Electrolysis Conditions Research Articles

Construction of high-rate performance sulfurized Poly(acrylonitrile) nanofibers cathodes for practical lithium–sulfur batteries via tellurium catalytic regulation

The rapid charge-discharge and wide operating temperature range are of great significance to the research of lithium-sulfur batteries. However, the poor electronic and ionic conductivity of sulfurized polyacrylonitrile limits the high-rate and low-temperature performance of lithium-sulfur batteries. In this work, a tellurium-doped sulfurized polyacrylonitrile nanofibers-based cathode material (Te0.02S0.98FPAN) is successfully fabricated by air-blow spinning for lithium-sulfur batteries. It is found that Te0.02S0.98FPAN maintained a high reversible specific capacity of 742 mAh·g−1composites after 200 cycles at a current density of 0.2 C (0.014% decay per cycle), whereas it provides a reversible specific capacity of 641 mAh·g−1composites after 500 cycles even at a large current density of 1.0 C (0.021% decay per cycle), manifesting its excellent high-rate performance. Moreover, Te0.02S0.98FPAN still maintained a high reversible specific discharge capacity of 586 mAh·g−1composites after 100 cycles at 0.2 C at a low temperature of 5.0 °C, confirming its wide operating temperature range. Both the eutectic accelerator (tellurium) and the one-dimensional nanofibrous structure greatly improve the migration rate and electron transport ability of Li+ ions, enhancing reaction kinetics and providing fast and stable migration channels for ions and electrons. Therefore, Te0.02S0.98FPAN has a higher oxidation-reduction reaction rate and less polarization. This study not only provides new ideas for the cathode design of lithium-sulfur batteries with high rate and wide temperature range, but also paves the way for the development of practical lithium-sulfur batteries. In particular, when tested in practical conditions of high areal loading (Te0.02S0.98: 5.0 mg cm−2) and lean electrolyte (E/Te0.02S0.98: 10 μL mg−1), this cathode delivers high reversible capacities of 725 mAh g−1 composite (0.1 C) and 663 mAh g−1 composite (0.2 C), demonstrating its great potential for future application.

Microstructure and Properties of Porous Copper Foils with High Specific Surface Area Prepared by Electrodeposition

The high surface area porous copper foils are synthesized on commercial copper foils by dynamic hydrogen bubble template electrodeposition method. The electrochemical deposition mechanism of porous copper foils and the current density on the structure formation mechanism are explored. The results show that under the conditions of stable electrolyte, electrodeposition time of 20 s, and current density of 2 A·cm−2, the microporous distribution of the deposited layer is uniform and the adhesion between the pore walls is strong. Compared with the planar copper foil, the porous copper foil possesses the “large on top and small on bottom” porous structure, which significantly improves the specific surface area of the copper foil, and the resistance value decreases by 43.1%. The electrochemical test results show that the performance of the porous collector is significantly better than that of the planar collector. Furthermore, the porous copper collector has a lower charge transfer impedance (150 Ω). The results of this paper provide an innovative strategy for the preparation of porous collectors and for solving the problem of lithium metal batteries.

A functional SnS2-engineered separator for durable and practical lithium metal battery

Lithium (Li) metal is one of the most promising anodes for next-generation high-energy-density batteries. However, the practical application of Li metal anodes (LMAs) is hindered by uncontrollable solid electrolyte interphase (SEI) formation and detrimental Li dendrites growth. Herein, a well-designed SnS2 nanoflakes coating is utilized to modify the commercial polypropylene (PP) separator (denoted as SnS2@PP), providing a solution to tackle above issues. Impressively, an artificial SEI consisting of Li2S, Li5Sn2, and Li7Sn2 species with high ionic conductivity and superior Li affinity is generated on the Li surface to regulate homogeneous Li plating/stripping. Consequently, the Li||Li symmetric cells exhibit a stable cycling behavior of over 2700 h at 1 mA cm−2 for 1 mAh cm−2. Remarkably, SnS2@PP enables over 600 cycles at 2 C with a capacity retention of ∼80% in a Li||LiFePO4 coin cell and more than 110 cycles at 0.3 C with a capacity retention of ∼97% in a Li||LiFePO4 pouch cell under high cathode loading (13 mg cm−2), ultrathin Li foil (50 µm), and lean electrolyte (2.8 g Ah−1 after sealed) conditions. This work extends the scalable technology into a platform to control Li deposition and SEI formation toward practical Li metal batteries (LMBs) with ultralong life spans.

