Electrolytic Oxygen Research Articles

In-situ electrolytic oxygen is a feasible replacement for conventional aeration during aerobic composting

Aerobic composting is an effective recycling method for the disposal and resource utilization of organic solid waste. However, the inappropriate aeration mode used during conventional aerobic composting (CAC) often results in low oxygen utilization efficiency and loss of temperature, which further leads to a long maturation period and large odorous gas (NH3) pollution. Herein, a novel electrolytic oxygen aerobic composting (EOAC) process was invented first using in-situ oxygen generation for aeration by the electrolysis of water in compost. Our results demonstrated that the germination index (GI) significantly increased during EOAC, and the maturation time of compost was shortened by nearly 50% during EOAC compared to CAC, indicating higher oxygen utilization efficiency during EOAC. Meanwhile, NH3 emissions, N2O emissions, and nitrogen loss during the EOAC process decreased by 61%, 46%, and 21%, respectively, compared to CAC. The total relative abundance of thermophilic and electroactive bacteria during EOAC increased remarkably. EOAC inhibited ammoniation, nitrification, and denitrification, and weakened N-associated functional genes. A techno-economic analysis indicated that EOAC had greater technical superiority and cost advantages compared to CAC. This study represents proof-of-principle for EOAC and suggests that in-situ electrolytic oxygen is a feasible replacement for conventional aeration during aerobic composting.

Electrolysers for producing net-zero heat

In addition to fuel cell applications, water electrolysis affords several opportunities for producing high-grade heat by utilising electrolytic hydrogen and oxygen in combustion applications. This can reduce or eliminate the atmospheric emissions associated with the combustion of conventional fuels. Importantly, net-zero heat can be produced if the electrolyser is powered by renewable electricity, whereby the output gases may be termed green hydrogen and green oxygen. This paper provides an overview of prospective applications for electrolysers in the heat sector by considering three general implementation pathways based on how the electrolytic oxygen is used.

Green hydrogen: The only oxygen and water balanced fuel

The use of any fuel depletes the oxygen content of the atmosphere, with one exception: hydrogen produced from water. Water electrolysis liberates oxygen from water in the precise stoichiometric ratio required to oxidise (and hence release energy from) the co-produced hydrogen. As a commercial fuel production process, electrolysis is unique in providing the oxidant as well as the fuel; electrolytic oxygen can thereby replenish the consumption of atmospheric oxygen due to hydrogen use. Furthermore, the amount of water consumed during electrolysis is reproduced when the hydrogen is oxidised. So the use of electrolysers and electrolytic hydrogen does not affect global oxygen and water resources: ‘green’ hydrogen may thus be described as the only oxygen and water balanced fuel. Conversely, the use of hydrogen derived from fossil fuels (with or without carbon capture and storage, CCS) depletes the oxygen resource and increases water vapour emissions to the atmosphere, which enhances the rate of global warming. Therefore, a worldwide multi-TW deployment of electrolysers could provide very substantial amounts of hydrogen for the energy system, and oxygen for the global ecosystem. This should be done in combination with other measures for combatting oxygen depletion (such as reducing combustion, increasing forestation, and reducing nutrient inputs to the ocean from sewage and agriculture). In this way the long-term objective should be to stabilise, or even increase slightly, the concentrations of atmospheric and aquatic oxygen, and possibly speed up the decay of atmospheric methane. Clearly the production-and-use of hydrogen derived from fossil fuels contravenes this objective, and should cease without delay.

UKF-Based State Estimation for Electrolytic Oxygen Generation System of Space Station

Electrolytic oxygen generation system (EOGS) is the only system that can provide oxygen for astronauts in a physicochemical regenerative way in a long-term manned spacecraft. In order to ensure that the astronauts in the cabin can obtain a continuous and enough oxygen supply, it is necessary to carry out real-time condition monitoring and fault diagnosis of the EOGS. This paper deals with condition monitoring and fault diagnosis of the EOGS. Firstly, the dynamic model of the system is established based on the principle electrolysis for actual oxygen production system and the state observer of the system has been designed by using unscented Kalman filter (UKF). The total pressure in the cabin and the partial pressure of oxygen in the electrolytic cell can be observed. Then, considered the actual conditions of the manned space mission with one more astronaut, i.e., 3 astronauts, the simulation experiment is carried out. The simulation results show that the method can effectively estimate the system state, and it is of great significance to ensure the normal operation of the electrolytic EOGS system in the space station.

