Anode Production Research Articles

Electrolytic Processing of Pb-Bi Alloy

Metal bismuth is mainly produced as a by-product in the production of lead, tungsten, copper, silver, gold, tin and zinc. Approximately 90 % of all extracted bismuth is obtained from lead, copper and other concentrates. The main source of bismuth is lead concentrates obtained during the processing of lead, as well as lead-zinc and other polymetallic ores. During the processing of these concentrates, bismuth almost completely enters the rough lead, from which it is removed during its refining. The most common technologies for the recovery of bismuth from lead ingots are the Kroll-Betterton process and the Betts electrolytic process. During the electrolysis of the Bi-Pb alloy, the separation of three products has been established, they are anode and cathode alloys, as well as salt melt. The complexity of pyroelectrometallurgical processing of a bismuth-poor alloy with the production of rough bismuth in one stage is confirmed, which necessitates the use of two stages of electrolysis. At the first stage of electrolysis, the anode product‑1 (17.3–48.5 % of the initial Pb-Bi alloy) of the composition has been isolated,%: 16.6–48.4 Bi; 51.4–83.2 Pb; operational extraction,%: 92.2–96.6 Bi; 9.8–44.4 Pb; main phases Bi0,3Pb0,7 and Bi0,95Pb0,05. A six-fold bismuth enrichment is achieved in the anode product. At the second stage of electrolysis of the previously isolated anode product of the composition,%: 26.7 Bi; 73.1 Pb; 0.13 Cu; 0.08 Zn, the anode product‑2 (28.1 % of the enriched Pb-Bi alloy) of the composition has been separated,%: 93.6 Bi; 4.1 Pb; 0.086 Ag; 0.0066 As; 0.006 Sb; 0.0013 Cu; 0.001 Sn; 0.0014 Zn; stage extraction,%: 98.6 Bi; 1.6 Pb; main phase Bi0,95Pb0,05. As a result of pyroelectrometallurgical processing of a Pb-Bi alloy (~10 % Bi) with anode polarization in two stages, an anode product (8.7 % of the initial alloy) of the composition has been isolated,%: ≥ 93.6 Bi; 4.1 Pb; extraction from the initial alloy,%: 93.0 Bi; 0.4 Pb has been obtained. The following modes are recommended for pyroelectrometallurgical processing in two stages of Pb-Bi alloy: process temperature 550–600 °C; anode current density: 0.5 A/cm2 at the first stage; 0.2–0.3 A/cm2 at the second stage; cathode current density: 1.5 A/cm2 at the first stage; 1.0 A/cm2 at the second stage; operating voltage on the tub: at the first stage 8–12 V; at the second stage 5–8 V; the composition of the electrolyte at both stages,%: 7 NaCl; 35 KCl; 18 PbCl2; 40 ZnCl2; the amount of electrolyte output for processing: at the first stage – 10 % of the mass of the Pb-Bi alloy after alkaline treatment; at the second stage – 10 % of the mass of the anode product of the first stage

Liquid lithium metal processing into ultrathin metal anodes for solid state batteries

Lithium metal anodes are among the most promising candidates for further increasing the energy density of lithium ion batteries and all-solid-state batteries. A reduction of the anode thickness by using ultrathin lithium metal films is a crucial requirement to achieve a significant overall reduction of thickness on cell level. However, besides anode stabilization, realizing scalable technologies for an efficient production of thin lithium metal anodes is one of the most challenging obstacles for the success of various next-generation battery chemistries. In this publication we introduce a disruptive lithium melt deposition process for thin lithium metal coating on thin copper current collector foils. The wetting of molten lithium on the substrate can only be achieved through a lithiophilic interlayer. As a result fast and homogeneous lithium spreading on the substrate is enabled allowing roll-to-roll coating with liquid-deposition technologies as demonstrated in this contribution with a speed of several meters per minute and reaching 100 mm width. With this new process the anode thickness can be tuned in a wide range (1–30 µm). Evaluation in a prototype solid battery system shows high electrochemical lithium utilization and no detrimental effects compared to commercially available lithium reference foils.