Monolithically Integrated BiVO4/Si Tandem Devices Enabling Unbiased Photoelectrochemical Water Splitting

AbstractA photoelectrochemical (PEC) water splitting device based on a dual‐junction monolithic tandem cell that utilizes NiOOH/FeOOH/BiVO4/SnO2/Ta:SnO2 (TTO)/tunnel oxide passivated contact (TOPCon) Si is reported. The PEC device achieves a maximum photocurrent density of 1.4 mA cm−2 (equal to a solar‐to‐hydrogen conversion efficiency of 1.72%) in 1.0 m potassium borate solution (pH 9) when illuminated with air mass 1.5 G simulated solar irradiation, which is the highest value among dual‐junction monolithic photoelectrochemical cells except for III–V materials. The TOPCon Si not only works as an appropriate bottom photoelectrode for subsequent high‐temperature BiVO4 processing but also offers a high photovoltage of 590 mV. Transparent and conductive TTO grown by pulsed laser deposition serves as a recombination layer to achieve effective integration. In addition, the TTO provides chemical and physical protection, allowing the surface of the TOPCon Si to exhibit 24 h of tandem cell stability under weak base electrolyte conditions. The SnO2 hole‐blocking layer inserted between TTO and BiVO4 enhances the charge separation of BiVO4, allowing the device to achieve high efficiency. Artificial leaf‐type monolithic tandem cells consisting of NiFe/BiVO4/SnO2/TTO/TOPCon Si/Ag/Ti/Pt with a solar‐to‐hydrogen efficiency of 0.44% are also demonstrated.

A multifunctional LaFeO3 nanocages modified separator for propelling polysulfides chemisorption and catalytic conversion in Li-S batteries

The sluggish reaction kinetics of sulfur and the shuttle effect of intermediate polysulfides are the thorny issues for the commercialization of Li-S batteries. Commercial polypropylene separators cannot prevent the shuttling of polysulfides due to their large porosity. Therefore, the development of a novel type of separator can efficiently prohibit the transmission of polysulfides, will be beneficial to the practical application of Li-S batteries. Herein, we report a commercial membrane modified with perovskite-type LaFeO3 nanocages to block the transportation of polysulfides. Researches show that the modified multifunctional separators can not only effectively inhibit the shuttle of polysulfides, but also accelerate the reaction kinetics between S and Li2S. The electrochemical performance is greatly improved, which can be mirrored in the rate performance: 689.3 mA h g−1at 4C, and cycling performance with the capacity decay rate of only 0.0585% per cycle for 1000 cycles at 1C. More significantly, the considerable electrochemical performance is still hold under the harsh condition of lean electrolyte.

Dried figs like nitrogen-doped graphene oxide anchored cobalt-doped Fe3O4 nanoparticle as sulfur host for high performance Li-S battery

Lithium-sulfur batteries (LSBs) represent a prospective energy storage device because of their low cost and high theoretical energy density. However, the performance of LSBs was largely constrained by the kinetics of polysulfides (LiPSs) conversion and shuttle effect. Thus, a metal-doped metal oxide is proposed as an efficient adsorbent and catalyst for LiPSs. We designed cobalt-doped Fe3O4 nano-catalysts which was in situ grown on the N-doped graphene conductive network as a multifunctional sulfur host. Evidenced by experimental characterization, it is demonstrated that due to the appropriate doping amount (EGO/Co-Fe3O4 (700)), the host exhibits efficient adsorption and rapid catalytic conversion of LiPSs. Compared with the undoped Co catalyst (S@EGO/Fe3O4), The S@EGO/Co-Fe3O4 (700) electrode possesses high initial discharge specific capacity (1488.4 mAh/g, 0.2 C), and superior cycle stability (900.8 mAh/g after 100 cycles). Impressive performances are also attained at lean electrolyte conditions (electrolyte-to-sulfur (E/S) ratio ∼ 7 μL mg−1).

