Search

Hydrogen has been widely recognised as a key resource in transitioning towards a sustainable and decarbonised energy future. Of the available hydrogen production processes, solid oxide electrolysis is a promising way to produce green hydrogen via high temperature electrolysis. The high conversion efficiencies of solid oxide electrolysis systems combined with the ability to integrate this technology with downstream chemical syntheses plants make them very attractive compared to other electrolysis technologies. However, solid oxide electrolysis, to date is the least developed electrolysis technology from the point of view of large-scale commercialisation. In recent years, significant research on fabrication and testing of individual solid oxide electrolyser (SOE) cells has been reported which has led to a multi-fold improvement in cell performance. Improvements on a cell level, though do not directly translate to improvements on a stack and system-level scale. Scaling-up solid oxide electrolysers for higher hydrogen production rates is challenging. This review presents an overview of the experimental and modelling investigations of the stack and system-scale SOE technology. The current commercial status of the SOE systems is highlighted and further improvements needed for successful near and long-term commercialisation of the technology are discussed. [Display omitted] • Solid oxide electrolyser systems are reviewed, with a focus on stacks and modules. • Experimental studies on solid oxide stack testing are discussed. • Numerical and system-level modelling-based studies are reviewed in depth. • Current status of commercial solid oxide electrolyser systems is highlighted. • Challenges and future outlook for the technology are discussed. [ABSTRACT FROM AUTHOR]

The major technologies being considered for the green hydrogen production are polymer electrolyte membrane (PEM) and solid oxide electrolysis (SOE). While PEM electrolysis technology is nearing commercialisation with units now being globally installed at tens of MW scale, SOE technology is still under development with units available only at 100s of kW scale and at much higher costs per kW. SOE due to its high operating temperatures (close to 800 °C) has the potential to reduce the electric energy input by up to 30% for the hydrogen production per tonne by using the low-cost thermal energy input available from the industrial or downstream synthesis processes. The SOE cathode, where steam electrolysis occurs, plays a crucial role in dictating the cell voltage losses and the stability of the cell operation that eventually has a large impact on the SOE efficiency and lifetime. The current state-of-the-art cathode materials based on Ni-YSZ pose many challenges. There is, therefore, a global effort to find alternative cathode materials suitable for steam electrolysis in SOE. This review critically reviews novel nanoengineered cathode materials and points to the fact that such materials synthesized using infiltration and exsolution techniques, in combination with advanced materials characterisation like high-temperature scanning probe microscopy and in situ Raman spectroscopy can be a right approach to find the suitable cathode materials for steam electrolysis in SOE. This, however, may need to be combined with a techno-economic analysis to provide the technical and economic viability of these materials for the SOE commercialisation. [Display omitted] • High temperature steam electrolysis critically reviewed, focussing on cathode materials. • Conventional and alternative cathode materials briefed, and their challenges discussed. • Novel heterostructured materials and their drawbacks discussed in-depth. • Scope of further research around novel materials highlighted at the end. [ABSTRACT FROM AUTHOR]

In the quest for long-lasting energy alternatives, solid oxide electrolysers have become a crucial technology in facilitating the transformation of CO 2 toward fuels and valuable chemicals. This study proposes a unique method for the catalytic reduction of carbon dioxide at the cathode using porous CeO 2 single-crystal electrodes in a solid oxide electrolyser, utilizing temperatures from an industrial waste heat stream. The fluxes and chemical states of oxygen-containing species evolved from the cathode were identified and designed, and the catalytic process of CO 2 reduction to CO was effectively regulated by the oxygen-containing species (lattice oxygen, oxygen vacancies and adsorbed oxygen). The results show that the CO yield can reach 6.05 mL min−1 cm−1 with porous (111) CeO 2 single crystal as the cathode at 850 °C and 1.8 V. The solid oxide electrolyser exhibits remarkable stability even after 100 h of continuous operation. We have prepared porous CeO 2 single crystals with abundant oxygen vacancies, which can capture large amounts of CO 2 for full electrolytic reduction and exhibit excellent electrochemical properties and stability. [Display omitted] • Porous CeO 2 single crystals with abundant oxygen vacancies are prepared. • The porous CeO 2 single crystal pore model is reconstructed in three dimensions. • The presence of oxygen vacancies facilitates CO 2 reduction. • Porous CeO 2 single crystals exhibit excellent and stable electrocatalytic properties. [ABSTRACT FROM AUTHOR]

