O2 Stream Research Articles

Microwave-Driven Reduction Accelerates Oxygen Exchange in Perovskite Oxides.

Microwave-assisted oxide reduction has emerged as a promising method to electrify chemical looping processes for renewable hydrogen production. Moreover, these thermochemical cycles can be used for thermochemical air separation, electrifying the O2 generation by applying microwaves in the reduction step. This approach offers an alternative to conventional cryogenic air separation, producing pure streams of O2 and N2. The electrification by microwaves lowers the requirements for titanate perovskites (CaTi1-xMnxO3-δ), which typically demand high temperatures for thermochemical cycles. Microwave activation allows for a drastic reduction in the operation conditions of the reduction reaction, leading to unprecedentedly rapid absorption-desorption cycles (<3 min per cycle). For CaTi0.8Mn0.2O3-δ, we achieved a cycle-averaged O2 production of 2.6 mL g-1 min-1 at 800 °C, surpassing conventional values of materials operating in the high-temperature regime. This method could significantly impact thermochemical air separation by enabling a faster oxygen absorption-desorption cycle at more moderate temperatures than those of conventionally heated processes.

An Experimental Investigation into Ammonia Oxidation and NOx Emission in a Packed-Bed of Quartz Particles

ABSTRACT The effect of temperature, initial NH3 concentration, equivalence ratio, and flowrate on the characteristics of ammonia (NH3) oxidation and associated NOx formation in a fixed-bed reactor packed with quartz particles has been systematically investigated with a stream of NH3 and O2 in He over a range of furnace set temperatures (900 K – 1400 K), initial NH3 concentrations (2% – 10%), equivalence ratios (ɸ = 0.8, 0.9, 1.0, 1.1), and total flowrates (145 mL/min, 289 mL/min, and 434 mL/min). Benchmark flow reactor experiments, without the quartz particles in the reactor under otherwise similar conditions, were previously performed and served as a reference case for this work. Compared to the flow reactor results, the packed-bed data indicated a lower reaction onset temperature and more gradual NH3 conversion across the temperature range. Both packed-bed and flow reactor experiments indicated that decreasing flowrate, thus increasing residence time, resulted in greater NH3 conversion. NH3 conversion in the fixed-bed reactor was similar for all equivalence ratios at temperatures ≤1200 K, above which NH3 conversion increased with decreasing equivalence ratio, a trend broadly aligned with previous flow reactor experiments. For all conditions examined, NO was the major NOx component and NO2 was insignificant. Across the range of equivalence ratios, NO emission was low, yet noticeable, from 900 K – 1100 K, before spiking at 1200 K. Above 1200 K, NO emissions decreased before drastically increasing again at 1400 K under fuel-lean conditions. At temperatures ≤1300 K, NO was generally found to decrease with decreasing equivalence ratio, while at 1400 K, NO increased with decreasing equivalence ratio. NO emissions were significantly lower in the packed-bed compared to the flow reactor scenario at temperatures ≥1300 K.

Review: Uninterrupted Liquid Hydrogen (E-Methanol) Production framework to deliver Clean &amp; Green Energy

Potential broad impact: Integrating solar, wind, and conventional energy to feed the electrolyze after completion of the electrochemical process will produce two streams of O2 and H2. The hydrogen stream will be stored and provided with uninterrupted feed to a catalytic reactor in the presence of CO2. It will produce EMethanol[1]. However, this depends on these resources' reliability, cost, and availability, with the highest potential for expansion to the size needed for large-scale deployment to produce e-methanol[2]. This is known as electro-fuel, which provides electricity and fuel for electric and diesel vehicles[3][4]. As witnessed the versatility of Hydrogen in these applications highlights its significance in various industrial sectors. As the world looks towards sustainable and clean energy solutions, the role of Hydrogen is expected to grow even further [5]. However, the central part of Hydrogen is produced from fossil fuels (known as gray and brown Hydrogen) [6], and only a minimal amount of almost 4% is delivered through an electrolysis process using renewable energy to complete the chemical process [7], known as green Hydrogen. The transition to a more sustainable hydrogen economy involves scaling up the production of green Hydrogen through electrolysis and advancing technologies to improve efficiency and reduce costs associated with this process [8],[9]. Recently research indicated that production and consumption of the Green Hydrogen is the future of sustainable power delivery by replacing fossil fuel [10]. The fossil and Biomass also catalyzing the GHG (Green House Gases) with high carbon intensity, this is biggest challenge to deliver clean energy [11]. In the first instance, this research proposed an integrated Modular, which incorporate Renewable(photovoltaic) and Conventional Power sources to complete electrolysis process and its port equipment(s) to deliver uninterrupted clean Energy inform of Liquid Green Hydrogen for Electricity and to replace diesel [12]]13].