Electrolytes with moderate lithium polysulfide solubility for high-performance long-calendar-life lithium–sulfur batteries

Lithium-sulfur (Li-S) batteries with high energy density and low cost are promising for next-generation energy storage. However, their cycling stability is plagued by the high solubility of lithium polysulfide (LiPS) intermediates, causing fast capacity decay and severe self-discharge. Exploring electrolytes with low LiPS solubility has shown promising results toward addressing these challenges. However, here, we report that electrolytes with moderate LiPS solubility are more effective for simultaneously limiting the shuttling effect and achieving good Li-S reaction kinetics. We explored a range of solubility from 37 to 1,100 mM (based on S atom, [S]) and found that a moderate solubility from 50 to 200 mM [S] performed the best. Using a series of electrolyte solvents with various degrees of fluorination, we formulated the Single-Solvent, Single-Salt, Standard Salt concentration with Moderate LiPSs solubility Electrolytes (termed S6MILE) for Li-S batteries. Among the designed electrolytes, Li-S cells using fluorinated-1,2-diethoxyethane S6MILE (F4DEE-S6MILE) showed the highest capacity of 1,160 mAh g-1 at 0.05 C at room temperature. At 60 °C, fluorinated-1,4-dimethoxybutane S6MILE (F4DMB-S6MILE) gave the highest capacity of 1,526 mAh g-1 at 0.05 C and an average CE of 99.89% for 150 cycles at 0.2 C under lean electrolyte conditions. This is a fivefold increase in cycle life compared with other conventional ether-based electrolytes. Moreover, we observed a long calendar aging life, with a capacity increase/recovery of 4.3% after resting for 30 d using F4DMB-S6MILE. Furthermore, the correlation between LiPS solubility, degree of fluorination of the electrolyte solvent, and battery performance was systematically investigated.

Selective two-electron electrocatalytic conversion of 5-Hydroxymethylfurfural boosting hydrogen production under neutral condition over Co(OH)2-CeO2 catalyst

The coupling of electrocatalytic oxidation of biomass derivatives with hydrogen evolution reaction (HER) is a promising strategy to promote hydrogen production, but it is extremely challenging to control the mild electrocatalytic conversion of biomass to high value-added chemicals simultaneously. A Co(OH)2-CeO2 self-supported catalyst is constructed and used as anode for selective electrocatalytic conversion of biomass derivative 5-hydroxymethylfurfural (HMF) coupled with HER in two-chamber electrolysis system. The adjusting of pH and potential regulates the oxidation ability of hydroxyl and aldehyde groups, achieving selective two-electron electrocatalytic conversion of HMF to 2-furancarboxylic acid (HMFCA) with a selectivity of 89.4%. In situ Raman spectroscopy reveals that the evolution of Co multivalent active species at different electrolysis conditions is key to the selective oxidation of HMF. In addition, the hydrogen production coupled with selective electrocatalytic conversion of HMF is 4.1 times that of the water splitting system, revealing its potential in developing clean energy.

Heterogeneous bimetallic oxysulfide nanostructure (Ni-Co) as hybrid bifunctional electrocatalyst for sustainable overall alkaline simulated seawater splitting