Non-stoichiometric NiOx nanocrystals for highly efficient electrocatalytic oxygen evolution reaction

Abstract Designing a low–cost, large–scale and highly–active electrolytic oxygen evolution catalyst is still a huge challenge. Pure stoichiometric NiO is inevitably an insulator, which hampers the electron transfer and transport in catalysis. While non-stoichiometric NiOx is a wide bandgap p-type semiconductor. The conductive interface of non-stoichiometric NiOx NCs is successfully fabricated, which the p-type conductivity of NiOx originates from two positive charge compensation which favored Ni2+ vacancies. The valence band (VB) of NiOx is well adjustable so that the strong electron interaction induces electronic structure modulation, which optimizes the binding energy of *OOH intermediates. In the alkaline water splitting, non-stoichiometric NiOx NCs exhibit remarkable performance toward OER with an overpotential of 330 mV (1.56 V vs. RHE) at 10 mA cm−2 and a Tafel slope of 105.17 mV dec−1, as well as an extraordinary robust stability. Detailed investigations show that the high density of defects combine with oxygen atoms to form NiOOH species, which are conducive to the OER kinetics. This work offers valuable generalized insights for constructing robust non-stoichiometric metal oxides electrocatalysts and encouraging for large-scale practical applications.

Methanol synthesis through CO2 capture and hydrogenation: Thermal integration, energy performance and techno-economic assessment

This work assesses the opportunity of using “green” methanol (MeOH) produced from renewable electricity as a vector for the decarbonization of chemical process industry. We developed a comprehensive process model to simulate all the relevant sections for the conversion of 1.25 t/h of captured CO2 from a coal-fired power plant to methanol, using “green” hydrogen via water electrolysis. We applied the pinch analysis methodology for an improved thermal management of the integrated carbon capture, electrolysis and methanol synthesis plant. A network of recovery heat exchangers was designed with the pinch analysis methodology, allowing a thermal energy saving of 4.59 MW, with a net reduction of heating and cooling demands by 81 % and 47 %, respectively, and an improvement of the global efficiency of the plant from 26.74 % to 37.22. We followed a bottom-up approach for the techno-economic assessment, defining a confidence range for the main indicators of system economic viability. We assessed their sensitivity to the cost of electricity from seven renewable energy sources and to the option of selling oxygen produced by water electrolysis, in three different cost scenarios (1-optimistic, 2-realistic, 3-pessimistic). The estimated values of the cost of methanol (COM) span from a maximum range of 2624–2706 €/t (in the case of concentrated solar power) to a minimum of 565–647 €/t (hydropower with highest valorization of electrolytic oxygen), hence resulting in line with the future trends of methanol market price (400–800 €/t) in five of the considered configurations. We have finally estimated the levelized cost of methanol (LCOM) ensuring an internal rate of return ranging from 0 to 10 % for each of the techno-economic scenarios identified. Assuming 10 % as the target, LCOM in case of hydropower as renewable energy source spans from 874 to 1356 €/t, hence close to the future market price of MeOH with margin of improvement (655–1135 €/t) in case of lower costs of electric energy.

Functions of MnOx in NaCl Aqueous Solution for Artificial Photosynthesis.

SummaryPhotoelectrochemical water splitting has been intensively investigated as artificial photosynthesis technology to convert solar energy into chemical energy. The use of seawater and salted water has advantages for minimum environmental burden; however, the oxidation of Cl− ion to hypochlorous acid (HClO), which has toxicity and heavy corrosiveness, should occur at the anode, along with the oxygen evolution. Here, O2 and HClO production in aqueous solution containing Cl− on photoanodes modified with various metal oxides was investigated. The modification of MnOx resulted in the promotion of the O2 evolution reaction (OER) specifically without HClO production over a wide range of conditions. The results will contribute not only to the practical application of artificial photosynthesis using salted water but also to the elucidation of substantial function of manganese as the element for OER center in natural photosynthesis.