Increasing densities of reaction sites for gaseous reactants in solid oxide electrochemical reactors (SOERs), is a key strategy for achieving enhanced performance in either fuel cell or electrolysis modes. Fabrication of 3D structured components in SOERs can enhance those densities of reaction sites, which is achieved by 3D inkjet printing with high reproducibility, having developed inks with appropriate properties. First, the effects of pillar geometries on SOER performances are predicted through numerical simulations, enabling subsequent 3D printing to focus on the more effective geometries. Herein, the study reports the results of experimental validation of those predictions by evaluating the electrochemical performances of cells with various heights of 3D inkjet-printed Ni(O)- yttria stabilized zirconia (YSZ) pillars and YSZ pillars. Those measurements prove that increasing pillar heights generally increases SOER peak power densities in fuel cell mode and increased current densities at the thermoneutral potential (1.285 V) in steam electrolysis mode, as predicted by simulations. With increasing pillar heights, more limitations in performance enhancement are found with YSZ electrolyte pillars than with Ni-YSZ pillars, again as predicted by simulations. The subsequent microstructural analysis of Ni-YSZ pillars proves the suitability of the Ni(O)-YSZ composite particle ink formulation and the reliability of 3D printing., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

Hydrogen is currently being promoted because of its advantages as an energy vector, its potential to decarbonise the economy, and strategical implications in terms of energy security. Hydrogen from high-temperature electrolysis coupled with concentrated solar power (CSP) is especially interesting since it enhances the last two aspects and could benefit from significant technological progress in the coming years. However, there is a lack of studies assessing its future environmental performance. This work fills this gap by carrying out a prospective life cycle assessment based on the expected values of key performance parameters in 2030. The results show that parabolic trough CSP coupled with a solid oxide electrolyser is a promising solution under environmental aspects. It leads to a prospective hydrogen carbon footprint (1.85 kg CO 2 eq/kg H 2) which could be classified as low-carbon according to current standards. The benchmarking study for the year 2030 shows that the assessed system significantly decreases the hydrogen carbon footprint compared to future hydrogen from steam methane reforming (81% reduction) and grid electrolysis (51%), even under a considerable penetration of renewable energy sources. • Life-cycle profile of renewable hydrogen from solid oxide electrolysis in 2030 is assessed. • A simulation model with concentrated solar power integration is built for data supply. • Prospective carbon footprint shows that hydrogen from this system qualifies as green. • In solar-only mode, solar infrastructure becomes an environmental hotspot. • Solar plant scale arises as a key factor affecting the life-cycle profile of hydrogen. [ABSTRACT FROM AUTHOR]

The current study develops a hydrogen map concept where renewable energy sources are considered for green hydrogen production and specifically investigates the solar energy-based hydrogen production potential in Turkey. For all cities in the country, the available onshore and offshore potentials for solar energy are considered for green hydrogen production. The vacant areas are calculated after deducting the occupied areas based on the available governmental data. Abundant solar energy as a key renewable energy source is exploited by photovoltaic cells. To obtain the hydrogen generation potential, monocrystalline and polycrystalline type solar cells are considered, and the generated renewable electricity is directed to electrolysers. For this purpose, alkaline, proton exchange membrane (PEM), and solid oxide electrolysers (SOEs) are considered to obtain the green hydrogen. The total hydrogen production potential for Turkey is estimated to be between 415.48 and 427.22 Million tons (Mt) depending on the type of electrolyser. The results show that Erzurum, Konya, Sivas, and Van are found to be the highest hydrogen production potentials. The main idea is to prepare hydrogen map in detail for each city in Turkey, based on the solar energy potential. This, in turn, can be considered in the context of the current policies of the local communities and policy-makers to supply the required energy of each country. • To prepare hydrogen maps based on available solar energy potential for a country. • To assess the green hydrogen production potential of cities from their available extra electric energy. • To show the hydrogen production difference among three commercially available electrolysers. • To compare onshore and offshore hydrogen production potential of different regions of a Turkey. [ABSTRACT FROM AUTHOR]