The design and development of high performance non-precious bifunctional electrocatalytic activity for oxygen/hydrogen evolution reaction (OER/HER) remains a significant challenge in overall seawater splitting process. Herein, we report the Co3S4/Co3O4 hybrid nanostructures catalyst with duel functions is successfully in-situ synthesized through self-templating strategy, whereas, Ninanostructure 3S2/NiO are grown on Ni foam using a facile hydrothermal reaction and post thermal annealing process. The designed self-standing Co3O4(Co3S4)/NiO(Ni3S2)/NF nanostructure (denoted as Co-Ni-S/NF) as a self-standing hybrid electrode demonstrates an excellent bifunctional electrocatalytic activity for OER and HER process in alkaline freshwater/alkaline simulated seawater as electrolyte. Taking advantage of the bimetallic synergistic effect and formation of an efficient interface layer of Ni3S2/NiO in a unique nanostructure, the resultant bifunctional electrocatalytic performance of Co-Ni-S/NF electrode for OER & HER processes are highly performed in both electrolyte conditions. Specifically, Co-Ni-S/NF hybrid electrode requires lower overpotentials of 270 mV (at 20 mV cm−2), 310 mV (at 50 mV cm−2) for OER and lower overpotentials of 239 mV (at 20 mV cm−2), 291 mV (at 50 mV cm−2) for HER in alkaline simulated seawater condition. For two-electrode based electrolyzer analyses, Co-Ni-S/NF electrode based electrolyzer demonstrates low cell voltage of 1.67 V to attain a current density of 10 mA cm−2 with stable activity of overall alkaline simulated seawater splitting process whereas hybrid electrode used as anode and cathode. Therefore, the proposed interface engineering strategy and rationally constructing electrocatalyst nanostructure via a self-templating route could be a promising opportunity to develop an active duel functional catalyst for direct seawater splitting applications.

Lithium Tritelluride as an Electrolyte Additive for Stabilizing Lithium Deposition and Enhancing Sulfur Utilization in Anode‐Free Lithium–Sulfur Batteries

AbstractDespite the potential to become the next‐generation energy storage technology, practical lithium–sulfur (Li–S) batteries are still plagued by the poor cyclability of the lithium‐metal anode and sluggish conversion kinetics of S species. In this study, lithium tritelluride (LiTe3), synthesized with a simple one‐step process, is introduced as a novel electrolyte additive for Li–S batteries. LiTe3 quickly reacts with lithium polysulfides and functions as a redox mediator to greatly improve the cathode kinetics and the utilization of active materials in the cathode. Moreover, the formation of a Li2TeS3/Li2Te‐enriched interphase layer on the anode surface enhances ionic transport and stabilizes Li deposition. By regulating the chemistry on both the anode and cathode sides, this additive enables a stable operation of anode‐free Li–S batteries with only 0.1 m concentration in conventional ether‐based electrolytes. The cell with the LiTe3 additive retains 71% of the initial capacity after 100 cycles, while the control cell retains only 23%. More importantly, with high utilization of Te, the additive enables significantly better cyclability of anode‐free pouch full‐cells under lean electrolyte conditions.

Holistic evaluation of limited voltage windows paired with artificial solid-electrolyte interphase under lean electrolyte conditions of Li[sbnd]S batteries

Lean electrolyte conditions are detrimental to the cycling performances of LiS batteries, so electrolyte-to‑sulfur (E/S) ratios are often much higher than 15 μL mg−1. However, the energy density of such flooded cells is far inferior to those of commercial Li-ion batteries despite 8–10 times higher specific capacity of sulfur cathodes compared to the metal oxide-based cathodes. Here we propose to limit the voltage window for mitigating the detrimental effect by holistically evaluating the effects of the upper and lower cycling voltage windows to unveil the major causes of the unstable cycling behaviors. With a high total sulfur loading of 7 mg cm−2, our approach utilizing a low depth of charge/discharge (1.95–2.45 V) has enabled long and stable cycling (> 400 cycles with capacity retention of 80 %). It has mitigated irreversible polysulfide passivation on the lithium metal anode when paired with an artificial solid-electrolyte interphase (A-SEI) layer, which has been a critical problem called the shuttle effect. Electrolyte degradation such as lithium salt decomposition was suppressed by cutting off the upper voltage window. Outstanding capacity retention larger than 90 % for >180 cycles was demonstrated under a lean electrolyte condition (E/S ≈ 5 μL mg−1) with the superb actual cell-level energy density of 569 Wh L−1, which is better or at least comparable to those of commercial Li-ion batteries. More importantly, despite the reduction of the specific capacity due to the reduced voltage window, both the cumulative volumetric and gravimetric energy densities are superior to those in the literature, suggesting an effective method of extending the cycling life. Strikingly, based on the actual energy density, the material cost of our cell is considerably low (∼$29 per kWh), which is about half the cost of the popular Li-ion batteries.