Comparison of different system layouts to generate a substitute of natural gas from biomass and electrolytic hydrogen

The production of electrolytic hydrogen is considered among the best solution to mitigate the grid instability problems which arise from the widespread distribution of renewable energy sources, such as wind and solar. However, hydrogen is not easy to stock and distribute. Possible solutions are represented by its direct injection into the existing pipeline for natural gas distribution or its utilisation for the production of a substitute of natural gas. In this last case, which follows the so called approach of “power to gas”, a source of carbon is required. Preferably the carbon should come from biomass, since it can be considered “renewable carbon”.Starting from this idea, this study analyses two different approaches, depending on the grid power demand. In a first layout, biomass is gasified with electrolytic hydrogen to generate directly a methane rich syngas. After water condensation, the syngas is fed to a methanation process to convert almost completely carbon in methane.In the second layouts the biomass is gasified with electrolytic oxygen and the syngas is fed, together with other electrolytic oxygen, to a power unit, such as an internal combustion engine, a gas turbine or a high temperature fuel cells (SOFC). The exhaust gas from these power units is composed almost exclusively by carbon dioxide and water vapour. After water condensation, the carbon dioxide is fed together electrolytic hydrogen to a methanation process to obtain the substitute of natural gas.An overall best efficiency of roughly 74% is obtained when the plant is not connected to the grid. On the contrary, when electricity can be absorbed by the grid, best efficiency of 59.4% is reached utilising, as power unit, a SOFC fed at 6 bars.In all cases the input is low value energy (biomass and unstable electric power) and the output is high value energy constituted by a substitute of natural gas and stable electric power.

Enhanced electrolytic oxygen evolution by the synergistic effects of trimetallic FeCoNi boride oxides immobilized on polypyrrole/reduced graphene oxide

Trimetallic FeCoNiBOx/PPy/rGO nanocomposites exhibit optimal OER activity due to the synergistic effects of each component.

STORING RENEWABLE ENERGIES IN A SUBSTITUTE OF NATURAL GAS

This paper proposes a way to obtain valuable electric power and valuable fuel starting from renewable variable electric power plus biomass and/or waste products. Biomass/biofuel can be oxyburned using electrolytic oxygen to generate electric power. Gas turbines or internal combustion engines are suitable to such a task, but there is the problem of very high temperatures connected to oxy combustion. In the case of gas turbine the inlet temperature could be controlled by adding steam and/or carbon dioxide, while in the case of internal combustion engines only carbon dioxide could be used. In such a way the exhaust gas continues to be formed by carbon dioxide and steam which can be easily separated by condensation. Carbon dioxide is fed to a Sabatier process together with electrolytic hydrogen to generate a gas with characteristics similar to natural gas. Although electrolytic hydrogen could be used directly both in internal combustion engines and fuel cells, significant problems to hydrogen distribution and on-board storing still exists. Therefore the substitute of natural gas could be a real bridge solution for the short/medium term. A simulation has been carried out and the resulting efficiencies range from 0.52 to 0.58.

High-performance electrolytic oxygen evolution with a seamless armor core-shell FeCoNi oxynitride.

Highly active, low-cost, and durable electrocatalysts for the water oxidation reaction are pivotal in energy conversion and storage schemes. Here we report a nitride-core, oxide-shell-armor structured FeCoNi oxynitride as an efficient oxygen evolution electrocatalyst with a homogeneous nitride (Fe0.70Co0.56Ni0.92N1.0O0.06) core and an oxide (Fe0.48Co0.1Ni0.21N0.05O1.0) shell. The catalyst demonstrated excellent activity for the oxygen evolution reaction with a current density of 10 mA cm-2 at a low overpotential of 0.291 V in alkaline media (1 M KOH), which is superior to the activities of commercial IrO2, RuO2, and Pt/C catalysts and comparable to those of state-of-the-art catalysts (e.g., NiFe-LDH, NiCo2O4, O-NiCoFe-LDH). Density functional theory simulations suggested that the incorporation of multiple metal elements can indeed improve the reaction energetics with a synergistic effect from the core-shell structure. This unique structure of a nitride-core with a oxide-shell presents a new form of multimetallic oxynitride with compelling performance in electrolytic oxygen evolution.