Efficient electrolysis of 5-hydroxymethylfurfural to the biopolymer-precursor furandicarboxylic acid in a zero-gap MEA-type electrolyzer

Replacement of today’s established chemical production processes by “green” sustainable alternatives has become a scientific priority. The oxidative conversion of 5-hydroxymethylfurfural (5-HMF) to the biopolymer component 2.5-furandicarboxylic acid paired with green electrolytic hydrogen production is a promising emerging green process. Here, we present a family of active selective and stable interlayer anion-tuned NiX (X = Fe, Mn, Co, V) bimetallic-layered, double-hydroxide catalysts for the selective oxidation of 5-HMF to 2.5-furandicarboxylic acid in a zero-gap MEA-type electrolyzer. We report that tuning the structural interlayer distance of the catalyst by anion exchange gives rise to previously unachieved catalytic performance for the anodic production of the biopolymer building block. Operando differential electrochemical mass spectrometry analysis reveals the electrode window for the perfectly selective HMF conversion. The role of the catalyst dopants, their real surface areas, the stability of the catalytic interface, and aspects of its favorable techno-economics are discussed. • Active, selective, and stable interlayer anion-tuned catalyst for biomass oxidation • Operating in a zero-gap MEA-type single electrolyzer cell • Operando analysis revealed the perfectly selective HMF conversion window Strasser et al. present a family of active selective and stable Ni-based catalysts for the selective oxidation of biomass in an electrolyzer. The biomass electrolysis device yields previously unachieved production of a biopolymer precursor and may offer techno-economic cost advantages.

Anode biofilm maturation time, stable cell performance time, and time-course electrochemistry in a single-chamber microbial fuel cell with a brush-anode

For accurate and reproducible MFC experiments, it is important to know when MFCs produce stable cell performance. Herein, four replicate single-chamber MFCs were tested for 17 weeks by using polarization and cyclic voltammetry (CV) tests. The strong MFCs (#2,4,3) showing continuous performance enhancement initially (3rd–9th week) produced good subsequent performance (9th–17th week). The weak MFC-1 experienced a performance drop initially and showed bad subsequent performance. All the MFC performance became stable after 9 weeks. The strong MFCs produced power 2.8–3.6 times higher and anode resistance 7.5–23.9 times lower than the weak. However, their cathode resistances were similar. CV results showed anodic current production increased continuously in all MFCs, indicating anode biofilms kept growing;, MFC performance did not increase accordingly. Anodic CVs had a typical S-shape curve, but those of MFC-1 showed straight lines from the 9th week. The weak MFC-1 showed smaller CV currents and thinner CV curves than those of the strong MFCs. In MFC-1, at the 17th week, the anode resistance reduced by 47%, anodic current and cell performance increased. Regression analysis showed anode resistance was a limiting factor of the weak MFC and cathode resistance was that of the strong MFCs. This result suggests one operating principle: improve anodes in weak MFCs and cathodes in strong MFCs to achieve better MFC performance.

In Situ Replacement Synthesis of Co@NCNT Encapsulated CoPt3 @Co2 P Heterojunction Boosting Methanol Oxidation and Hydrogen Evolution.