Self-sufficient metal-air battery systems enabled by solid-ion conductive interphases.

Metal-air batteries including Li-air, Na-air, Al-air, and Zn-air, have received significant scientific and technological interest for at least the last three decades. The interest stems primarily from the fact that the electrochemically active material (O2) in the cathode can in principle be harvested from the surroundings. In practice, however, parasitic reactions with reactive components other than oxygen in dry air passivate the anode, limit cycling stability of air-sensitive (e.g., Li, Na, Al) and electrolyte-sensitive (e.g., Zn) anodes, in most cases obviating the energy-density benefits of harvesting O2 from ambient air. As a compromise, so-called metal-oxygen batteries in which pure O2 is used as the active cathode material have been extensively studied but are understood to be of little practical relevance because of the large infrastructure required to produce the pure O2 stream. Here, we report on the design of solid-ion conductive chemically inert metal interphases that simultaneously protect a metal anode from parasitic reactions with electrolyte components and which facilitate rapid interfacial ion transport. Interphases composed of indium (In) are reported to be of particular interest for protecting Li and Na anodes from passivation in air whereas interphases composed of Sn are shown to prevent chemical and electrochemical corrosion of Zn anodes in alkaline electrolytes. We report further that these protections enable so-called self-sufficient metal-air batteries capable of extended cycling stability in ambient air environments.

Integration of a Microchannel Reactor in a CECE Process for H2 Removal from the O2 Stream Produced by the H2 Generator

A hydrogen generator is used in the combined electrolysis catalytic exchange process (CECE) for low-level tritiated water detritiation as a source of H2 (Q2) for the liquid-phase catalytic exchange column(s) within the process. To produce H2, the H2 generator employs an electrolytic process for H2O splitting into H2 and O2, resulting two streams: a hydrogen stream and an oxygen stream. During the detritiation of water, tritium is accumulated in the H2 generator in the form of tritiated water, and the effluent streams (hydrogen and oxygen) show in time an increased tritium concentration in the form of both tritiated water vapors and gas, which need to be recovered. The traditional methods for recovery present a risk of explosion due to the high concentration of hydrogen in oxygen (above 3%, while the explosion limit is 1%). In order to minimize this risk, a microchannel reactor with platinated channels has been developed and tested for the oxidation of tritiated hydrogen from the O2 electrolyzer stream in view of its recovery in a scrubber column and returned as tritiated water to the process. The reactor has been coupled to an electrolyzer and tested with regard to the operating temperature. It has been found that it reaches the highest oxidation efficiency of hydrogen when operated at 200°C. The design of the equipment is presented together with the results of the tests done with the equipment integrated in the CECE process.

Sputtering Pt on Low-Loading Iridium-Based Anode to Improve Both Cell Performance and Gas Permeation Issue in PEM Water Electrolysis