Uncovering the solid-phase conversion mechanism via a new range of organosulfur polymer composite cathodes for lithium-sulfur batteries

The sulfur cathodes operating via solid phase conversion of sulfur have natural advantages in suppressing polysulfide dissolution and lowering the electrolyte dosage, and thus realizing significant improvements in both cycle life and energy density. To realize an ideal solid-phase conversion of sulfur, a deep understanding of the regulation path of reaction mechanism and a corresponding intentional material and/or cathode design are highly essential. Herein, via covalently fixing of sulfur onto the triallyl isocyanurate, a series of S-triallyl isocyanurate organosulfur polymer composites (STIs) are developed. Relationship between the structure and the electrochemical conversion behavior of STIs is systematically investigated. It is found that the structure of STIs varies with the synthetic temperature, and correspondingly the electrochemical redox of sulfur can be controlled from conventional “solid–liquid–solid” conversion to the “solid–solid” one. Among the STI series, the STI-5 composite realizes an ideal solid-phase conversion and demonstrates great potential for building a Li–S battery with high-energy density and long-cycle-life: it realizes stable cycling over 1000 cycles in carbonate electrolyte, with a degradation rate of 0.053% per cycle; the corresponding pouch cell shows almost no capacity decay for 125 cycles under the conditions of high sulfur loading (4.5 mg cm−2) and lean electrolyte (8 μL mgs−1). In addition, the tailoring strategy of STI can also apply to other precursors with allyl functional groups to develop new organosulfur polymers for “solid–solid” sulfur cathodes. The vulcanized triallyl phosphate (STP) and triallylamine (STA) both show great lithium storage potential. This strategy successfully develops a new family of organosulfur polymers as cathodes for Li–S batteries via solid-phase conversion of sulfur, and brings insights to the mechanism study in Li–S batteries.

Silicon electrodeposition from the KF-KCl-K<sub>2</sub>SiF<sub>6</sub> and KF-KCl-KI-K<sub>2</sub>SiF<sub>6</sub> melts

Silicon and silicon-based materials find extensive applications in metallurgy, microelectronics, and other emerging industries. The field of use of synthesized silicon varies based on its morphology and purity. This study employs voltammetry, galvanostatic electrolysis, and scanning electron microscopy to examine the impact of KI surfactant (in mol %) to 66.5KF–33.3KCl–0.23K2SiF6 melt at 750°C on the electrowinning kinetics of silicon ions and the morphology of silicon deposits formed on a glassy carbon electrode. The findings demonstrate that the addition of potassium iodide to the KF–KCl–K2SiF6 melt at a concentration of 2 mol % induces changes in interfacial tension at the boundary between the glassy carbon, melt, and atmosphere. Consequently, the wetting of the glassy carbon with the melt decreases, leading to a reduction in the actual working surface area and, consequently, a decrease in cathode current while maintaining current density. Taking into account this effect and employing an algebraic estimation of the influence of the melt meniscus shape, it is postulated that the addition of KI does not significantly affect the kinetics of the cathode process. Nevertheless, the impact of KI addition on the morphology of electrodeposited silicon is mentioned. During the electrolysis of the KF–KCl–K2SiF6 melt, fibrous silicon deposits with arbitrary shapes are formed on the glassy carbon electrode, whereas the addition of 2 and 4 mol % of potassium iodide to the melt leads to the agglomeration and smoothing of silicon deposits under the same electrolysis conditions (cathode current density: 0.02 A/cm2, electrolysis duration: 2 h). The obtained results indicate the potential to manipulate the morphology of electrodeposited silicon for specific applications in various fields.

