17 Search Results

High‐temperature CO ₂ electrolysis via solid oxide electrolysis cells (CO ₂ –SOECs) has drawn special attention due to the high energy convention efficiency, fast electrode kinetics, and great potential in carbon cycling. However, the development of cathode materials with high catalytic activity and chemical stability for pure CO ₂ electrolysis is still a great challenge. In this work, A‐site cation deficient dual‐phase material, namely (Pr _0.4 Ca _0.6 ) _x Fe _0.8 Ni _0.2 O _3−δ (PCFN, x  = 1, 0.95, and 0.9), has been designed as the fuel electrode for a pure CO ₂ –SOEC, which presents superiormore » electrochemical performance. Among all these compositions, (Pr _0.4 Ca _0.6 ) _0.95 Fe _0.8 Ni _0.2 O _3−δ (PCFN95) exhibited the lowest polarization resistance of 0.458 Ω cm ² at open‐circuit voltage and 800 °C. The application of PCFN95 as the cathode in a single cell yields an impressive electrolysis current density of 1.76 A cm ⁻² at 1.5 V and 800 °C, which is 76% higher than that of single cells with stoichiometric Pr _0.4 Ca _0.6 Fe _0.8 Ni _0.2 O _3−δ (PCFN100) cathode. The effects of A‐site deficiency on materials' phase structure and physicochemical properties are also systematically investigated. Such an enhancement in electrochemical performance is attributed to the promotion of effective CO ₂ adsorption, as well as the improved electrode kinetics resulting from the A‐site deficiency.« less

Carbon dioxide (CO₂) is one of the principal greenhouse gases accountable for global warming and extreme climate changes. Electrochemically converting CO₂ into carbon monoxide (CO) is a promising approach for CO₂ utilization in achieving industrial decarbonization. High-temperature CO₂ electrolysis via solid oxide electrolysis cells (SOECs) has great potential, including high-energy efficiency, fast electrode kinetics, and competitive cost; however, this technology still has challenges associated with developing highly active, robust CO₂ electrodes for SOECs. We report novel Ruddlesden–Popper structured Pr_1.2Sr_0.8Mn_0.4Fe_0.6O_4–δ (RP-PSMF) with in situ exsolved Fe nanoparticles as the CO₂ electrode in SOECs for direct CO₂ conversion to CO. The mechanismmore » of CO₂ electrolysis is studied by using the distribution of relaxation times method from electrochemical impedance spectroscopy. La_0.8Sr_0.2Ga_0.8Mg_0.2O_3–δ (LSGM)-electrolyte supported SOECs with the RP-PSMF cathode have achieved exceptionally high current densities of 2.90, 1.61, 0.91, and 0.48 A·cm^–2 at an applied voltage of 1.5 V at 800, 750, 700, and 650 °C, respectively. Moreover, SOECs with the RP-PSMF cathode have exhibited a stable electrolysis performance for 100 h under a current cycling operation. Here, these results suggest that RP-PSMF with exsolved Fe nanoparticles is a highly promising cathode for high-temperature direct CO₂ electrolysis cells.« less

Massive carbon dioxide (CO₂) emission from recent human industrialization has affected the global ecosystem and raised great concern for environmental sustainability. The solid oxide electrolysis cell (SOEC) is a promising energy conversion device capable of efficiently converting CO₂ into valuable chemicals using renewable energy sources. However, Sr-containing cathode materials face the challenge of Sr carbonation during CO₂ electrolysis, which greatly affects the energy conversion efficiency and long-term stability. Thus, A-site Ca-doped La1–_xCaxCo_0.2Fe_0.8O_3-δ (0.2 ≤ x ≤ 0.6) oxides are developed for direct CO₂ conversion to carbon monoxide (CO) in an intermediate-temperature SOEC (IT-SOEC). With a polarization resistance as low asmore » 0.18 O cm² in pure CO₂ atmosphere, a remarkable current density of 2.24 A cm^–2 was achieved at 1.5 V with La_0.6Ca_0.4Co_0.2Fe_0.8O_3-δ (LCCF64) as the cathode in La_0.8Sr_0.2Ga_0.83Mg_0.17O_3-δ (LSGM) electrolyte (300 µm) supported electrolysis cells using La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) as the air electrode at 800 °C. Furthermore, symmetrical cells with LCCF64 as the electrodes also show promising electrolysis performance of 1.78 A cm^–2 at 1.5 V at 800 °C. In addition, stable cell performance has been achieved on direct CO₂ electrolysis at an applied constant current of 0.5 A cm^–2 at 800 °C. The easily removable carbonate intermediate produced during direct CO₂ electrolysis makes LCCF64 a promising regenerable cathode. The outstanding electrocatalytic performance of the LCCF64 cathode is ascribed to the highly active and stable metal/perovskite interfaces that resulted from the in situ exsolved Co/CoFe nanoparticles and the additional oxygen vacancies originated from the Ca₂Fe₂O₅ phase synergistically providing active sites for CO₂ adsorption and electrolysis. Here this study offers a novel approach to design catalysts with high performance for direct CO₂ electrolysis.« less