Increasing densities of (electrode–electrolyte-pore) triple phase boundaries (TPBs) / reaction sites enhance performances of solid oxide electrochemical reactors (SOERs) in both fuel cell (SOFC) and electrolyser (SOE) modes. Inkjet 3D printing is capable of construction of ceramic microstructures on support layers, enabling fabrication of SOERs with enhanced active area to geometric area ratios, thereby up-scaling effective areas / TBP lengths per unit volume.A Ni(O)-YSZ functional layer was designed and 3D inkjet printed with a surface of circular pillars, a facile geometry for printing that increased the interfacial to geometric area ratio. Deposition of further functional layers and sintering resulted in fully fabricated reactors with structures: H2O-H2 | Ni(O)-YSZ support | Ni(O)-YSZ pillars | YSZ | YSZ-LSM | O2, Air. The corresponding planar structured cell also was fabricated with the same components, for comparison of its electrochemical performance with that of the pillar-structured cell. The latter exhibited performance enhancement over its planar counterpart by factors of ca. 1.5 in fuel cell mode, ca. 3 in steam electrolysis mode, and ca. 4–5 in CO2 electrolysis mode, thereby demonstrating the potential of geometric structuring of electrode | electrolyte interfaces by 3D printing for developing higher performance SOERs.

Symmetrical solid oxide cells (s-SOC) present several advantages compared to typical configuration, as a reduction of sintering steps or a better thermomechanical compatibility between the electrodes and the electrolyte. Different mixed ionic-electronic conductors (MIEC) have been reported as suitable candidates for symmetrical configuration, allowing operations under steam electrolysis (SOEC) or co-electrolysis (co-SOEC) without the use of reducing safe gas (typically employed in SoA nickel based cells). In the present study, Sr 2 Fe 1.5 Mo 0.5 O 6−δ (SFM) electrodes are deposited on both sides of YbScSZ tapes previously coated with a Ce 1-x Gd x O 1.9 (GDC) barrier layer grown by PLD. Electrode sintering temperature is optimized and fixed at 1200 °C by means of electrochemical impedance spectroscopy (EIS) measurements in symmetrical atmosphere. The cell is then characterized at 900 °C in SOEC and co-SOEC modes without the use of any safe gas obtaining high current densities of 1.4 and 1.1 A cm−2 at 1.3 V respectively. Short-term reversibility is finally proven by switching the gas atmosphere between the cathode and anode sides while keeping the electrolysis conditions. Similar performances are obtained in both configurations. • Symmetrical SOC made with SFM deposited on YbScSZ electrolytes tapes. • Improved GDC PLD barrier layer. • No need of safe gas at the fuel electrode. • High performance of symmetric cells in SOEC and co-SOEC. • Cell reversibility proven by exchanging gas atmosphere between anode and cathode. [ABSTRACT FROM AUTHOR]

Abstract A solid oxide electrolysis cell (SOEC) powered by a renewable source can convert CO 2 into carbon monoxide, which is a valuable feedstock for a range of fuels and chemical processes. The cathode material of the SOEC is required to possess sufficient catalytic activity for CO 2 reduction, and also sustain the thermal and electrical load cycling to which the SOEC would be subjected when coupled with an intermittent renewable source without an auxiliary electricity or thermal storage system. The operating conditions can become even more challenging if solar or waste heat from exothermic downstream industrial processes is to be embedded in the process. In this study, we evaluated a mixed ionic–electronic conducting composite (La 0·80 Sr 0.20 Sc 0.05 Mn 0·95 O 3-δ –Gd 0.20 Ce 0·80 O 1.95) material as an SOEC cathode. Along with initial electrochemical performance, we investigated the cell's response to accelerated ageing tests, including electrical load cycling and extreme thermal cycling. Factors leading to performance degradation were studied by electrochemical impedance spectroscopy and structural characterisation of the cathode before and after the test. Thermal cycling resulted in more pronounced effect on the cell degradation rate as compared to electrical load cycling. Graphical abstract Image 1 Highlights • La 0·80 Sr 0.20 Sc 0.05 Mn 0·95 O 3-δ -Gd 0.20 Ce 0·80 O 1.95 cathode is tested for CO 2 electrolysis. • Solid oxide electrolyser (SOE) evaluated under variable electrical load and thermal conditions. • Thermal cycling caused more significant degradation as compared to load cycling. • Cathode cracking and current collector coarsening identified as major causes of cell degradation. • Integration of SOEs with thermal storage systems is suggested while coupling with renewable source. [ABSTRACT FROM AUTHOR]