Hidden Macroscopic Degradation Behavior in Rechargeable Lithium–Oxygen Batteries under Lean Electrolyte and High Areal Capacity Conditions

As lithium–oxygen batteries (LOBs) possess extremely high theoretical energy densities that exceed those of lithium-ion batteries, they are regarded as promising candidates for portable energy applications, including as power sources for next-generation electrical devices. However, physical degradation factors affecting the prolonged cycle of the LOBs, such as electrode volume changes and electrolyte displacement, have been rarely explored thus far, owing to the technical difficulty of applying non-destructive analytical methods to LOBs during cycling. In the present study, we employed ex situ X-ray computerized tomography (XCT), in situ internal pressure monitoring, and in situ confocal microscopy to study the physical states of the electrodes and the electrolyte in high energy density LOBs. The analysis results reveal that large irreversible volume changes occurred in both the positive electrode and the negative electrode of the LOB cells. Furthermore, it was also confirmed that the electrolyte was displaced from the pores of the positive electrode associated with the formation of Li2O2 in these pores during the discharge process. As these results present new fundamental insights into the physical behavior of LOBs during cycling conditions, the methodologies demonstrated here are therefore effective means to gain a new understanding of complex physical processes previously unexamined in LOBs, which shed light on the future design strategies of LOBs with high energy density and long cycle life.

Conductive vanadium-based metal-organic framework nanosheets membranes as polysulfide inhibitors for lithium-sulfur batteries

The polysulfide shuttle is regarded as the most critical challenge that hinders the commercial process of lithium-sulfur batteries (LSBs). Herein, a vanadium-based MIL-47 nanosheets membrane is fabricated on carbon nanotube film for this trouble, which serves as a versatile interlayer material in LSBs. With a good electrolyte wettability, thin thickness and appropriate pore diameter, MIL-47 nanosheets membrane is capable of efficaciously blocking polysulfides and enabling the fast transport of Li ions via the selectively sieving effect. Furthermore, the excellent conductivity and fully exposed catalytic metal centers contribute to enhance the reaction kinetics and sulfur utilization. Therefore, this MOF-based interlayer provides a wonderful capacity of 1044.6 mAh g−1 and a durable cyclic performance with a numbered decay of 0.03 % per cycle for 1000 cycles at 1 C. Even under harsh conditions of high sulfur loading and lean electrolyte, excellent cycle and rate performances are still acquired. This work boosts the development of multi-functional materials in LSBs.

Selective Electrocatalytic CO2 Reduction into CO Using Au-Coated Dendritic Silica Nanoparticle Arrays

Highly selective electrocatalytic CO2 reduction for CO production has attracted tremendous attention for achieving the forthcoming goals of carbon neutrality and widespread industrial utilization and recycling of carbon. Among various approaches, the structural control of the catalyst is particularly interesting because of the facile control of CO2 reduction conditions, such as reaction media and reaction pathways. Thus far, a wide range of nanostructured catalysts, including Au needle tips, Au nanowires, and Au wrinkles, have been used for the enhancement of the selectivity of CO production. In this study, an electrocatalyst with a hierarchical nanostructure for the highly selective production of CO is reported. This hierarchical structure is fabricated by the deposition of Au via e-beam evaporation on a dendritic fibrous nanosilica (KCC-1) template, which is a spherical silica particle consisting of uniformly distributed center-radial fibers. The conversion efficiency of this catalyst is strongly affected by the thickness of the Au deposited on the KCC-1 template, and the highest CO selectivity of ∼98% (at −0.5 V vs. RHE) is obtained at an optimum Au thickness of 50 nm. According to the CO2 electrocatalytic reduction results obtained from KCC-1 with dendritic fibers and a conventional spherical particle without the fibers under various electrolyte conditions, such selectivity enhancement of Au on the KCC-1 template is attributed to the increase in the local pH near the hierarchical catalyst surface. This work provides potential promising templates that exhibit a unique nanostructure for efficient electrocatalysis.