Simultaneous boosting electrochemical methanol oxidation reaction (MOR) for direct methanol fuel cells and production of hydrogen is meaningful but challenging. Herein, a sea urchin-shaped cobalt-embedded N-doped carbon nanotubes (Co@NCNT) encapsulated CoPt3 @Co2 P heterojunction (CoPt3 @Co2 P/Co@NCNT) is fabricated. Theoretical calculations confirm that electrons at the interfaces transfer from CoPt3 to Co2 P, where electron hole region on CoPt3 is beneficial to improving the MOR activity, whereas accumulation region on Co2 P favors to the optimization of H2 O and H* absorption energies for hydrogen evolution reaction (HER). Benefitting from its interfacial electronic reconfiguration, the CoPt3 @Co2 P/Co@NCNT heterojunction exhibits excellent electrocatalytic performances for MOR and HER, in which the mass activity (2981mAmgPt -1 ) for MOR is 14.2 times than that of Pt/C (20%), and the smallest overpotentials only requires 19 mV to deliver a current density of 10mAcm-2 for HER. Moreover, the electrolyzer employing CoPt3 @Co2 P/Co@NCNT for anodic MOR and cathodic H2 production only requires a low voltage of 1.43 V at 10mAcm-2 with impressive long-life cycling stability, which is obviously better than that of commercial Pt/C//RuO2 . This study offers a novel strategy for other organics oxidation reaction coupled with HER catalyzed production of hydrogen.

Anodic production of hydrogen peroxide using commercial carbon materials

The electrochemical production of hydrogen peroxide (H2O2) from water is an appealing alternative to substitute the classic anthraquinone process. Herein, we show a process development to maximize the efficiency of the anodic production of H2O2. Carbon materials were used as anodes to optimize process parameters such as current density, electrolyte concentration, and the pH. We found that the electrolyte concentration, pH, and the presence of a chemical stabilizer have a substantial effect on the selectivity of water oxidation to H2O2. The addition of Na2SiO3 as a stabilizer increased the H2O2 production significantly at high pH regimes. A direct relationship between CO32− ion activity and enhanced production of H2O2 was also observed. We report H2O2 concentrations in the anolyte up to 33 mmol L−1 at a current density of 100 mA cm−2 using commercial and low-cost carbon fiber paper.

A Molten-Salt Electrolysis Approach for the Recycling of Spent Lithium-Ion Batteries

Recycling spent lithium-ion batteries can close the strategic metal cycle while averting ecological and environmental footprints. High-temperature molten salts could act as both a promising electrolyte and a solvent to recover valuable Li and transition metals assisted by an electrochemical method that use electrons to break down the crystal structure and thereby sperate the Li and transition metal. In this paper, the molten salt paired electrolysis method employs electrons as both reducing and oxidizing agents and the molten salt as the solvent to separate the desired products without producing any hazardous secondary waste. Since the valence of Fe in LiFePO4 is 2+, the valence can be moved at both directions if proper electrolytes are chosen and appropriate potentials are applied. Moreover, molten salt electrolytes have a wide electrochemical potential range (e.g., electrochemical window) and considerable capability for dissolving lithium salt, which can be used as an electrolyzer to entail specific electrochemical reactions and solvent extraction processes. A molten salt electrolyzer with a solid LiFePO4 cathode and three types of anodes. All the three electrolyzers work well to electrochemically split LiFePO4 to Fe, Li+, and PO4 3 −. Besides molten carbonates, other types of molten salts such as halides, hydroxide, sulfates can be used. The anodic products are CO2, O2 and Fe3O4 if graphite, Ni10Cu11Fe alloy and LiFePO4 anodes are employed, respectively. To minimize the energy consumption and CO2 emissions, the paired electrolysis cells with dual LiFePO4 electrodes is preferable. In all types of eletrolyzers, the recovery rates of both Li and Fe are over 95.2%. Beside LiFePO4, the molten-salt electrolysis approach can be used to treat a variety of cathode materials of LIBs.