Abstract Solid-oxide fuel cells (SOFCs) offer great promise for producing electricity using a wide variety of fuels such as natural gas, coal gas and gasified carbonaceous solids; however, conventional nickel-based anodes face great challenges due to contaminants in readily available fuels, especially sulphur-containing compounds. Thus, the development of new anode materials that can suppress sulphur poisoning is crucial to the realization of fuel-flexible and cost-effective SOFCs. In this work, La0.1Sr1.9Fe1.4Ni0.1Mo0.5O6–δ (LSFNM) and Pr0.1Sr1.9Fe1.4Ni0.1Mo0.5O6–δ (PSFNM) materials have been synthesized using a sol-gel method in air and investigated as anode materials for SOFCs. Metallic nanoparticle-decorated ceramic anodes were obtained by the reductionmore » of LSFNM and PSFNM in H2 at 850°C, forming a Ruddlesden–Popper oxide with exsolved FeNi3 bimetallic nanoparticles. The electrochemical performance of the Sr2Fe1.4Ni0.1Mo0.5O6–δ ceramic anode was greatly enhanced by La doping of A-sites, resulting in a 44% decrease in the polarization resistance in reducing atmosphere. The maximum power densities of Sr- and Mg-doped LaGaO3 (LSGM) (300 μm) electrolyte-supported single cells with LSFNM as the anode reached 1.371 W cm −2 in H2 and 1.306 W cm–2 in 50 ppm H2S–H2 at 850°C. Meanwhile, PSFNM showed improved sulphur tolerance, which could be fully recovered after six cycles from H2 to 50 ppm H2S–H2 operation. This study indicates that LSFNM and PSFNM are promising high-performance anodes for SOFCs.« less

Direct CO₂ electrolysis using solid oxide electrolysis cells (CO₂-SOECs) holds promise to efficiently convert carbon dioxide to carbon monoxide and oxygen. Cathodes with desirable catalytic activity and chemical stability play a critical role in the development of direct CO₂-SOECs. Although Sr₂Fe_1.5Mo_0.5O_6–δ (SFM) has exhibited promise for direct CO₂-SOECs due to its redox stability, it suffers from insufficient activity for the CO₂ reduction reaction (CO₂RR). Here we report interface engineering of nanosized Pr₆O₁₁ on the SFM cathode obtained through infiltration to promote the CO₂RR performance for direct CO₂-SOECs. The effect of Pr₆O₁₁ loading on the performance of the CO₂RR is systematicallymore » investigated. At 800 °C, the current density of the Pr₆O₁₁ infiltrated SFM cathode with an optimum Pr₆O₁₁ loading of 14.8 wt% reaches 1.61 A cm^–2 at 1.5 V, more than double that of the SFM cathode (0.76 A cm^–2) under the same operating conditions. X-ray photoelectron spectroscopy (XPS) characterization and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis indicate that the adsorption ability of CO₂ on the SFM cathode has been significantly improved by the formation of Pr₆O₁₁. Temperature-programmed desorption (TPD) of CO₂ measurements further manifest that a 14.8 wt% Pr₆O₁₁-SFM cathode has better CO desorption capacity. In addition, polarization resistance of the SFM cathode has significantly decreased with the addition of Pr₆O₁₁. Three-electrode measurement was used to analyze the improved electrode kinetics. Finally, these results demonstrate that the formation of Pr₆O₁₁ in the SFM cathode through infiltration is a promising approach for increasing CO₂RR activity for CO₂-SOECs.« less