Polymer electrolyte membrane (PEM) water electrolysis is one of the most promising technologies which can integrate with renewable sources to produce sustainable hydrogen energy. Thin membranes were preferred for making membrane electrode assembly (MEA) for the PEM electrolyzer to increase cell efficiency. However, these membranes suffered from significant gas permeation consequently resulting in an explosion by the combination of hydrogen and oxygen, especially in the high-pressure operation. Many publications employed platinum as a recombination catalyst for reducing hydrogen concentration in the oxygen product stream to ensure safe operation [1-4]. Beside, Pt could be coated on oxidated Ti porous transport layer (PTL) to improve contact resistance between Iridium-based electrode and PTL [5]. In this work, a thin layer of platinum was sputtered on the surface of a low-loading anode (0.5 mgIr/cm2). Three MEAs prepared from commercial hydrous IrOx catalyst with 3 different loadings (1 mgIr/cm2, 2 mgIr/cm2and 3 mgIr/cm2) were used as reference. SEM images of Pt-sputtered MEA showed that the Pt layer had a thickness of approximately 80 nm corresponding to a loading of 0.4 mgPt/cm2. The electrochemical performance of Pt-sputtered MEA was significantly higher than that of bare MEA with 1 and 2 mgIr/cm2. The better performance of MEA with the presence of Pt is due to the improvement in contact resistance between the catalyst layer and PTL, in which lower HFR can be seen. In addition, its performance was comparable to high-loading MEA, while the total amount of precious metal was much lower (0.9 and 3 mg/cm2, respectively). The sputtered MEA also exhibited a slight difference in kinetic resistance compared to pristine MEA. On the other hand, the MEA with the addition of Pt shows a lower concentration of hydrogen in the oxygen product stream compared to pristine MEA at ambient pressure.[1] C. Klose et al., "Membrane interlayer with Pt recombination particles for reduction of the anodic hydrogen content in PEM water electrolysis," Journal of The Electrochemical Society, vol. 165, no. 16, p. F1271, 2018.[2] N. Briguglio, F. Pantò, S. Siracusano, and A. Aricò, "Enhanced performance of a PtCo recombination catalyst for reducing the H2 concentration in the O2 stream of a PEM electrolysis cell in the presence of a thin membrane and a high differential pressure," Electrochimica Acta, vol. 344, p. 136153, 2020.[3] S. Garbe, E. Samulesson, T. J. Schmidt, and L. Gubler, "Comparison of Pt-Doped Membranes for Gas Crossover Suppression in Polymer Electrolyte Water Electrolysis," Journal of The Electrochemical Society, vol. 168, no. 10, p. 104502, 2021.[4] A. Stähler, M. Stähler, F. Scheepers, W. Lehnert, and M. Carmo, "Scalable Implementation of Recombination Catalyst Layers to Mitigate Gas Crossover in PEM Water Electrolyzers," Journal of The Electrochemical Society, vol. 169, no. 3, p. 034522, 2022.[5] M. Bernt et al., "Effect of the IrOx Conductivity on the Anode Electrode/Porous Transport Layer Interfacial Resistance in PEM Water Electrolyzers," Journal of The Electrochemical Society, vol. 168, no. 8, p. 084513, 2021. Figure 1

Operando Measurement of Hydrogen Crossover in Proton Exchange Membrane Electrolysis Cells at Differential Pressures

Low temperature water electrolysis (LTE) using proton exchange membrane electrolysis cells (PEMECs) is a promising approach for producing green H2 that can use electricity from renewable sources. In practice, H2 is stored and dispensed at high pressures. To alleviate efficiency losses associated with pressurizing the product hydrogen, PEMECs can be operated at high differential pressures, e.g., >30bar on the cathode side. However, high differential pressure operation can result in undesirable H2 crossover to the anode (O2) side. This not only reduces the Faradaic efficiency of the cell, but also can result in flammability hazards. H2 crossover in PEMECs is a function of both materials properties such as membrane thickness, water uptake, and permeability, and operating conditions such as temperature, differential pressure, and current density. Example data are shown in Figure 1. While thinner membranes are susceptible to higher H2 crossover rates, they are a desirable material to use because they can result in significantly improved cell performance and lower material and production costs. To mitigate safety concerns related to H2 crossover, gas recombination catalyst (GRC) layers can be introduced into the membrane electrode assembly. The GRCs will react the crossover H2 with O2 to produce water, thereby minimizing the amount of H2 entering the O2 stream. In this talk we will present data from operando crossover measurements of PEMECs employing a variety of membrane materials, both with and without GRCs. The experiments are complimented by modeling results that allow further insights into the processes at hand. Multiple temperatures, differential pressures, and current densities are studied. The results will investigate the tradeoff between performance and capturable H2 production that occurs when thinner membranes are used, and how this effect responds to differential pressure operation. Figure 1

Ventilation Systems in Wetland Plant Species

Molecular oxygen and carbon dioxide may be limited for aquatic plants, but they have various mechanisms for acquiring these gases from the atmosphere, soil, or metabolic processes. The most common adaptations of aquatic plants involve various aerenchymatic structures, which occur in various organs, and enable the throughflow of gases. These gases can be transferred in emergent plants by molecular diffusion, pressurized gas flow, and Venturi-induced convection. In submerged species, the direct exchange of gases between submerged above-ground tissues and water occurs, as well as the transfer of gases via aerenchyma. Photosynthetic O2 streams to the rhizosphere, while soil CO2 streams towards leaves where it may be used for photosynthesis. In floating-leaved plants anchored in the anoxic sediment, two strategies have developed. In water lilies, air enters through the stomata of young leaves, and streams through channels towards rhizomes and roots, and back through older leaves, while in lotus, two-way flow in separate air canals in the petioles occurs. In Nypa Steck palm, aeration takes place via leaf bases with lenticels. Mangroves solve the problem of oxygen shortage with root structures such as pneumatophores, knee roots, and stilt roots. Some grasses have layers of air on hydrophobic leaf surfaces, which can improve the exchange of gases during submergence. Air spaces in wetland species also facilitate the release of greenhouse gases, with CH4 and N2O released from anoxic soil, which has important implications for global warming.