MHD effect under the interaction of external magnetic field with electrolytic hydrogen and oxygen bubbles

MHD effect under the interaction of external magnetic field with electrolytic hydrogen and oxygen bubbles

Environmental impact of the excess electricity conversion into methanol

Abstract In this work, the impact on the environment of a renewable methanol production in combination with a wastewater treatment plant (WWTP) was analysed. Carbon dioxide from biogas and hydrogen from water electrolysis were used as resources for methanol synthesis. Additionally, it was decided to use the available excess of electricity and it was prepared for a small city in North-West of Germany (Emden) to have a realistic scenario. As a consequence, methanol plant was simulated with the use of ASPEN Plus software in order to calculate the mass balance and energy requirement. Subsequently a comparative life cycle assessment (cradle-to-gate) was conducted in order to compare renewable methanol with conventional process and also with methanol produced from biomass. In order to evaluate possible impact on the environment, 11 common impact categories were selected. Results showed that enough excess electricity was already available to utilize the whole CO2 from WWTP in Emden. Subsequently it was found that the production of renewable methanol, without emissions related to windmill construction, has much lower impact on the environment than conventional production according to all impact categories. Furthermore, the combination of power-to-methanol plant with WWTP allowed utilization of the biogenic carbon dioxide and application of the produced via electrolysis oxygen. Therefore, thanks to substitution of air with produced oxygen, a reduction in electricity consumption for the aeration system could be possible. However, taking into account the emissions related to wind electricity, renewable methanol would cause lower emissions according to 5 impact categories (acidification potential, climate change, ozone layer depletion, photochemical oxidation, and primary energy demand from non-renewable resources) than natural gas or biomass based methanol.

Cogeneration of power and substitute of natural gas using electrolytic hydrogen, biomass and high temperature fuel cells

Energy storage from renewable sources is one of the main current goals for the energy sector, and the production of a substitute of natural gas could be a good solution to solve the problem in the short term, helping the transition to hydrogen in the long term.Renewable energy sources usually generate variable electric power or medium/low energy content gas. This paper proposes a way to upgrade these products through the use of electrolytic hydrogen. By using electrolytic oxygen as an oxidant for biomass partial oxidation and for high temperature fuel cells, the exhaust gas after post-combustion is an almost pure mixture of water and carbon dioxide. Once such a gas is dehydrated, the carbon dioxide can be mixed with electrolytic hydrogen to obtain methane through the Sabatier process.Four layouts based on molten carbonate fuel cells and solid oxide fuel cells has been investigated. The results obtained are very similar: the conversion efficiency is close to 60% and the mix of energy output consist of fuel for about 75% and electric power for about 25%.

High‐Performance Electrolytic Oxygen Evolution in Neutral Media Catalyzed by a Cobalt Phosphate Nanoarray

AbstractThe topotactic conversion of cobalt phosphide nanoarray on Ti mesh into a cobalt phosphate nanoarray (Co‐Pi NA) via oxidative polarization in phosphate‐buffered water is presented. As a 3D oxygen evolution reaction (OER) catalyst electrode at neutral pH, the resulting Co‐Pi NA/Ti shows exceptionally high catalytic activity and demands an overpotential of only 450 mV to drive a geometrical catalytic current density of 10 mA cm−2. Notably, this catalyst also shows superior long‐term electrochemical stability. The excellent catalytic activity can be attributed to that such 3D nanoarray configuration allows for the exposure of more active sites and the easier diffusion of electrolytes and oxygen.

