Project description:Tremendous efforts to develop high-efficiency reduced-temperature (≤ 600°C) solid oxide fuel cells are motivated by their potentials for reduced materials cost, less engineering challenge, and better performance durability. A key obstacle to such fuel cells arises from sluggish oxygen reduction reaction kinetics on the cathodes. Here we reported that an oxide hybrid, featuring a nanoporous Sm(0.5)Sr(0.5)CoO(3-δ) (SSC) catalyst coating bonded onto the internal surface of a high-porosity La(0.9)Sr(0.1)Ga(0.8)Mg(0.2)O(3-δ) (LSGM) backbone, exhibited superior catalytic activity for oxygen reduction reactions and thereby yielded low interfacial resistances in air, e.g., 0.021 Ω cm(2) at 650°C and 0.043 Ω cm(2) at 600°C. We further demonstrated that such a micro-nano porous hybrid, adopted as the cathode in a thin LSGM electrolyte fuel cell, produced impressive power densities of 2.02 W cm(-2) at 650°C and 1.46 W cm(-2) at 600°C when operated on humidified hydrogen fuel and air oxidant.
Project description:Reversible solid oxide fuel cell (RSOFC) is an energy device that flexibly interchanges between electrical and chemical energy according to people's life and production needs. The development of cell materials affects the stability and cost of the cell, but also restricts its market-oriented development. After decades of research by scientists, a lot of achievements and progress have been made on RSOFC materials. According to the composition and requirements of each component of RSOFC, this article summarizes the research progress based on materials and discusses the merits and demerits of current cell materials in electrochemical performance. According to the efficiency of different materials in solid oxide fuel cell (SOFC mode) and solid oxide electrolyzer (SOEC mode), the challenges encountered by RSOFC in the operation are evaluated, and the future development of RSOFC materials is boldly prospected.
Project description:Heterostructured composite ceria electrolytes have been shown to accelerate the oxygen reduction activity and provide a new approach to improve solid oxide fuel cell (SOFC) performance. In this study, barium carbonate was added to gadolinium-doped ceria, Gd0.2Ce0.8O2-δ (GDC) electrolyte to improve the electrochemical performance of intermediate-temperature SOFCs. The heterostructured electrolyte was formed by the addition of 5 wt % BaCO3 to a GDC electrolyte, resulting in a reaction during sintering that formed well-dispersed BaCe0.8Gd0.2O3-δ (BCG) throughout the electrolyte. The resulting material was tested as an electrolyte using La0.6Sr0.4Co0.2Fe0.8O3-δ as a cathode, resulting in a dramatic reduction to the polarization resistance of more than half the value (600 and 700 °C, the resistance was reduced from 2.49 and 0.23 Ω cm2 to 1.21 and 0.12 Ω cm2) obtained by using pure GDC as an electrolyte. Furthermore, full cell SOFC tests employing the heterostructured electrolyte conducted during overextended durations indicated that the BCG phase in the 5BCG-GDC electrolyte was stable in an air atmosphere with no observed reactions with residual CO2. This approach of tailoring surface reactivity by tailoring the composition and structure of the electrolyte as opposed to electrode materials provides an alternative method to improve fuel cell performance.
Project description:Thermal management of SOFCs (solid oxide fuel cell) is important for helping to minimise high temperature-related performance losses and maximising cell/stack lifetime. Thin film sensor technology is proposed as an excellent candidate to measure the cell temperature during operation due to its negligible mass, minimal disturbance to normal operation and higher temporal and spatial resolutions. However, the effective application of such sensors in SOFC systems is a challenging endeavour and predicated on incorporating the external wire attachments to complete the electrical circuit. This is because of the high sensitivity of SOFC materials to any interference to operation, limited available space and harsh operating conditions. In this paper, a new concept of packaging external wire attachments to the thin film sensor is described to enable the integration of the sensor in the SOFC system. Temperature measurements have been monitored under OCV and operating condition with the thin film sensor directly from SOFC cathode surface via proposed spring-based wire connection, from room temperature to SOFC operating temperature. The impact of the parameters including contact resistance (Rc) between sensor pads and attached wire on monitored temperature has also been analysed with the contribution of conductive paste. High temporal and spatial resolutions have been obtained with the implemented sensor.
Project description:This study aims to investigate the implications of transition-metal Zn doping at the B-site on the crystal structure, average thermal expansion coefficient (TEC), electrocatalytic activity, and electrochemical performance of LaBaFe2O5+δ by preparing LaBaFe2-xZnxO5+δ (x = 0, 0.05, 0.1, 0.15, 0.2, LBFZx). The X-ray diffraction (XRD) results show that Zn2+ doping does not change the crystal structure, the unit cell volume increases, and the lattice expands. The X-ray photoelectron spectroscopy (XPS) and mineral titration results show that the oxygen vacancy concentration and Fe4+ content gradually increase with the increase in doping amount. TEC decreases with the increase in Zn2+ doping amount, and the TEC of LBFZ0.2 is 11.4 × 10-6 K-1 at 30-750 °C. The conductivity has the best value of 103 S cm-1 at the doping amount of x = 0.1. The scanning electron microscopy (SEM) images demonstrate that the electrolyte CGO(Gd0.1Ce0.9O1.95) becomes denser after high-temperature calcination, and the cathode material is well attached to the electrolyte. The electrochemical impedance analysis shows that Zn2+ doping at the B-site can reduce the (Rp) polarization resistance, and the Rp value of the symmetric cell with LaBaFe1.8Zn0.2O5+δ as cathode at 800 °C is 0.014 Ω cm2. The peak power density (PPD) value of the anode-supported single cell is 453 mW cm-2, which shows excellent electrochemical performance.