The conversion of CO 2 into commodity chemicals and liquid fuels through the integration of renewable energy with electrochemical processes is one of the fast-emerging areas of research in energy space. High temperature electrolysis of CO 2 in solid oxide electrolysis (SOE) cells is one of the most efficient processes for CO 2 to chemical conversion as these reactors can utilize both heat as well as electrical energy. One of the key components that requires further development is the cathode (CO 2 reduction electrode). The traditional Ni based cathodes are prone to rapid degradation under cyclic loading conditions and also require the additional supply of a reducing gas such as hydrogen for maintaining Ni in the metallic state at operating temperatures. In this work, we have proposed and investigated a ceramic composite of nominally A-site deficient (La 0.80 Sr 0.20 ) 0.95 MnO 3-x (LSM) and Gd 0.20 Ce 0.80 O 1.95 (GDC) as SOE cathode using scalable electrolyte supported tube cells. The cells were continuously operated for about 200 h with about 95% Faradaic efficiency. It was observed that LSM–GDC composite cathode was better not only in terms of electrochemical performance, but was also significantly more stable than LSM alone during the CO 2 electrolysis process. The slight degradation (0.18 mA cm −2 per h) in the current density was attributed to the electrode coarsening, and the formation of SrCO 3 phase possibly reducing electrocatalytically active sites. Based upon the electrochemical performance and stability data, LSM-GDC composite appears to be promising material for application as SOE cathode. [ABSTRACT FROM AUTHOR]

A novel integrated renewable-based energy system for production of synthetic diesel is proposed and simulated in this study. This system merges solid oxide electrolyser (SOE), entrained gasification (EG) and Fischer-Tropsch (FT) technologies. Two case scenarios are considered here. In the first case, the electrolyser unite produce syngas through co-electrolysis of steam and carbon dioxide, while in the second case only steam is electrolyzed. The effects of SOEC and EG operating pressure and temperatures on the system performance in each case are investigated and compared. It is shown that the operating condition of electrolyser subsystem has a more considerable effect on the performance of the integrated system as compared to the gasification subsystem. Also waste heat recovery results in about 43 and 2 percentage point increase in energy and exergy efficiency, respectively. It is also shown that internal recovering of oxygen has the best effect on the system performance. [ABSTRACT FROM AUTHOR]

Solid oxide electrolysis cells with La 0·75 Sr 0·25 Cr 0·5 Mn 0·5 O 3-δ (LSCM) cathode can electrolyze CO 2 to generate chemical fuels. Nevertheless, the cathode performance is limited by its electrocatalytic activity. In this work, metal nanoparticles including Ni, Cu and NiCu metals are successfully impregnated in LSCM electrode to improve its activity. XRD, XPS, SEM and TEM together confirm the metal nanocatalysts are homogeneously distributed on LSCM backbone and therefore create active electrochemical interface for CO 2 splitting. Electrical properties of LSCM with impregnated metal nanoparticles are investigated and correlated to electrode performances. Electrochemical measurements show that the NiCu-LSCM demonstrates the optimum performance without degradation after operation for ∼100 h and ∼10 redox cycles. It is believed that the enhanced performance of CO 2 electrolysis may be attributed to the synergetic effect of metal nanocatalyst and LSCM ceramic electrode. [ABSTRACT FROM AUTHOR]

Ammonia is one of the most produced chemicals worldwide and is currently synthesized using nitrogen separated from air and hydrogen from natural gas reforming with consequent high consumption of fossil fuel and high emission of CO 2 . A renewable path for ammonia production is desirable considering the potential development of ammonia as energy carrier. This study reports design and analysis of an innovative system for the production of green ammonia using electricity from renewable energy sources. This concept couples Solid Oxide Electrolysis (SOE), for the production of hydrogen, with an improved Haber Bosch Reactor (HBR), for ammonia synthesis. An air separator is also introduced to supply pure nitrogen. SOE operates with extremely high efficiency recovering high temperature heat from the Haber-Bosch reactor. Aspen was used to develop a model to study the performance of the plant. Both the SOE and the HBR operate at 650 °C. Ammonia production with zero emission of CO 2 can be obtained with a reduction of 40% of power input compared to equivalent plants. [ABSTRACT FROM AUTHOR]