High‐Performance Electrolytic Oxygen Evolution in Neutral Media Catalyzed by a Cobalt Phosphate Nanoarray

The topotactic conversion of cobalt phosphide nanoarray on Ti mesh into a cobalt phosphate nanoarray (Co-Pi NA) via oxidative polarization in phosphate-buffered water is presented. As a 3D oxygen evolution reaction (OER) catalyst electrode at neutral pH, the resulting Co-Pi NA/Ti shows exceptionally high catalytic activity and demands an overpotential of only 450 mV to drive a geometrical catalytic current density of 10 mA cm-2 . Notably, this catalyst also shows superior long-term electrochemical stability. The excellent catalytic activity can be attributed to that such 3D nanoarray configuration allows for the exposure of more active sites and the easier diffusion of electrolytes and oxygen.

Suppression of Oxide Growth on Ti Substrate of Ir1-XSnxO2/Ti Anodes in Electrolytic Oxygen Evolution

INTRODUCTION In order to prevent global warming and to supply renewable energy in the form of methane, Hashimoto et al. have been proposing global CO2 recycling and have tailored the necessary key materials, that is, the anodes and cathodes for seawater electrolysis and catalysts for CO2 methanation by the reaction with hydrogen. The most difficult was the anode for seawater electrolysis, because the anode should evolve only oxygen without forming chlorine even in seawater electrolysis. Titanium is generally used as the electroconductive substrate. We usually covered the titanium substrate with IrO2 for prevention of oxidation of titanium. In chloride containing electrolytes, chlorine evolution occurs preferentially on the IrO2-covered titanium. Thus, we needed to prepare g-MnO2-type electrocatalysts covering the IrO2 layer for exclusive oxygen evolution in seawater electrolysis. We revealed that the Ir1-xSnxO2 double oxides have better protectiveness against oxidation of titanium than IrO2. The Mn1-x-yMoxSnyO2+x/Ir1-xSnxO2/Ti anode showed more than 99.9% oxygen evolution efficiency for 4200 h in the electrolysis of 0.5 M NaCl solution of pH 1 at 1000 Am-2. Although the oxygen evolution efficiency was close to 100%, the oxide growth on the titanium substrate was unavoidable due to the inward diffusion of oxygen through electrocatalyst and intermediate layers during oxygen evolution. The present work aimed to improve the protectiveness of Ir1-xSnxO2 double oxide. Since the Ir1-xSnxO2/Ti anodes themselves are oxygen evolution anodes in chloride free aqueous solutions, the protectiveness of Ir1-xSnxO2 double oxide during oxygen evolution at high current densities was examined using the Ir1-xSnxO2/Ti anodes in H2SO4 solutions. EXPERIMENTAL After surface roughening by immersion in 11.5 M H2SO4 the titanium substrate was coated with butanol solutions of H2IrCl6 and SnCl4, in which the sum of metallic cations was 0.1, 0.26 or 0.52 M. The specimens were dried at 80oC for 10 min and calcined at 250-450oC for 10 min. This procedure was repeated three times and the final calcination was continued for 0.5-24 h. The anodes were previously used for the electrolysis at 13,333 Am-2 in 3 M H2SO4 solution at room temperature for various periods of time, and then characterization of the used anodes was carried out by electrochemical measurements in 1 M H2SO4 solution at 25°C. Galvanostatic polarization curves were measured by the current density rise every 1 min. The potential rise due to the solution resistance at high current densities was corrected by the ordinary current interruption technique. Two more different current interruption techniques were applied at higher current densities using a digital oscilloscope for the measurement of the potential decays at every 0.0625 ms and 0.4 ms, respectively. RESULTS AND DISCUSSION The oxide growth on the titanium substrate occurred during electrolysis at high current densities for long periods. The oxide growth rate was estimated with anodic polarization curves and current interruption technique by the assumption of equivalent circuit of oxide covered metal electrode. When the sum of Ir4+ and Sn4+ was 0.52 M, the solely IrO2-coated anode showed the lowest rate of resistance growth. However, when the sum of Ir4+ and Sn4+ was 0.26 M, an increase in Ir4+ higher than 0.13 M was not effective to decrease the oxide growth. When the sum of Ir4+ and Sn4+ was 0.1 M, the minimum oxide growth rate appeared at 0.04 M Ir4+, where the oxide growth rate was similar to that of the anode prepared in 0.13 M Ir4+ - 0.13 M Sn4+ solution. Consequently, in order to save iridium, lower concentrations of Ir4+ and Sn4+ will be useful. On the other hand, an increase in calcination temperature led to incorporation of oxidized titanium in Ir1-xSnxO2. This also led to a resistance increase. Furthermore, the increase in calcination temperature resulted in potential increase at low current densities. This implied a decrease in the oxygen evolution activity due to inclusion of Ti2+ in Ir1-xSnxO2. However, the formation of triple oxide of Ir1-x-ySnxTiyO2 was not always detrimental for the elongation of the life of the anode. The growth rate of titanium oxide during anodic polarization at 13,333 Am-2 in 3 M H2SO4 solution was lowest when the anode was formed by calcination at 450°C. Consequently, the protectiveness of Ir1-x-ySnxTiyO2 formed by calcination at 450°C was highest even if oxidized titanium was included in the active anode for oxygen evolution. Consequently, the optimum preparation condition of Ir1-xSnxO2/Ti anodes was coating of Ti substrate with butanol solution of 0.13 M Ir4+ and 0.13 M Sn4+ and calcination at 450°C for 1 hour.

