portugal). The pulp and paper production stages were found to be of significance for almost all of the inventory parameters as well as for the impact assessment categories. The paper distribution and the final disposal stages were only of importance for some of the inventory parameters and some of the impact categories. The forestry stage played a minor role in the environmental impacts generated during the paper life cycle. The consumption of paper in Portugal led to a decrease in the environmental burdens of the paper distribution stage, but to an increase in the environmental burdens of the final disposal stage, when compared with the consumption of paper in Germany. This study provides useful information that can assist the pulp and paper industry in the planning of future investments leading to an increase in its sustainability. The results of inventory analysis and impact assessment show the processes that play an important role in each impact category, which allow the industry to improve its environmental performance, making changes not only in the production process itself, but also in the treatment of flue gases and liquid effluents. Besides that concern regarding pollution prevention, other issues with relevance to the context of sustainability, such as the energy consumption, can also be dealt with.

Nitrous oxide formation potential of various humid tropic soils of Malaysia: A laboratory study

Nitrous oxide (N2O) is formed mainly during nitrification and denitrification. Inherent soil properties strongly influence the magnitude of N2O formation and vary with soil types. A laboratory study was carried out using eight humid tropic soils of Malaysia to monitor NH4+ and NO3− dynamics and N2O production. The soils were treated with NH4NO3 (100 mg N kg−1 soil) and incubated for 40 days at 60% water-filled pore space. The NH4+ accumulation was predominant in the acid soils studied and NO3− accumulation/disappearance was either small or stable. However, the Munchong soil depicted the highest peak (238 μg N2O-N kg−1 soil d−1) at the beginning of the incubation, probably through a physical release. While the Tavy soil showed some NO3− accumulation at the end of the study with a maximum N2O flux of 206 μg N2O-N kg−1 soil d−1, both belong to Oxisols. The other six soils, viz. Rengam, Selangor, Briah, Bungor, Serdang and Malacca series, formed smaller but maximum peaks in an decreasing order of 116 to 36 μg N2O-N kg−1 soil d−1. Liming the Oxisols and Ultisols raised the soil pH, resulting in NO3− accumulation and N2O production to some extent. As such the highest N2O flux of 130.2 and 77.4 μg N2O-N kg−1 soil d−1 was detected from the Bungor and Malacca soils, respectively. The Selangor soil, belonging to Inceptisol, did not respond to lime treatment. The respective total N2O formations were 3.63, 1.92 and 1.69 mg N2O-N kg−1 soil from the Bungor, Malacca and Selangor soils, showing an increase by 49 and 99% over the former two non-limed soils. Under non-limed conditions, the indigenous soil properties, viz. Ca++ content, %clay, %sand and pH of the soils collectively could have influenced the total N2O formation.

Single crystal experiments on grains of polycrystalline materials: oxide formation on Zr and Ta.

Passivation on polycrystalline Zr (hcp) and Ta (bcc) depends on the crystallographic orientation of the individual grains, determined by electron back scattering diffraction (EBSD). Microelectrochemical experiments yield characteristic data, such as oxide formation potentials, formation factors, capacities, and thicknesses, of local oxide formation on single grains. Strong differences occur on Zr, for Ta only a small influence of crystallographic orientation is observed. The rate of oxide formation, determined from potentiodynamic and capacitive measurements, and EBSD pattern quality, increases with decreasing surface atom density. The dominating influence can be described by the Euler angle phi, the second angle phi2 has a smaller influence. The differences in surface atom density lead to a specific current-dependent potential drop during oxide growth and therefore to a shift in the oxide formation potential. Furthermore the crystallinity and epitaxy of the oxides can depend on the orientation of the base metal causing a variation in ion conductivity.

The potentials of mixed electrodes of corrodible metal and metal oxide

The electrode potential of oxide-covered metals and the mixed electrode potential of corrodible metals contacting with metal oxides are discussed in view of ionic and electronic transfer processes across the electrode interfaces. The oxide-covered metal electrode stands either at the potential of metal oxide formation or at the flat band potential of metal oxide. The mixed electrode of a corrodible metal and a metal oxide shifts its metallic corrosion potential toward the flat band potential of the oxide in the cathodic direction if the oxide is of the n-type, or in the anodic direction if the oxide is of the p-type. Photoexcitation of contacting oxides makes it possible for the anodic oxygen evolution to occur on the n-type oxides and for the cathodic hydrogen evolution to occur on the p-type oxides. It is suggested that the corrosion probability of metals reduces with the n-type oxides, whereas it increases with the p-type oxides.