Project description:A cobalt-based thermoelectric compound Ca(3)Co(2)O(6) (CCO) has been developed as new cathode material with superior performance for intermediate-temperature (IT) solid-oxide fuel cell (SOFC). Systematic evaluation has been carried out. Measurement of thermal expansion coefficient (TEC), thermal-stress (?) and interfacial shearing stress (?) with the electrolyte show that CCO matches well with several commonly-used IT electrolytes. Maximum power density as high as 1.47 W cm(-2) is attained at 800°C, and an additional thermoelectric voltage of 11.7 mV is detected. The superior electrochemical performance, thermoelectric effect, and comparable thermal and mechanical behaviors with the electrolytes make CCO to be a promising cathode material for SOFC.
Project description:Correlating the microstructure of an energy conversion device to its performance is often a complex exercise, notably in solid oxide fuel cell research. Solid oxide fuel cells combine multiple materials and interfaces that evolve in time due to high operating temperatures and reactive atmospheres. We demonstrate here that operando environmental transmission electron microscopy can identify structure-property links in such devices. By contacting a cathode-electrolyte-anode cell to a heating and biasing microelectromechanical system in a single-chamber configuration, a direct correlation is found between the environmental conditions (oxygen and hydrogen partial pressures, temperature), the cell open circuit voltage, and the microstructural evolution of the fuel cell, down to the atomic scale. The results shed important insights into the impact of the anode oxidation state and its morphology on the cell electrical properties.
Project description:Yb3+ and Y3+ double doped ZrO? (8YSZ+4Yb?O?) samples were synthesized by a solid state reaction method. Moreover, 8YSZ+4Yb?O?-NaCl/KCl composites were also successfully produced at different temperatures. The 8YSZ+4Yb?O?, 8YSZ+4Yb?O?-NaCl/KCl (800 °C), and 8YSZ+4Yb?O?-NaCl/KCl (1000 °C) samples were characterized by x?ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that a dense composite electrolyte was formed at a low temperature of 800 °C. The maximum conductivities of 4.7 × 10-2 S·cm-1, 6.1 × 10-1 S·cm-1, and 3.8 × 10-1 S·cm-1 were achieved for the 8YSZ+4Yb?O?, 8YSZ+4Yb?O?-NaCl/KCl (800 °C), and 8YSZ+4Yb?O?-NaCl/KCl (1000 °C) samples at 700 °C, respectively. The log?~log (pO?) plot result showed that the 8YSZ+4Yb?O?-NaCl/KCl (800 °C) composite electrolyte is a virtually pure ionic conductor. An excellent performance of the 8YSZ+4Yb?O?-NaCl/KCl (800 °C) composite was obtained with a maximum power density of 364 mW·cm-2 at 700 °C.
Project description:Low-temperature solid oxide fuel cells (LT-SOFCs) are a promising next-generation fuel cell due to their low cost and rapid start-up, posing a significant challenge to electrode materials with high electrocatalytic activity. Herein, we reported the bimetallic nanoparticles encapsulated in carbon nanotubes (NiFe@CNTs) prepared by carefully controlling catalytic pyrolysis of waste plastics. Results showed that plenty of multi-walled CNTs with outer diameters (14.38 ± 3.84 nm) were observed due to the smallest crystalline size of Ni-Fe alloy nanoparticles. SOFCs with such NiFe@CNTs blended in anode exhibited remarkable performances, reaching a maximum power density of 885 mW cm-2 at 500°C. This could be attributed to the well-dispersed alloy nanoparticles and high graphitization degree of NiFe@CNTs to improve HOR activity. Our strategy could upcycle waste plastics to produce nanocomposites and demonstrate a high-performance LT-SOFCs system, addressing the challenges of sustainable waste management and guaranteeing global energy safety simultaneously.
Project description:The chemical instability of perovskite oxides containing Sr is a critical issue for the long-term operation of solid oxide fuel cells. In this study, we demonstrate a remarkable improvement in the chemical and electrochemical stability of a heterostructured La0.6Sr0.4CoO3-δ (LSC)-Ce0.9Gd0.1O1.95 (GDC) electrode. Electrostatic spray deposition was employed to fabricate heterostructured nanoparticles in a single step with a coaxial nozzle supplying the LSC powders in the core nozzle and the GDC precursors in the shell nozzle. Moreover, the reducing fuel added to the GDC precursor solution induced the sol-gel combustion reaction in the droplet to form a uniform nanocrystalline GDC coating with high surface coverage. The high surface coverage of GDC on the LSC more significantly improved long-term stability compared with than of the bare LSC cathode at a constant current density of 1 A/cm2 at 600°C for 100 h.