A pressurized solid oxide electrolyser (SOE) system for syngas production is analyzed. The system is modeled and analyzed considering energy and exergy aspects. The main consideration is to quantify the effect of operating pressure on the system performance when syngas is used for synthetic diesel production. At elevated pressures methanation reaction within the electrolyser causes internal production of methane from syngas. The results show that methane fraction increase from almost zero percent to 14% at 25 bar. Since methane is not a favorable outcome of this system, elevated pressure has adverse effect on the total system performance and consequently system efficiency drops by about 20% points by increasing the electrolyser operating pressure from atmospheric to 25 bar. This effect also results in higher levelized cost of syngas at elevated pressures. Effects of other operating parameters like temperature and utilization factor on the syngas production rate and system performance are also explored. In addition, relative irreversibility of each component is estimated. It is concluded that the solid oxide electrolyser has the highest relative irreversibility amongst other system components which can be minimized by changing operating temperature. At last but not least, levelized cost of produced syngas is estimated. [ABSTRACT FROM AUTHOR]

In this work, perovskite Sr 1−x Pr x FeO 3-δ (SPF) (x = 0.02, 0.04, 0.06, 0.08 and 0.10) are investigated and employed as solid oxide steam electrolyser cathode at 800 °C. X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM) analysis together indicate that the Sr 1−x Pr x FeO 3-δ is redox reversible with a phase transition from cubic to orthorhombic structure in redox cycles. The doping of Pr in A site has remarkably enhanced the electronic conduction to 1.0–1.2 S cm −1 at intermediate temperatures in reducing atmosphere. Electrochemical measurements demonstrate that the polarization resistance with Sr 0.96 Pr 0.04 FeO 3-δ electrode shows the lowest values of 0.25 Ω cm 2 in symmetric cells in reducing atmosphere at 800 °C. Direct steam electrolysis with Sr 0.96 Pr 0.04 FeO 3-δ cathode shows a current density of 1.64 A cm −2 at 2.0 V when fed with 5%H 2 O/Ar. The hydrogen production rate reaches 4.73, 6.68, 8.35 and 10.23 mL min −1 cm −2 at 1.4, 1.6, 1.8, 2.0 V, respectively, while the highest Faraday efficiency is as high as 97.16% at 1.8 V. [ABSTRACT FROM AUTHOR]

Production of synthetic hydrocarbon fuels as a means for renewable energy storage has gained attention recently. Integration of solid oxide co-electrolysis of steam and carbon dioxide with the Fischer-Tropsch process to transform renewable electricity into Fischer-Tropsch diesel is one of the promising suggested pathways. However, considering the intermittency of produced renewable electricity such integration will have a low capacity factor. Besides, locating a reliable source of carbon dioxide near the installed integrated system may prove to be difficult. A novel integration for production of Fischer-Tropsch diesel from various renewable sources is suggested in this study. The proposed integrated system includes solid oxide electrolysis, entrained gasification, Fischer-Tropsch process and an upgrading system. Gasification is assumed to have a continuous operation which increases capacity factor of the integrated system. Carbon dioxide supplied via gasification of biomass provides a reliable source for on-site co-electrolysis. Technical capabilities of the proposed integrated system examined by investigating performance in relation with electricity, and diesel demand of four different European cities. Results show that the proposed system is capable of supplying Fischer-Tropsch diesel of between 0.9–32% of the annual diesel demand for road transportation respective to the location of installation, with a high emission savings (around 100%). Cost of produced diesel is not competitive with conventional diesel for all cases, even when all the other by-products were assumed to be sold to the market.