Integration of molten carbonate fuel cell and chemical looping air separation for high-efficient power generation and CO2 capture

Molten carbonate fuel cell (MCFC) allows concentrating the CO2 from the cathode side to the anode side, generating electricity concurrently. Chemical looping air separation (CLAS) can produce an O2 and CO2 mixture stream as cathode feeding gas of MCFC. In this paper, a natural gas-fueled MCFC with internal reforming is integrated with CLAS as O2 and CO2 source for high-efficient power generation with CO2 capture. An O2 and CO2 mixture stream is produced from CLAS by recirculating a portion of CO2-rich flue gas after the afterburner to CLAS. The system is analyzed through thermodynamic and economic performance. At the baseline case, the plant net power efficiency is 59.5%, with 99.9% CO2 capture rate. Based on sensitivity analysis, the higher fuel cell temperature and fuel utilization factor can increase the plant net power efficiency, while the steam carbon ratio and the CLAS reduction reactor temperature are preferable to be at lower levels for higher plant net power efficiency. Finally, economic analysis is conducted. With a MCFC specific cost of $1327/kW and a natural gas price of $2.79/million Btu, the cost of electricity (COE) is $0.094/kWh. The results show the proposed system is attractive for natural gas-fueled power generation with CO2 capture.

MICRO-CHANNEL REACTOR FOR LOW LEVEL H2 OXIDATION WITHIN AN O2 STREAM: PRELIMINARY TESTS IN VIEW OF INTEGRATION IN A H2 GENERATOR WITHIN CECE PROCESS

CECE (Combined Electrolysis Catalytic Exchange) process is the candidate for low level tritiated water detritiation within any application. The process consists mainly of a H2 generator, a LPCE (Liquid Phase Catalytic Exchange) column and an O2 striping column. During operation, tritium is being accumulated within the H2 generator in the form of tritiated water and the effluent streams (hydrogen and oxygen) show in time an increase concentration in tritium in the form of both tritiated water vapors and gas, which needs to be recovered. The tritium in the H2 stream is recovered in a LPCE column, while the tritium in the O2 stream is recovered in a striping column. In view of lowering the load onto the striping column and to recover the tritium in gas form, a micro-channel reactor is proposed to be included for H2 oxidation followed by vapor recovery. The design of the equipment together with the preliminary results of the tests done with H2 and air will be shown, prior to integration in the CECE process.

Optimizing Power in Solid Oxide Electrolysis Systems for Lunar H2 and O2 Production

Producing H2 and O2 propellants from icy regolith in the permanently shadowed regions (PSR) of the moon requires development of integrated robust electrolysis systems that operate in cryogenic environments. High-temperature solid-oxide electrolysis (SOXE) stack technology for water splitting with an optimized balance-of-plant to recuperate heat can provide high-purity H2 (after cooling and drying) and O2 (after cooling) for use as rocket propellant. SOXE steam electrolysis can require below 45 kWhelec kgH2 -1, less than alkaline and PEM liquid H2O electrolyzers. However, to achieve these energy advantages, SOXE systems require efficient upstream steam generation and compression, heat recuperation, and water recovery from the H2 product. In this study, optimization of a 3.5 kWelec lab-scale system reveals that the ability of OxEon’s stack technology to operate at steam-utilizations e H2O > 95% can provide a system that meets the target of 45 kWhelec kgH2 -1.The SOXE stack utilizes stabilized zirconia electrolytes similar to the MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment) system and operates at a steady 800ºC. This high operating temperature requires efficient thermal integration and balance-of-plant components to minimize system energy and mass for operation in the PSRs ‘cryo-vac’ conditions, where temperatures can reach as low as 40 K. Figure 1a illustrates the process diagram showing the steam generator, compressor, cathode and anode heat recuperators for heat recovery, and a H2 cooler/dryer for exhaust H2O recovery. Passive radiative coolers for lunar operation prepare the O2 and H2 product streams for liquification. To optimize the system operation, a MATLAB-based process model calculates the performance of the integrated component system model and is called by the MATLAB optimization toolbox to minimize specific power w sp under constraints that maintain reasonable system mass. Optimization variables in this study included SOXE stack H2O utilization e H2O; SOXE stack anode electrochemical compression DP a; steam generator vapor outlet temperature T vap; and compressor pressure ratio P rat. The SOXE cell operated at the thermoneutral voltage (V tn » 1.28 V/cell @ 800℃). BOP power demands included the compressor, SOXE steam preheater, insulation heaters, and supplemental electric heating for the steam generator. Optimization for the 3.5 kWelecSOXE system indicates that the biggest benefit for w sp comes from high eH2O, which reduces freezing required to recover water in the H2 passive cooler. e H2O of 95% with lower T vap around 85℃ and low P rat (around 2.00) provides a path for achieving the target w sp < 45 kWhelec kgH2 -1 . Figure 1