Abstract Metal‐supported solid oxide fuel cells (MS‐SOFCs) have been fabricated by applying phase‐inversion tape‐casting and atmospheric plasma spraying (APS). The effect of the binder amount of the phase‐inversion slurries on the microstructure development of the 430L stainless steel metal support was investigated. The pore structures, the viscosity of the slurry, porosity and permeability of the as‐prepared metal supports are significantly influenced by the amount of the binder. NiO–scandia‐stabilized zirconia (ScSZ) anode, ScSZ electrolyte and La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3−δ (LSCF) cathode layers were consecutively deposited on the metal support with an ideal microstructure by APSmore » process. The effect of plasma power of the APS on the microstructure of the electrolyte and cathode was investigated. A dense electrolyte layer and a porous cathode layer were successfully obtained at 40 and 6 kW of the APS plasma power, respectively. MS‐SOFCs, with a cell configuration of 430L/Ni‐ScSZ/ScSZ/LSCF, achieved a maximum cell power density of 1079 mW cm ⁻² at 700°C using humidified H ₂ as fuel and ambient air as oxidant. The corresponding ohmic resistance and total resistance of MS‐SOFCs was 0.14 and 0.32 Ω cm ² , respectively. This work demonstrates the feasibility of fabricating high‐performance MS‐SOFCs with economical and scalable techniques.« less

In symmetrical solid oxide fuel cells, comprehensively understanding the elementary reaction processes and the polarization behaviors of redox-stable electrode materials is critical for further optimization of the electrode performance. In this work, a systematical and practical approach, based on electrochemical impedance spectroscopy technology, is applied to identify the rate-limiting elementary reactions of the redox-stable electrodes. The feasibility of this proposed method is demonstrated in symmetrical solid oxide fuel cells with Sr₂Fe_1.5Mo_0.5O_6-σ-Ce_0.9Gd_0.1O_1.95 as electrodes. Based on the characteristic frequency ranges and the experimental results tested under various fuel gas components, operating temperatures, and discharge current densities, the rate-limiting steps of themore » cathode are associated with the formation of adsorbed oxygen ions and the combination of oxygen ions and oxygen vacancies, while the rate-limiting steps of the anode are ascribed to the hydrogen dissociated adsorption and the steam desorption processes. This experimental and analysis framework can be straightforwardly extended to other electrode materials to unravel their electrochemical performance in detail.« less

La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) is a common cathode material for intermediate temperature solid oxide fuel cells due to its excellent oxygen reduction reaction catalytic activity. However, the Cr-poisoning effect is a severe issue causing its electrochemical performance degrada-tion. To develop a LSCF-based cathode with excellent Cr-tolerance, LaCrO₃-coated LSCF core-shell structured (LCr@LSCF) cathode was prepared via solution infiltration method. After coated by LCr shell, the long-term stability and Cr-tolerance were obviously improved, at the price of sacrificing some electrochemical performance. As a result, the development of LCr@LSCF cathode with eye-catching Cr-tolerance is of great significance to the commercialization of LSCF.

The microstructure of the anode in anode-supported solid oxide fuel cells has significant influence on the cell performance. Here, microtubular Ni-yttria stabilized zircona (Zr_0.8Y_0.2O₂, YSZ) anode support has been prepared by the phase inversion method. Different compositions of non-solvent have been used for the fabrication of the Ni-YSZ anode support, and the correlation between non-solvent composition and characteristics of the microstructure of the anode support has been investigated. The presence of ethanol or isopropanol in the non-solvent can inhibit the growth of the finger-like pores in the anode support. With the increase of the concentration of ethanol or isopropanol inmore » the non-solvent, a thin dense layer can be observed on the top of the prepared tubular anode support. In addition, the mechanism of pore formation is explained based on the inter-diffusivity between the solvent and the non-solvent. Lastly, the prepared microtubular solid oxide fuel cells (MT-SOFCs) have been tested, and the influence of the anode microstructure on the cell electrochemical performance is analyzed based on a polarization model.« less

Sr₂Fe_1.5Mo_0.5O_6-δ (SFM) is a promising electrode material recently studied for intermediate temperature solid oxide fuel cells (IT-SOFCs). In this work, Cr-tolerance of SFM has been systematically assessed. Due to the presence of Sr at the A-site, SFM has been found to be vulnerable to Cr species resulted from the metallic interconnects. The main product of Cr-poisoning for SFM is SrCrO₄ deposited on the SFM surface. Furthermore, the Cr-poisoning mechanism of the SFM material has been evaluated both experimentally and thermodynamically. To enhance Cr-tolerance of SFM, LaCoO_3-δ-infiltrated SFM (LC@SFM) has been developed. LC hinders the direct contact of SFM with Crmore » species and LC@SFM has significantly enhanced Cr-tolerance than SFM. This study provides valuable guidance for the wide application of SFM cathode in IT-SOFCs.« less