CO 2 and/or H 2 O were reduced to CO/H 2 in micro-tubular solid oxide electrolysers with yttria-stabilized zirconia (YSZ) electrolyte, Ni-YSZ cermet cathode and strontium(II)-doped lanthanum manganite (LSM) oxygen-evolving anode. At 822 °C, the kinetics of CO 2 reduction were slower (ca. −0.49 A cm −2 at 1.8 V) than H 2 O reduction or co-reduction of CO 2 and H 2 O, which were comparable (ca. −0.83 to −0.77 A cm −2 at 1.8 V). Performances were improved (−0.85 and −1.1 A cm −2 for CO 2 and H 2 O electrolysis, respectively) by substituting the silver current collector with nickel and avoiding blockage of entrances to pores on the inner lumen of micro-tubes induced by silver paste applied previously to decrease contact losses. The change in current collector materials increased ohmic potential losses due to substituting the lower resistance Ag with Ni wire, but decreased electrode polarization losses by 80–93%. For co-electrolysis of CO 2 and H 2 O, isotopically-labelled C 18 O 2 was used to try to distinguish between direct cathodic reduction of CO 2 and its Ni-catalysed chemical reaction with hydrogen from reduction of steam. Unfortunately, oxygen was exchanged between C 18 O 2 and H 2 16 O, enriching oxygen-18 in the steam and substituting oxygen-16 in the carbon dioxide, so the anode off-gas isotopic fractions were meaningless. This occurred even in alumina and YSZ tubes without the micro-tubular reactor, i.e. in the absence of Ni catalyst, though not in quartz tubes. Unfortunately, larger differences between the thermal expansion coefficients of quartz and YSZ precluded using a quartz tube to house the micro-tubular reactor. However, the kinetic results, CO/H 2 yields from off-gas analysis, diffusional considerations and model predictions of reactant and product gas adsorption on Ni suggested that syngas should be produced by electrochemical reduction of steam to H 2 , followed by its Ni-catalysed chemical reaction with CO 2 . [ABSTRACT FROM AUTHOR]

A solid oxide electrolysis cell concept for reducing CO 2 to CO was studied using a proton conducting mixed oxide — BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.06 Zn 0.04 O 3 − δ (BCZYYZ) as an electrolyte. The oxide composite mixture: Ce 0.6 Mn 0.3 Fe 0.1 O 2 –La 0.6 Sr 0.4 Fe 0.9 Mn 0.1 O 3 (12.5–87.5 wt.%) was examined as enhancing catalyst electrode for CO 2 reduction and proton oxidation reaction on the cathode side for avoiding coke formation. Here we demonstrate the successful electrochemical reduction of CO 2 in proton conducting SOECs. During electrochemical reduction of CO 2 at 700 °C, current densities as high as 0.5 A/cm 2 and 1 A/cm 2 at 1.3 V and 2.2 V respectively, were withdrawn even though the cell employed a 400 μm thick BCZYYZ electrolyte support. [ABSTRACT FROM AUTHOR]

Hydrogen, combined with fuel cell technology, is an option for reducing our reliance on hydrocarbon-based fuels. Solid oxide electrolyser cells (SOECs) have been studied as a possible technology to produce hydrogen from steam. As the current global energy mix is heavily reliant on hydrocarbon-based fuels, utilising existing technologies such as coal fired power plants, combined with SOECs in an integrated system, may enable a path towards reducing carbon dioxide emissions as well as creating a way of introducing 'cleaner' fuel, In this work, a steady state model of a SOEC was developed and used to assess the feasibility of using hot steam from a power plant as feed to a SOEC. The main objective was to study the ways of improving the SOEC efficiency. The most favourable feed for the SOEC was to extract steam prior to the intermediate pressure turbine, which showed SOEC efficiency improvement of 25% compared with conventional SOEC operation of heating water at 25 °C. The thermoneutral point of 4644 A m-2 was shown to be a guide for assessing design and operation options with heat integration possibilities after this point. For scenarios of 7% steam extraction and a purely H2 production plant, 250 MW (7500 kgh-1) and 290 MW (8700 kgh-1) H2 can be produced with SOECs sized at 43,300 and 50,100 m², respectively. [ABSTRACT FROM AUTHOR]

The use of composite electrodes based on La0.7Sr0.3VO3 (LSV) for steam electrolysis has uncovered the tremendous potential and capacity inherent in this material. Unfortunately, this material has a major setback of inefficient electrolysis triggered by limited electrocatalytic activity. In this work, an infiltration method is employed to load catalytic-active metal nanoparticles onto the composite electrodes in order to achieve an activity-enhanced electrode performance. The electrical properties of LSV are methodically explored and correlated to electrode performance. At 800 °C in either pure H2 or low hydrogen partial pressure (pH2) of 5%H2/N2, the polarization resistance of symmetrical cells with Ni-loaded LSV (LSV-Ni) cathode is largely enhanced, in contrast to bare LSV cathode. Similar improvement is also achieved for the Fe-loaded LSV (LSV-Fe) cathode in a wide range of hydrogen partial pressures of 5%–100%. The Faraday efficiencies of LSV-Ni and LSV-Fe composite cathodes were remarkably improved for electrolysis in either 3%H2O/4.7H2/Ar or 3%H2O/Ar at 800 °C. [ABSTRACT FROM AUTHOR]