Photo- or Electrochemical Cyclization of Dienes with Diselenides to Access Seleno-Benzo[b]azepines.

A cascade selenylation/cyclization of dienes with diselenides has been realized under visible-light irradiation or electrolysis conditions. Employing O2 or electricity as a "green" oxidant, this protocol provides a green and efficient method for an array of biologically important seleno-benzo[b]azepine derivatives in moderate to good yields. The direct sunlight irradiation and gram-scale reaction render the approach practical and attractive.

Electrochemical Activity and Stability of Pure Gadolinium Doped Ceria as Fuel Electrode in Solid Oxide Electrolysis Cells

The utilization of novel fuel electrode materials could be a valid solution to improve the durability of solid oxide electrolysis cells and the path way for worldwide commercialization. Especially, Ni-free fuel electrodes are promising to eliminate Ni migration as an important degradation mechanism. Gadolinium doped ceria (GDC) is an interesting material due to its good stability towards carbon deposition and the possibility to host electrocatalysis in electrolysis conditions. The present study aims to investigate the performance, electrochemical processes and long-term stability of pure GDC fuel electrode single cells. The results show a lower degradation rate in comparison to similar produced Ni-GDC single cells in steam electrolysis conditions and around 70 % of its performance. Furthermore, the charge transfer in the GDC fuel electrode is identified as the reaction rate-determining process in the GDC fuel electrode single cells.

Comparison of the Electrochemical and Degradation Behaviour of Ni-YSZ and Ni-GDC Electrodes Under Steam, Co- and CO2 Electrolysis

This present study aims to investigate and compare the long-term stability of Ni-GDC and Ni-YSZ under three different electrolysis modes; steam electrolysis, co-electrolysis and CO2 electrolysis. Firstly, electrolyte-supported single cells of Ni-GDC (NiO-GDC//8YSZ//GDC//LSCF) and Ni-YSZ (NiO-GDC//8YSZ//GDC//LSCF) were fabricated and investigated using electrochemical impedance spectroscopy (EIS). Furthermore, the impedance data were also recorded under polarization (0.7 to 1.4V) as well as at OCV. Finally, stability tests of the single cells were carried out under steam (H2O:H2, 50:50), co- (H2O:CO2:CO, 40:40:20) and CO2 electrolysis (CO2:CO, 80:20) conditions at 900 °C with -0.5 A/cm2 current density. The results reveal that Ni-GDC exhibits higher current density and lower polarization resistance (Rp) than Ni-YSZ in all the electrolysis modes. Furthermore, the Ni-GDC cells show a lower degradation rate than Ni-YSZ. However, Ni migration and agglomeration were observed in both electrodes. The detailed electrochemical and microstructural properties of the operated cells will be presented and discussed.

Evaluation and Upscaling of Impregnated La0.20Sr0.25Ca0.45TiO3 Fuel Electrodes for Solid Oxide Electrolysis Cells Under H2O, CO2 and Co-Electrolysis Conditions

Recent research into Rh and Ce0.80Gd0.20O1.90-impregnated La0.20Sr0.25Ca0.45TiO3 fuel electrodes for solid oxide fuel cells has demonstrated the high-stability of these material sets to a variety of harsh operating conditions at small scales (button cells with 1 cm2 active area), as well as full commercial scales (100 cm2 cells) in short stacks (5 cells) and full micro-combined heat and power systems (60 cells). In this work, the authors present a comprehensive evaluation of the ability of these novel titanate-based materials to function as fuel electrodes in solid oxide electrolysis cells (SOECs). Short-term and durability testing of button cell scale SOECs, under CO2 and steam electrolysis conditions, highlighted the limited stability of lanthanum strontium manganite-based air electrodes with lanthanum strontium cobaltite ferrite-based air electrodes offering improved degradation. Upscaling of this optimized cell chemistry to a 16 cm2 active area SOEC and testing under CO2, CO2/steam and steam electrolysis conditions demonstrated encouraging performance over a period of ~600 hours.