Durability of Electrodeposited Ni-Fe-Co-C Anodes for Alkaline Water Electrolysis

IntroductionWe have been studying more than a quarter of century for supply of renewable energy in the form of methane via electrolytic hydrogen generation using carbon dioxide as the feedstock. Although we created cathodes and anodes for direct seawater electrolysis, the energy efficiency was not sufficient. For immediate industrialization, we are concentrating our current effort on alkaline water electrolysis, creating efficient cathodes and anodes. The present work aimed to determine the composition of active Ni-Fe-Co-C alloy anodes prepared by electrodeposition and to examine the durability for continuous electrolysis at a high current density of 6000 Am-2 in 4.5 M KOH at 90°C. Experimental Procedures The substrate for electrodeposition was a chemically etched Ni plate. Electrodeposition was carried out at a current density of 300 Am-2 for 10 min in 1.14 M NiSO4-0.189 M NiCl2-0.49 M H3BO3-0.104 mM CH3(CH2)11OSO3Na solutions containing various concentrations of FeSO4, CoSO4 and lysine, the pH of which was adjusted at 1.5 by the addition of 18 M H2SO4. Lysine was added as the carbon source. The composition of metallic elements in the electrodes was analyzed by electron probe microanalysis, and carbon was chemically analyzed by combustion infrared absorption method. The solution used for oxygen evolution was 4.5 M KOH at 90oC. The activity of the anodes was evaluated from galvanostatic polarization curves measured by the current density rise every 1 min. The potential rise due to the solution resistance at high current densities was corrected by the current interruption technique. Potentiodynamic polarization curves were also measured at a potential sweep rate of 0.52mV-1 for comparison. Results and Discussion As-deposited alloys were used for examination of oxygen evolution activity. Ni was a stable anode but less active for industrial electrolysis. The addition of Co ion and lysine to the deposition electrolyte containing Ni ion enhanced the oxygen evolution activity, but the activity of Ni-Co-C alloys was not yet sufficiently high. Ni-Fe-Co-C alloys deposited showed significantly high activity for oxygen evolution. An increase in Fe content in the alloy was more effective than the increase in Co content for enhancement of oxygen evolution activity. Thus, an increase in Co concentration in deposition electrolytes did not largely change the activity because the increase in Co content in the alloy resulted in the decrease in the content of Fe. The addition of lysine to the deposition electrolytes containing Ni, Fe and Co ions enhanced the oxygen evolution activity. The highest activity was attained at 0.2 M lysine in the deposition solution, but further increase in lysine concentration was not effective. An increase in lysine concentration led to asymptotic increase in the C content in the Ni-Fe-Co-C alloys up to about 6 at%. The deposition electrolyte to form the most active Ni-Fe-Co-C alloy for oxygen evolution was 1.33M Ni-0.072M Fe-0.018M Co-0.2M lysine solution. When the Ni-Fe-Co-C alloy prepared from this electrolyte was used for oxygen evolution at a current density of 6000 Am-2 for 800 h, the mass loss was about 5 % of the original mass. The galvanostatic polarization potential of as-deposited Ni-Fe-Co-C alloy measured by the current density rise every 1 min was in the active region at lower current densities, but the potential shifed to the oxygen evolution region at higher current densities. Once the specimen was polarized in the oxygen evolution region, the potential was stayed in the oxygen evolution region even when the current density was lowered. After oxygen evolution at 6000 Am-2 for long period of time, the potential stayed in the oxygen evolution region regardless of current densities. In fact, the dissolution current density estimated from the mass loss by polarization at 6000 Am-2 for 800 h even on the assumption of Fe dissolution in the form of Fe6+ as FeO4 2- was only 4.5 x 10-3 Am-2 that is less than one-millionth of oxygen evolution current. Consequently, the active Ni-Fe-Co-C alloy anode thus prepared is sufficiently stable maintaining the passive state in the severe environment for oxygen evolution at 6000 Am-2 in a concentrated KOH solution at 90°C for long period of time. Conclusion The active oxygen evolution anode in alkaline water electrolysis for hydrogen production was created. The addition of Fe, Co and C to Ni enhanced the oxygen evolution efficiency in 4.5 M KOH solution at 90°C. The Ni-Fe-Co-C alloy thus prepared kept the passive state during electrolytic oxygen evolution at 6000 Am-2 for a long period of time.