In-Operando Measurement of Hydrogen Crossover in Proton Exchange Membrane Electrolysis Cells at Differential Pressures

Low temperature water electrolysis (LTE) using proton exchange membrane electrolysis cells (PEMECs) is a promising approach for producing green H2 that can use electricity from renewable sources. In practice, H2 is stored and dispensed at high pressures. To alleviate efficiency losses associated with pressurizing the product hydrogen, PEMECs can be operated at high differential pressures, e.g., >30bar on the cathode side. However, high differential pressure operation can result in undesirable H2 crossover to the anode (O2) side. This not only reduces the Faradaic efficiency of the cell, but also can result in flammability hazards. H2 crossover in PEMECs is a function of both materials properties such as membrane thickness, water uptake, and permeability, and operating conditions such as temperature, differential pressure, and current density. Example data are shown in Figure 1. While thinner membranes are susceptible to higher H2 crossover rates, they are a desirable material to use because they can result in significantly improved cell performance and lower material and production costs. To mitigate safety concerns related to H2 crossover, gas recombination catalyst (GRC) layers can be introduced into the membrane electrode assembly. The GRCs will react the crossover H2 with O2 to produce water, thereby minimizing the amount of H2 entering the O2 stream. In this talk we will present data from in-operando crossover measurements of PEMECs employing a variety of membrane materials, both with and without GRCs. The experiments are complimented by modeling results that allow further insights into the processes at hand. Multiple temperatures, differential pressures, and current densities are studied. The results will investigate the tradeoff between performance and capturable H2 production that occurs when thinner membranes are used, and how this effect responds to differential pressure operation. Figure 1

Gas Pulse-X-Ray Probe Ambient Pressure Photoelectron Spectroscopy with Submillisecond Time Resolution.

A setup capable of conducting gas pulse–X-ray probe ambient pressure photoelectron spectroscopy with high time resolution is presented. The setup makes use of a fast valve that creates gas pulses with an internal pressure in the mbar range and a rising edge of few hundreds of microseconds. A gated detector based on a fast camera is synchronized with the valve operation to measure X-ray photoemission spectra with up to 20 μs time resolution. The setup is characterized in several experiments in which the N2 gas is pulsed either into vacuum or a constant flow of another gas. The observed width of the pulse rising edge is 80 μs, and the maximum internal pulse pressure is ∼1 mbar. The CO oxidation reaction over Pt (111) was used to demonstrate the capability of the setup to correlate the gas phase composition with that of the surface during transient supply of CO gas into an O2 stream. Thus, formation of both chemisorbed and oxide oxygen species was observed prior to CO gas perturbation. Also, the data indicated that both the Langmuir–Hinshelwood and Mars-van-Krevelen mechanisms play an important role in the oxidation of carbon monoxide under ambient conditions.