Electrochemical Ammonia Stripping from Non-Nitrified Animal Rendering Wastewater

Biological nitrogen removal from animal processing wastewater is subject to process disruptions due to high loadings as well as inhibition from disinfectants used in processing. Ammonium removal and recovery from non-nitrified secondary effluent using electrochemical stripping provides a possible alternative for treatment that not only removes nitrogen, but also recovers it. In a water electrolysis cell, pH at the cathode increases as water is reduced to hydrogen gas. Ammonium is, therefore, able to be removed through ammonium/ammonia equilibrium towards ammonia, which can be recovered using gas-permeable membrane. The presence of chloride in the wastewater however may result in anodic production of chlorine, and subsequent formation of toxic disinfection by-products. To achieve ammonium removal and recovery while eliminating chlorine production, the impact of electrochemical cell configuration was evaluated in this study. Cathode-fed cell configurations outperformed anode-fed cells in ammonium treatment. In cathode-fed cells that included a Cl- trap ammonium removal starting with initial concentrations of 1000 mg N/L not only approached 99.9% irrespective of the current density and the counter chamber electrolyte composition, but also resulted in no formation of chlorine at the anode. Ammonium removal in cathode-fed cells that only included a cation exchange membrane although did not result in chlorine formation, showed a strong dependence of ammonium removal on the current density and the salt concentration in the anode chamber. Chlorine production was observed in both the anode-fed cells and the cathode-fed cells that included an AEM to separate the two chambers, with measured concentrations in 4-h batch experiments of 28 mg/L and 14.05 mg/L of free chlorine and 53.25 mg/L and 36.03 mg/L of total chlorine, respectively. Cathode-fed cells with Cl- trap and cathode-fed cells with an AEM needed higher applied voltages for treatment (5.89 V and 5.93 V, respectively, vs. 4.46 V for anode-fed cells). Despite the higher applied voltages, treating non-nitrified animal processing wastewater in cathode-fed cells with a Cl- trap provides several advantages, and presents an opportunity for scale-up of the process.

Effect of Cr Content on Corrosion Resistance of Low-Cr Alloy Steels Studied by Surface and Electrochemical Techniques

The electrochemical behavior of low alloyed Fe-Cr steels with 3 and 5% wt. of Cr in neutral Na2SO4 electrolyte combined with a detailed chemical and morphological characterization of these alloys performed by Auger electron spectroscopy, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and scanning electron microscopy are presented here. The corrosion of low alloyed Fe-Cr steels proceeds in the prepassive range, with the formation of corrosion surface films having a duplex structure with outer iron oxide/hydroxide layer and inner Cr oxide-rich layer. The thickness, composition, and the morphology of the surface films vary as a function of chromium content in the alloy as well as conditions of electrochemical tests (temperature). Even a low chromium content shows a beneficial effect on the corrosion performances of the Fe-Cr steels. The chromium as a more active component than iron of ferrite increases the anodic activity of this phase, which results in a rapid saturation of the surface with the anodic reaction products forming a fine crystalline-like and compact layer of corrosion products. In this way, the chromium acts as a modifier of formation/crystallization of the iron-rich surface film (mainly magnetite) in the prepassive range.

Killing Two Birds with One Stone: Selective Oxidation of Small Organic Molecule as Anodic Reaction to Boost CO2 Electrolysis

Replacing anodic oxygen evolution reaction (OER) with the oxidation of small organic molecules in CO2 electrolysis is an ingenious strategy to reduce the energy consumption while produce valuable anodic products instead of low‐value O2. Herein, an advanced CO2 electrolysis system constructed by replacing OER with selective methanol oxidation reaction (MOR) is reported as a proof‐of‐concept, which achieves the yielding of value‐added products in both cathode and anode. Notably, the MOR over a self‐supported NiCo‐based metal–organic framework‐derived anode (NiCo‐NF‐ET) only needs 1.291 V to reach a high current density of 100 mA cm−2, which is about 346 mV lower than that of OER. Simultaneously, formate can also be produced with the Faradaic efficiencies approaching to 100%. Consequently, in comparison with the conventional CO2 electrolysis system, integrating cathodic CO2 reduction reaction (CO2RR) with anodic MOR can lead to the reduction of about 880 mV to deliver the current density of 30 mA cm−2, while without compromising the selectivity of the products in both electrodes. Herein, the great potential to increase the economic benefits of CO2 electrolysis via the rational design of nonprecious electrocatalysts and participated anodic oxidation reactions is shown.