Storing renewable energies in a substitute of natural gas

This paper proposes a way to obtain valuable electric power and valuable fuel starting from renewable variable electric power plus biomass and/or waste products.Biomass/biofuel can be oxyburned using electrolytic oxygen to generate electric power. Gas turbines or internal combustion engines are suitable to such a task, but there is the problem of very high temperatures connected to oxycombustion. In the case of gas turbine the inlet temperature could be controlled by adding steam and/or carbon dioxide, while in the case of internal combustion engines only carbon dioxide could be used. In such a way the exhaust gas continues to be formed by carbon dioxide and steam which can be easily separated by condensation. Carbon dioxide is fed to a Sabatier process together with electrolytic hydrogen to generate a gas with characteristics similar to natural gas.Although electrolytic hydrogen could be used directly both in internal combustion engines and fuel cells, significant problems to hydrogen distribution and on-board storing still exists. Therefore the substitute of natural gas could be a real bridge solution for the short/medium term. A simulation has been carried out and the resulting efficiencies range from 0.52 to 0.58.

Continuous treatments of synthetic groundwater by an in situ denitrification and oxidation process with injection of electrolytic hydrogen and oxygen

Long-term continuous treatments of synthetic groundwater containing 15.06 ± 0.55 mg-N/L nitrate were conducted using an in situ denitrification and oxidation process under different operating conditions. In the experiments, electrolytic hydrogen and oxygen were injected upstream and downstream in a laboratory-scale aquifer, respectively, and measurements were made for nitrate, nitrite, pH, dissolved oxygen, dissolved hydrogen, total organic carbon (TOC), turbidity, and chromaticity. Experimental results demonstrated that steady-state denitrification and oxygenation of groundwater were achieved over 820 days. During the initial phase of the experiments, nitrite was accumulated at a level of several mg-N/L in a hydrogen-injected zone, but it was almost completely oxidized to nitrate in a downstream oxygen-injected zone. In subsequent experiments, nitrite accumulation was not observed in effluent, and satisfactory treatments were achieved. Effluent concentrations of total nitrate and nitrite, TOC, turbidity, and chromaticity were generally below World Health Organization guidelines for drinking water (11.3 mg-N/L). It should be mentioned that water quality parameters such as TOC, turbidity, and chromaticity were lower in effluent than influent, and no clogging problem was observed. From these results, we concluded that the present in situ process has superior properties in terms of long-term performance and stability.