Solid Oxide Electrolysis System Optimization for Lunar Production of H2 and O2

Remote sensing spacecraft have located extensive surface ice in lunar permanently shadowed regions (PSRs) associated with craters near the poles. Producing H2 and O2 propellants from icy regolith in these regions requires development of integrated, robust electrolysis systems capable of operating in cryogenic environments. This team is demonstrating the feasibility of propellant production from lunar ice using high-temperature solid-oxide electrolysis (SOXE) and an optimized integrated balance-of-plant (BOP). High-temperature steam electrolysis has an efficiency advantage over PEM and alkaline electrolyzers, requiring less than 45 kWhelec kgH2 -1 [1], much less than liquid-phase electrolysis. SOXE systems require efficient steam generation and compression, heat recuperation, and subsequent drying of the H2 product stream. In this study, optimization of a demonstration system using less than 4.0 kWelec is based on OxEon’s SOXE stack that can deliver exceptionally high steam-utilization, (U H2O > 95%) and direct electrochemical O2 compression to facilitate O2 liquification with passive cooling at lunar PSR temperatures. This optimization forms the basis for the implementation of a lab-scale system for testing in a cryo-vac chamber, in order to demonstrate the viability of the optimized system for potential further, flight-scale development.The SOXE stack utilizes rare-earth stabilized zirconia electrolyte similar to technology in the MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment) system [2]. The stack operates at 800ºC to balance trade-offs between area-specific resistance (ASR) and degradation. The 800ºC operating temperature requires efficient thermal integration of BOP to minimize specific energy and mass for reliable operation in the PSRs’ ‘cryo-vac’ conditions, where temperatures can reach as low as 40 K. This study shows how high U H2O enables optimization of the BOP components for system designs that can operate in the cryo-vacuum conditions with specific power w sp < 45 kWhelec kgH2 -1.Figure 1a illustrates principal BOP components including a steam generator, a compressor, cathode and anode heat recuperators, and a H2cooler/dryer. Passive radiative coolers for lunar operation prepare exhaust O2 and H2 product streams for liquification. The team developed a MATLAB-based process model to optimize the system configuration and operation. Performance of the stack, heat exchangers, and compressor are parameterized with both design parameters and system operating conditions that served as optimization variables. The system model is called by the MATLAB function ‘fmincon’ to minimize w sp under constraints that maintain reasonable system mass.The optimization study fixes H2 production rate at 0.075 kg H2 h-1 for the demonstration system in the lab-scale cryo-vac chamber. Optimization variables n this study for this lab-scale prototype system include 1) SOXE stack steam utilization U H2O ; 2) SOXE stack anode electrochemical compression DP a, for the O2 exhaust pressure; 3) steam generator vapor outlet temperature T vap; 4) compressor (scroll) pressure ratio P rat; and 5) inlet steam mass-flow split between recuperators. The SOXE electrolysis stack has a fixed cell area (110.8 cm2) and an experimentally measured area specific resistance (ASR). An electric preheater for the flow out of the cathode recuperator set the inlet steam flow to the 800 ℃ operating temperature, and this preheater added to the power (and thus specific work) required for the system. The SOXE cell operates at the thermoneutral voltage (V tn ≈ 1.28 V/cell @ 800℃) and stack current I tot is proportional to (V tn – V OCV)/ASR, where V OCV, open-circuit voltage, increases with U H2O. Primary BOP power demands include the compressor motor, SOXE stack steam preheater, thermal enclosure heater, and supplemental electric heating for the steam generator, but overall, the stack represented more than 80% of total power demand.Optimization of the system operating at 0.075 kg H2 h-1 shows that w sp had the highest sensitivity to U H2O with values above 0.85 required to achieve w sp < 45 kWhelec kgH2 -1 as shown in the contour plots of Figures 1b and 1c. Minimizing w sp encourages lower compressor pressure ratiosP rat which is limited to a minimum of 2.0. Increasing the steam generator temperature reduces compressor power demand but increases supplemental electrical heating for the steam generation, Thus, steam generator outlet temperature has minimal impact on w sp as shown in Figure 1c. Electrochemical compression of the O2 anode product does not benefit w sp, but it will greatly reduce the O2 passive cooler size which reduces mass/costs for a lunar deployed system. Additional studies are ongoing to look at trade-offs between system mass and system power with an eye toward optimizing both cost and reliability in a full-scale lunar deployed system. References Poszdeich, K. Schwarze, and J. Brabandt, Intl. J. Hydrogen Energy, 44(35), 19089-19101, 2019.Hartvigsen, S. Elangovan, J. Elwell, and D. Larsen, ECS Trans., 78(1), 2953-2963, 2017. Figure 1

Thermochemical solar-driven reduction of CO2 into separate streams of CO and O2 via an isothermal oxygen-conducting ceria membrane reactor