• Inkjet printing technique enables fabrication of three-dimensional electrode layer. • Circular pillar structure Ni(O)-YSZ electrode layer was printed using the technique. • The structure effectively enhanced interfacial area in the cell and performance. • The 3D structured cell showed ca. 50% improved peak power density in fuel cell mode. • In steam electrolysis mode, current density improved by a factor of 3. Increasing densities of (electrode–electrolyte-pore) triple phase boundaries (TPBs) / reaction sites enhance performances of solid oxide electrochemical reactors (SOERs) in both fuel cell (SOFC) and electrolyser (SOE) modes. Inkjet 3D printing is capable of construction of ceramic microstructures on support layers, enabling fabrication of SOERs with enhanced active area to geometric area ratios, thereby up-scaling effective areas / TBP lengths per unit volume. A Ni(O)-YSZ functional layer was designed and 3D inkjet printed with a surface of circular pillars, a facile geometry for printing that increased the interfacial to geometric area ratio. Deposition of further functional layers and sintering resulted in fully fabricated reactors with structures: H 2 O-H 2 | Ni(O)-YSZ support | Ni(O)-YSZ pillars | YSZ | YSZ-LSM | O 2 , Air. The corresponding planar structured cell also was fabricated with the same components, for comparison of its electrochemical performance with that of the pillar-structured cell. The latter exhibited performance enhancement over its planar counterpart by factors of ca. 1.5 in fuel cell mode, ca. 3 in steam electrolysis mode, and ca. 4–5 in CO 2 electrolysis mode, thereby demonstrating the potential of geometric structuring of electrode | electrolyte interfaces by 3D printing for developing higher performance SOERs. [ABSTRACT FROM AUTHOR]

The feasibility was investigated of using a Cu/CGO cathode for CO reduction to CO in a high temperature solid oxide electrolyser (CO-CO, Cu/CGO|YSZ|YSZ/LSM|LSM, ambient air). An adherent layer of porous Cu/CGO electrode on YSZ electrolyte was achieved by sintering Cu/CGO paste at 1,000 °C for 5 h. Comparable performance was obtained with Ni/YSZ and Cu/CGO cathodes for CO reduction at 750 °C and a 50:50 CO-CO feed; CO oxidation rates were faster than CO reduction rates. Ohmic and polarisation resistances of the Cu/CGO electrode all decreased with decreasing CO:CO feed ratio. In the electrolytic mode, 100 % current efficiency for CO reduction to CO was achieved on the Cu/CGO cathode at potential differences up to 1.5 V, above which the electronic conductivity of the YSZ electrolyte increased, causing a loss in effective current efficiency. Further increase in potential difference to ca. >2.3 V caused irreversible damage to the YSZ electrolyte due to its partial decomposition. No significant performance degradation, Cu sintering/migration, carbon deposition or electrode delamination was evident during 2 h of operating the electrolyser at 1.85 V and 750 °C for CO reduction with a Cu/CGO cathode. [ABSTRACT FROM AUTHOR]

Abstract: Composite cathodes based on La0.75Sr0.25Cr0.5Mn0.5O3−δ (LSCM) can perform direct steam electrolysis; however, the insufficient electro-catalytic activity still limits the electrode performances and Faradic efficiency. In this work, Fe catalyst is loaded onto an LSCM-based composite fuel electrode and studied for direct steam electrolysis. The dependence of the conductivity of LSCM on temperature and on oxygen partial pressure is investigated and correlated to the cathode performance. The loading of Fe catalysts significantly improved the electrode performance and the Faradic efficiency without the flow of reducing gas over the cathode. The current efficiency is enhanced by 30% and 40% compared to the values with the bare LSCM-based cathode at 800 °C in 3%H2O/5%H2/Ar and 3%H2O/Ar, respectively. The synergetic effect of catalytic-active Fe and redox-stable LSCM leads to excellent stability and better cathode performance for direct steam electrolysis. [Copyright &y& Elsevier]