Integration of ultraviolet irradiation with electrochemical chlorine and hydrogen peroxide production for micropollutant abatement

This research evaluated integrating ultraviolet (UV) irradiation with electrochemical chlorine (Cl2) and/or hydrogen peroxide (H2O2) production for micropollutant abatement in water treatment. Combining UV with anodic Cl2 production (E-UV/Cl2) effectively abated gemfibrozil and naproxen, but ineffectively abated ibuprofen due to its low reactivity with chlorine radicals (e.g., ClO• and Cl2-•). In comparison, combining UV with cathodic H2O2 production (E-UV/H2O2) more effectively abated ibuprofen, but less efficiently abated gemfibrozil and naproxen due to the significant scavenging of •OH by the water matrix. Moreover, simultaneously producing Cl2 and H2O2 during UV irradiation (E-UV/Cl2/H2O2) in an undivided reactor did not further enhance micropollutant abatement compared to the E-UV/H2O2 process because of the mutual consumption of anodically generated Cl2 and cathodic generated H2O2. In contrast, by separating the anodic and cathodic compartments with an anion exchange membrane and operating the E-UV/Cl2/H2O2 process in an anode-to-cathode configuration, all test micropollutants could be adequately abated through the sequential oxidation with the selective chlorine radicals and non-selective •OH in the anodic and cathodic compartments. In general, the concentrations of micropollutants could be abated by 84–100% with a short hydraulic residence time (HRT) of 9.4 min and feasible energy demand (EEO ≤ 3.15 kWh/m3-log) in the selected groundwater and secondary wastewater during the E-UV/Cl2/H2O2 process in the divided reactor. The results indicate that different synergistic effects can be obtained for micropollutant abatement by combining UV and electrochemical processes in varying configurations, and the divided E-UV/Cl2/H2O2 process is a more robust and energy-efficient method for micropollutant abatement during decentralized water treatment.

Electrocatalytic Glycerol Oxidation with Concurrent Hydrogen Evolution Utilizing an Efficient MoOx /Pt Catalyst.

Glycerol electrolysis affords a green and energetically favorable route for the production of value-added chemicals at the anode and H2 production in parallel at the cathode. Here, a facile method for trapping Pt nanoparticles at oxygen vacancies of molybdenum oxide (MoOx ) nanosheets, yielding a high-performance MoOx /Pt composite electrocatalyst for both the glycerol oxidation reaction (GOR) and the hydrogen evolution reaction (HER) in alkaline electrolytes, is reported. Combined electrochemical experiments and theoretical calculations reveal the important role of MoOx nanosheets for the adsorption of glycerol molecules in GOR and the dissociation of water molecules in HER, as well as the strong electronic interaction with Pt. The MoOx /Pt composite thus significantly enhances the specific mass activity of Pt and the kinetics for both reactions. With MoOx /Pt electrodes serving as both cathode and anode, two-electrode glycerol electrolysis is achieved at a cell voltage of 0.70V to reach a current density of 10mA cm-2 , which is 0.90V less than that required for water electrolysis.

Effect of Particle Size Distributions and Shapes on the Failure Behavior of Dry Coke Aggregates.

Carbon anodes participate in chemical reactions to reduce alumina in the Hall–Héroult process, of which coke aggregates make up a major part. The failure analysis of coke aggregates not only leads to a better understanding of the deformation mechanisms of anode paste under compressive loading but also can identify potential causes of structural defects in carbon anodes, such as horizontal cracks. The coke aggregates are composed of particles with different size distributions and shapes, which may strongly affect the failure behavior of the anode during compaction. In this paper, the effects of particle size distributions and shapes on the mechanical behavior and the failure of coke aggregates are investigated using the discrete element method modeling technique. The numerical results reveal that, although the mechanical behavior of coke mixtures is generally dependent on larger particles, the presence of fine particles in the coke aggregates reduces fluctuations in the stress–strain diagram. In addition, the rolling resistance model is employed as a parameter representing the effect of particle shape. It is shown that the rolling resistance model can be an alternative to the overlapped spheres model, which has a higher computational cost than the rolling resistance model. The second-order work criterion is used to evaluate the stability of the coke aggregates, the results of which indicate that the addition of fine particles as well as increasing the rolling resistance between the particles increases the stability range of the coke aggregates. Moreover, by using the analysis of micro-strain contour evaluations during the compaction process, it is shown that, both by adding fine particles to the coke mixture and by increasing the rolling resistance between the particles, the possibility of creating a compression band in the coke aggregates is reduced. Since the presence of the compaction bands in the anode paste creates an area prone to horizontal crack generations, the results of this study could lead to the production of carbon anodes with fewer structural defects.