• Demonstration of single-step CO 2 thermolysis in a novel solar-driven membrane reactor. • In-situ separation of CO and O 2 via lattice oxygen transfer through ceria dense membrane. • Continuous and isothermal operation of the MIEC tubular membrane reactor at 1450–1550 °C. • Increasing the temperature, CO 2 concentration or flow rate enhanced CO and O 2 production rates. • The fuel production rate was up to 4.26 μmol/cm 2 /min at 1550 °C under pure CO 2 feeding. CO 2 single-step thermolysis was achieved using oxygen permeable MIEC (mixed ionic-electronic conducting) membranes made of ceria for separate production of CO on the feed side and O 2 on the sweep side. The CO 2 -dissociation reaction was driven by concentrated solar energy as a renewable thermal energy source and by applying a chemical potential gradient between both membrane sides. A continuous oxygen transfer across the membrane was achieved thanks to a flow of inert gas on the permeate side. This created the required oxygen partial pressure gradient and favored oxygen permeation via oxygen ion diffusion through the ceria membrane thickness. A novel solar chemical reactor integrating the reactive ceria membrane was designed and tested under real concentrated solar radiation, with operating temperatures up to 1550 °C. The reactive part of the tubular redox membrane was located inside a well-insulated cavity receiver for homogeneous heating, which was fed with a carrier argon flow on the sweep side to facilitate the transport and removal of the permeated oxygen. The dynamic response of the solar fuel production upon changing the operating conditions (temperature, CO 2 mole fraction, and feed gas flow rate) in the membrane reactor was investigated by quantifying the evolved gas production rates. Continuous CO 2 dissociation was achieved on the feed side inside the tubular membrane with in-situ spatial separation of O 2 and CO streams across the membrane. Reliable solar membrane reactor operation under real concentrated sunlight was successfully demonstrated for the first time, with stable and unprecedented CO production rates up to 0.071 μmol/cm 2 /s at 1550 °C and CO/O 2 ratio of 2.

Single-Walled Carbon Nanotube Supported PtNi Nanoparticles(PtNi@SWCNT) Catalyzed Oxidation of Benzyl Alcohols to the Benzaldehyde Derivatives inOxygen Atmosphere

This study reports a developed process which is a general and facilemethod for the oxidation of benzyl alcohol (BnOH) compounds to the benzaldehyde (BA)derivatives, under mild conditions. The oxidation of BnOH species catalyzed byPtNi@SWCNT in toluene (3 ml) at 80 °C under a continuous stream ofO2. Single wall carbon nanotube supported PtNi(PtNi@SWCNT) nanoparticles were synthesized using a single-step modified reductionprocess. The characterization of PtNi@SWCNT nanocatalyst was performed bytransmission electron microscope (TEM), X-ray diffraction (XRD), X-ray PhotoelectronSpectroscopy (XPS), and elemental analysis by ICP-OES. A variety of BnOH compoundswere oxidized by the PtNi@SWCNT catalyst and all the expected oxidation productswere obtained in high efficiency in 2 hours of reaction time. TLC was used tomonitoring the reaction progress, and the products were identified by1H/13C-NMRanalysis.

Drifts (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) - a Way to Assess the Reactivity of Solid Electrolytes with Ambient Air

All-Solid-State-Batteries (ASSBs) are envisioned to be the next-generation lithium-ion batteries (LIBs). Replacing the inflammable organic electrolyte in conventional liquid electrolyte LIBs by a non-inflammable inorganic solid electrolyte (SE) is one of the concepts to increase battery safety. Moreover, ASSBs may offer higher gravimetric and volumetric energy density compared to liquid electrolyte based technology.[1,2] However, their high reactivity with ambient air is a major obstacle which prevents ASSBs from industrial scale processing, as production under inert atmosphere is not possible on this level.[3] Thus, industrial ASSB production would have to take place in dry-rooms, leading to the question whether SE handling in dry-room atmospheres containing O2 and CO2 and ppm-levels of moisture is possible.Therefore, we will examine the reactivity of the commercially available solid electrolyte Li10SnP2S12 (LSPS) with O2 and CO2 as well as with the typical H2O concentration in ambient air, followed by reactivity studies with a mixture of CO2 and H2O vapor. For this purpose, we used Diffuse Reflectance Infrared Fourier-Transform Spectroscopy (DRIFTS), a highly surface sensitive infrared technique.The hermetically sealed DRIFTS cell containing the SE powder was set up such that it could be purged with dry or humidified streams of inert gas (Ar), O2, and CO2, or mixtures thereof while monitoring in situ the chemical changes of the LSPS solid electrolyte and the formed gaseous species by DRIFTS. Figure 1 shows stacked IR spectra of LSPS after exposure to different gasses, stating no reactivity with O2 or CO2 but noticeable changes in the IR spectrum for exposure to moisture and a combination of CO2 and moisture, respectively, indicating decomposition reactions.The spectral analysis of the decomposition process is supported by ex situ X-Ray Diffractometry (XRD) analysis of the LSPS powder after exposure to the different gas streams. Concluding, the impact of exposing LSPS to the above mentioned gas mixtures on the ionic conductivity of the solid electrolyte will be demonstrated. Acknowledgements: This work was carried out as part of the research project ASSB coordinated by ZAE Bayern. The project is funded by the Bavarian Ministry of Economic Affairs, Regional Development and Energy.