Abstract: In this paper, we demonstrate the direct conversion of CO2/H2O into fuel in a proton-conducting solid oxide electrolyser with the configuration (La0.75Sr0.25)0.95Mn0.5Cr0.5O3−δ (LSCM, oxygen electrode)/BaCe0.5Zr0.3Y0.16Zn0.04O3−δ (BCZYZ, proton-conducting electrolyte)/Ni (fuel electrode) at 600 °C, where 5% H2O/Ar and 100% CO2 are fed into the oxygen electrode and fuel electrode, respectively. AC impedance spectroscopy and I–V testing demonstrate two main processes in the electrochemical process from 0 to 2 V: (1) the reoxidation of the LSCM electrode (Mn3± → Mn4±) below 1.2 V (iR-corrected voltage) and (2) the oxidation of H2O (H2O − 2e → H± ± 1/2O2) above 1.2 V (iR-corrected voltage). The current density reaches ∼0.1 Acm−2 at 2 V versus open circuit voltage (OCV) with a total polarisation resistance of 7.5 Ωcm2. Steam is steadily electrolysed under a 2 V load at 600 °C, and the generated protons in the fuel electrode are simultaneously and completely utilised to electrochemically reduce CO2 with 100% selectivity and ∼90% current efficiency to CO fuel. However, the carbon deposition, poisoning and oxidation of Ni metal in the fuel electrode degrade the cell performance. [Copyright &y& Elsevier]

• A hybrid method is developed to predict the performance of SOEC. • The hybrid model shows high accuracy at a wide range of operating conditions. • The computational cost is significantly reduced with AI assistance. • Optimised working parameters is quickly predicted at the thermal-neutral condition. High-temperature co-electrolysis of CO 2 /H 2 O through the solid oxide electrolysis cells (SOECs) is a promising method to generate renewable fuels and chemical feedstocks. Applying this technology in flexible scenario, especially when combined with variable renewable powers, requires an efficient optimisation strategy to ensure its safety and cost-effective in the long-term operation. To this purpose, we present a hybrid simulation method for the accurate and fast optimisation of the co-electrolysis process in the SOECs. This method builds multi-physics models based on experimental data and extends the database to develop the deep neural network and genetic algorithm. In the case study, thermal-neutral condition (TNC) is set as the optimisation target in various operating conditions, where the SOEC generates no waste heat and needs no auxiliary heating equipment. Small peak-temperature-gradient (PTG) inside the SOEC is found at the TNC, which is vital to prevent thermal failure in the operation. For the cell operating with 1023 K and 1123 K of inlet gas temperatures, the smallest PTGs reach 0.09 and 0.31 K mm−1 at 1.13 and 1.19 V, respectively. Finally, a 4-D map is presented to show the interactions among the applied voltage, required power density, inlet gas composition, and temperature under the TNC. The proposed method can be flexibly modified based on different optimisation targets for various applications in the energy sector. [ABSTRACT FROM AUTHOR]

Production of synthetic hydrocarbon fuels as a means for renewable energy storage has gained attention recently. Integration of solid oxide co-electrolysis of steam and carbon dioxide with the Fischer-Tropsch process to transform renewable electricity into Fischer-Tropsch diesel is one of the promising suggested pathways. However, considering the intermittency of produced renewable electricity such integration will have a low capacity factor. Besides, locating a reliable source of carbon dioxide near the installed integrated system may prove to be difficult. A novel integration for production of Fischer-Tropsch diesel from various renewable sources is suggested in this study. The proposed integrated system includes solid oxide electrolysis, entrained gasification, Fischer-Tropsch process and an upgrading system. Gasification is assumed to have a continuous operation which increases capacity factor of the integrated system. Carbon dioxide supplied via gasification of biomass provides a reliable source for on-site co-electrolysis. Technical capabilities of the proposed integrated system examined by investigating performance in relation with electricity, and diesel demand of four different European cities. Results show that the proposed system is capable of supplying Fischer-Tropsch diesel of between 0.9–32% of the annual diesel demand for road transportation respective to the location of installation, with a high emission savings (around 100%). Cost of produced diesel is not competitive with conventional diesel for all cases, even when all the other by-products were assumed to be sold to the market. [ABSTRACT FROM AUTHOR]