Modeling of Thermo-Chemo-Mechanical Properties of Anode Mixture during the Baking Process.

In the Hall–Héroult process, prebaked carbon anodes are utilized to produce primary aluminium. The quality of the anode plays a crucial role in the efficiency of electrowinning primary aluminium. In the production of anodes, the anode baking is considered as the stage most frequently causing anode problems. During the baking process, the anode undergoes complex physicochemical transformations. Moreover, the anode at a lower position, imposed by loading pressures from upper anodes, will creep during this process. Thus, the production of high-quality anodes demands efficient control of their baking process. This paper aims to investigate the thermo-chemo-mechanical properties of the anode paste mixture at high temperatures. These properties include kinetic parameters of pitch pyrolysis such as the activation energy and the pre-exponential factor, the thermal expansion coefficient (TEC) and relevant mechanical parameters related to the elastic, the viscoelastic and the viscoplastic behaviours of the anode. For this purpose, experiments consisting of the thermogravimetric analysis, the dilatometry and the creep test were carried out. Based on the obtained results, the forementioned parameters were identified. Relevant mechanical parameters were expressed as a function of a new variable, called the shrinking index, which is related to the volatile released in open and closed pores of the anode. This variable would be used to highlight the chemo-mechanical coupling effect of the anode mixture. New insights into the phenomena such as the expansion due to the increase of the pore pressure and the chemical shrinkage of the anode during the baking process were also gained in this work. These investigations pave the way for modeling the thermo-chemo-poromechanical behaviour of the anode during the baking process.

On the consistency between ionization and trapped runaway electron acceleration in a pulsed discharge

Runaway electrons accelerated in the electric field of a pulsed discharge may substantially change the discharge properties. The existence of this acceleration mechanism is indicated by the x-rays emitted from the discharge and by the increasing propagation velocity of the ionization front. An enhanced non-uniform electric field arises naturally due to the field distortion by the high-density plasma. A simple model is proposed to describe consistently the electron impact ionization, the electric field enhancement by the space charge of the discharge plasma, and the acceleration of runaway electrons to about 100 eV in the enhanced field. Optimal conditions for acceleration, ionization and field enhancement have been found at the plasma density level ∼1015–1016 cm−3 and the energy of hundreds of eV. This energy corresponds to trapped runaway mode of acceleration then the electrons produce maximal ionization instead of continuous acceleration to the anode and x-rays production. Obtained estimations count towards revisiting the role of the runaway electrons in pulsed gas discharge.

Algae-derived hard carbon anodes for Na-ion batteries

In this work, the production of low cost and environment friendly anodes for sodium ion batteries is investigated. Algae are selected as bio-source of non-graphitic Hard Carbon (HC) with open structure acting as intercalation active material for Na ions storage. Chlorella vulgaris algae were pyrolyzed at temperatures comprised between 800 and 1100 °C. The decomposition products have been characterized with Scanning Electrode Microscope (SEM) and X-Ray Diffraction (XRD) analyses and their structure compared to one of the synthetic commercial HC. Thermogravimetric analysis (TGA) allowed to assess the decomposition process throughout the selected temperature scan. The obtained algae-derived HC is tested as anodic material for Na-ion battery, investigating the effect of pyrolysis temperature on the electrochemical behaviour. Their performances are compared with respect to a commercial synthetic HC active material. The results allow to consider algae as an environmentally benign and sustainable high added-value material for the production of HC anodes for Na-ion batteries.Graphic abstract

The Longer Route can be Better: Electrosynthesis in Extended Path Flow Cells.