Enhanced performance of a PtCo recombination catalyst for reducing the H2 concentration in the O2 stream of a PEM electrolysis cell in the presence of a thin membrane and a high differential pressure

High electrochemical efficiency at elevated current densities and low H2 concentration in O2 can be achieved in PEM electrolysis using thin membrane and integrated recombination catalyst. An enhanced PtCo alloy recombination catalyst was synthesized and used at the anode of a membrane-electrode assembly (MEA). This allowed reducing the H2 concentration in the oxygen stream during electrolysis operation with a thin 50 μm perfluorosulfonic acid (PFSA) Aquivion® membrane. Both dual-layer and composite anode configurations (PtCo/IrRuOx) were investigated. The electrochemical performance of the MEAs containing the recombination catalyst was better than a bare MEA while producing a decrease of the H2 content at the anode. This allowed extending the partial load operation down to 5% at 55 °C under a differential pressure of 20 bar. The effects of the cathodic pressure and cell temperature (including evaluation of intermediate temperature operation at 140 °C) on both electrochemical performance and H2 concentration in the anode stream were investigated. An excellent performance of 4 A cm−2 at 1.75 V, at 140 °C, 20 bar cathode pressure, 5.5 bar anode pressure, with 0.6 mg cm−2 overall precious metal catalysts content was recorded. At 140 °C, the MEA also showed a moderate H2 concentration in O2 of about 2.3%, almost constant through most of the current density range.

Handy and highly efficient oxidation of benzylic alcohols to the benzaldehyde derivatives using heterogeneous Pd/AlO(OH) nanoparticles in solvent-free conditions

The selective oxidation of benzylic alcohols was performed by using commercially available aluminum oxy-hydroxide-supported palladium (Pd/AlO(OH)) nanoparticles (0.5 wt.% Pd, about 3 nm size) under mild conditions. The oxidation method comprises the oxidation of benzyl alcohols catalyzed by aluminum oxy-hydroxide-supported palladium under ultrasonic and solvent-free conditions and a continuous stream of O2. The characterization of aluminum oxy-hydroxide-supported palladium nanocatalyst was conducted by several advanced analytical techniques including scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and elemental analysis by ICP-OES. The oxidation of a variety of benzyl alcohol compounds were tested by the aluminum oxy-hydroxide-supported palladium nanoparticles, and all expected oxidation products were obtained by the high conversion yields within 3 hours. The reaction progress was monitored by TLC (Thin-layer chromatography), and the yields of the products were determined by 1H-NMR and 13C NMR analysis.

Experimental study of Cu-modified manganese ore for O2 production in the CLC + CLOU scheme

In chemical looping combustion (CLC), a necessary oxygen polishing step exerted an additional cost to the technology due to an extra demand of pure O2. However, the additional cost can be lowered if the oxygen carriers can produce gaseous oxygen, i.e. has a chemical looping with oxygen uncoupling (CLOU) property. A CLC + CLOU scheme is proposed in the study. Production of gaseous O2 using a manganese ore and the Cu-modified manganese ore as oxygen carriers were investigated. The reaction kinetics of the two oxygen carriers were studied by thermogravimetric analysis (TGA). Multiple O2 uptake and release cycles were carried out to demonstrate the good stability of the oxygen carriers. Continuous tests with both oxygen carriers were carried out in a dual fluidized bed. Results showed that both oxygen carriers could be fluidized well in the continuous run and a stream of O2 could be obtained stably. The Cu-modified manganese ore showed higher oxidation rate and oxygen transport capacity than the original manganese ore. Both materials have advantage economically and could be promising for O2 production in the CLC + CLOU scheme.