Isoforms of cytochrome P450 on organic nitrate-derived nitric oxide release in human heart vessels

Glutathione S-transferases and the cytochrome P450 system have been proposed for the vascular biotransformation systems in the metabolic activation of organic nitrates. The present study was designed to elucidate the role of human cytochrome P450 isoforms on nitric oxide formation from organic nitrates using lymphoblast microsomes transfected with human CYP isoforms cDNA. CYP3A4-transfected microsomes had the most effective potential of nitric oxide formation from isosorbide dinitrate. Anti-CYP3A2 antibody (which cross-reacts with CYP3A4) or ketoconazole (an inhibitor of the CYP3A superfamily) inhibited nitric oxide formation from isosorbide dinitrate in rat heart microsomes. Immunohistochemistry of human heart also showed intense bindings of CYP3A4 antibody in the endothelium of the endocardium and coronary vessels. These results suggest that the CYP3A4-NADPH-cytochrome P450 reductase system specifically participates in nitric oxide formation from isosorbide dinitrate.

A simplified set-up for electrochemical mass spectrometry and the use of a gold substrate for the investigation of porous electrode materials

A cell for use in electrochemical mass spectrometry (EMS) using silicon rubber membranes and a gold substrate is described. The silicon rubber membrane used has a time constant and sensitivity for small molecules comparable with that of the microporous PTFE membranes used traditionally, but eliminates the need for a special prevacuum chamber and extra turbomolecular pump in the mass spectrometer. To investigate porous electrode materials a microporous electronically conducting film is formed on the silicon rubber membrane by evaporation. Below the potential of oxide formation the gold film behaves as an electrochemically inert substrate for the oxidation of methanol on different porous electrode materials. The applicability of the set-up has been demonstrated by mass spectrometric cyclic voltammetry (MSCV) on the oxidation of methanol on platinum black.

The use of on-line electrochemical mass spectrometry in the investigation of electrode- and electrolyte materials to be used in solid state fuel cells

A cell for use in electrochemical mass spectrometry (EMS) is described, which can be used for the investigations of either solid-liquid or solid-solid interfaces. A microporous electronically conducting gold film is formed on a commercial silicone rubber membrane by evaporation. Below the potential of oxide formation, the gold film behaves as an electrochemically inert substrate for the oxidation of methanol on different electrocatalysts. The silicone rubber membrane used has a time constant for small molecules comparable to that of the microporous PTFE membranes used traditionally, but eliminates the need for a special prevacuum chamber in the mass spectrometer. The setup has been used to measure data for the electrochemical oxidation of methanol on platinum black, and results comparable to those reported in the literature have been found. The setup has also been used to measure the release of ammonia from ammonium-zeolite-13X by monitoring the intensity of mass 15.01, where there is no interference from either water or oxygen. Release of ammonia was detected when current was passed through a sample of ammonium-13X, confirming that the compound is an ammonium ion conductor. Finally permeation of methanol through membranes of Nafion, tin-mordenite and pillared α-ZrP from a 50% mixture of methanol and water has been measured. The permeation of methanol through Nafion was found to be an order of magnitude higher than the permeation through the two inorganic proton conductors of which the tin-mordenite showed the lowest permeability.

Electrochemical and Structural Behaviour of Pd+ Implanted TiO2‐Films in Dependence on the Pd+‐Concentration

AbstractAccording to our recent investigations, ion implantation into oxide films yields an increase in capacity, an enhancement of ETR and a decrease in the band gap. These effects are now measured in dependence on the implanted Pd+‐concentration. Due to doping or metallization by Pd as well as to radiation damage and amorphization, the implantation effects increase up to 1 to 3% Pd+ but then saturation is observed. Saturation of amorphization is due to fast annihilation of the Frenkel defects during implantation, but saturation of doping by Pd may be caused by the Pd‐cluster formation. The defect states of the oxide films can be annihilated during the andic polarization (repassivation). – The interface Ti/TiO2 is mixed by the implanted Pd+‐ions. The surface structure and grain boundaries of the oxide films disappear during Pd+‐implantation. This can be seen with Scanning Electron Microscopy and measured by localized photocurrent and Transmission Electron Microscopy. The implanted films are reconstructed by repassivation, and an additional oxide is grown at the interfaces of the oxide. The latter can be concluded from Rutherford Backscattering Spectroscopy (RBS). The Pd‐enrichment at the surface, at intermediate repassivation potentials, is measured by X‐ray Photoelectron Spectroscopy (XPS) and it can be correlated exactly with the results of ETR experiments. XPS ad RBS show that all implanted Pd+ disappears during repassivation up to the oxide formation potential.