This personal account provides an overview of work conducted in my research group, and through collaborations with other chemists and engineers, to develop flow electrolysis cells and apply these cells in organic electrosynthesis. First, a brief summary of my training and background in organic synthesis is provided, leading in to the start of flow electrosynthesis in my lab in collaboration with Derek Pletcher. Our work on the development of extended path electrolysis flow reactors is described from a synthetic organic chemist's perspective, including laboratory scale-up to give several moles of an anodic methoxylation product in one day. The importance of cell design is emphasised with regards to achieving good performance in laboratory electrosynthesis with productivities from hundreds of mg h-1 to many g h-1 , at high conversion in a selective fashion. A simple design of recycle flow cell that can be readily constructed in a small University workshop is also discussed, including simple modifications to improve cell performance. Some examples of flow electrosyntheses are provided, including Shono-type oxidation, anodic cleavage of protecting groups, Hofer-Moest reaction of cubane carboxylic acids, oxidative esterification and amidation of aldehydes, and reduction of aryl halides.

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

Modification of biocoke destined for the fabrication of anodes used in primary aluminum production

Calcined petroleum coke, recycled anodes and the coal tar pitch are the raw materials used to manufacture carbon anodes for aluminum production. In order to reduce greenhouse (GHG) emissions from the aluminum industry and to add a value to the residue of wood industry, a small part of the calcined petroleum coke, used for the production of carbon anodes, was replaced with biocoke produced from wood by-products. Since the addition of biocoke deteriorates the properties of carbon anodes, it was modified using an additive in order to assess if the modification can render biocoke more suitable for carbon anode production by modifying the surface chemistry of the biocoke.Three samples of biocoke, unmodified, modified using 3% additive and modified using 4% additive, were produced and studied before and after modification to identify its effect on biocoke properties. First, the chemical characterization was carried out using X-ray photoelectron spectrometry (XPS) to verify whether the functional groups were added to the biocoke surface during the modification. To study the influence of the biocoke modification on the biocoke/pitch interactions, the wettability of the unmodified and modified biocokes by the coal tar pitch, which is used as a binder in anodes, were measured using sessile-drop test. After, the laboratory scale anodes were produced and their green and baked densities, electrical resistivity, air and CO2 reactivities, and bending strength were measured. The results showed that the biocoke modification was effective. A number of new surface chemical groups were added to the biocoke coke surface. This improved the biocoke/pitch wettability, consequently affected the anode properties.

A photo-renewable ZIF-8 photo-electrochemical sensor for the sensitive detection of sulfamethoxazole antibiotic

Electroanalysis is an effective monitoring method for organic pollution in environmental samples. However, chemical fouling with the formation of non-conductive fouled films easily occurs on the surface of the electrode during organic pollution detection that would inactivate the electrode and affect the detecting sensitivity of organic pollution. In this work, we found that zeolitic imidazolate framework-8 (ZIF-8) electrode can achieve effective degradation of non-conductive fouled films under the light illumination during electrochemical detection of some typical organic pollution (sulfamethoxazole (SMX), Bisphenol A (BPA) and diclofenac sodium (DS)). Profiting from the charge transfer capability and photoelectric characteristics, ZIF-8 electrode exhibits a lower detection limitation for organic pollution detection and superior regeneration property. The nice detection and superior regenerated property are mainly due to non-selective superoxide radical (·O2−) and hydroxyl radicals (·OH) mediation produced by ZIF-8 electrode under light illumination that can mineralize anodic fouled products and resume surface reactive sites. Compared with the single electrochemical determination, photo-assisted electroanalysis provides a stable monitoring and a renewable pathway for practical applications.