Minfang Han

Sulfur‐Tolerant Redox‐Reversible Anode Material for Direct Hydrocarbon Solid Oxide Fuel Cells

A novel composite anode material consisting of K(2) NiF(4) -type structured Pr(0.8) Sr(1.2) (Co,Fe)(0.8) Nb(0.2) O(4+δ) (K-PSCFN) matrix with homogenously dispersed nano-sized Co-Fe alloy (CFA) has been obtained by annealing perovskite Pr(0.4) Sr(0.6) Co(0.2) Fe(0.7) Nb(0.1) O(3-δ) (P-PSCFN) in H(2) at 900 °C. The K-PSCFN-CFA composite anode is redox-reversible and has demonstrated similar catalytic activity to Ni-based cermet anode, excellent sulfur tolerance, remarkable coking resistance and robust redox cyclability.

Hierarchically Oriented Macroporous Anode-Supported Solid Oxide Fuel Cell with Thin Ceria Electrolyte Film

Application of anode-supported solid oxide fuel cell (SOFC) with ceria based electrolyte has often been limited by high cost of electrolyte film fabrication and high electrode polarization. In this study, dense Gd0.1Ce0.9O2 (GDC) thin film electrolytes have been fabricated on hierarchically oriented macroporous NiO-GDC anodes by a combination of freeze-drying tape-casting of the NiO-GDC anode, drop-coating GDC slurry on NiO-GDC anode, and co-firing the electrolyte/anode bilayers. Using 3D X-ray microscopy and subsequent analysis, it has been determined that the NiO-GDC anode substrates have a porosity of around 42% and channel size from around 10 μm at the electrolyte side to around 20 μm at the other side of the NiO-GDC (away from the electrolyte), indicating a hierarchically oriented macroporous NiO-GDC microstructure. Such NiO-GDC microstructure shows a tortuosity factor of ∼1.3 along the thickness direction, expecting to facilitate gas diffusion in the anode during fuel cell operation. SOFCs with such Ni-GDC anode, GDC film (30 μm) electrolyte, and La0.6Sr0.4Co0.2Fe0.8O3-GDC (LSCF-GDC) cathode show significantly enhanced cell power output of 1.021 W cm(-2) at 600 °C using H2 as fuel and ambient air as oxidant. Electrochemical Impedance Spectroscopy (EIS) analysis indicates a decrease in both activation and concentration polarizations. This study has demonstrated that freeze-drying tape-casting is a very promising approach to fabricate hierarchically oriented porous substrate for SOFC and other applications.

The influence of α-Al2O3 addition on microstructure, mechanical and formaldehyde adsorption properties of fly ash-based geopolymer products.

Fly ash-based geopolymer with α-Al(2)O(3) addition were synthesized and used to remove formaldehyde from indoor air. The microstructure, mechanical and formaldehyde adsorption properties of the geopolymer products obtained were investigated. The results showed that α-Al(2)O(3) addition with appropriate amount (such as 5 wt%) increased the geopolymerization extent, resulting in the increase of surface area and compressive strength. In addition, the improvement of structural ordering level for geopolymer sample with 5 wt% α-Al(2)O(3) addition was found through FTIR analysis. By contrast, excessive addition (such as 10 wt%) had the opposite effect. The test of formaldehyde adsorption capacity confirmed that fly ash-based geopolymer product exhibited much better property of adsorbing indoor formaldehyde physically and chemically than fly ash itself. The surface area was an important but not unique factor influencing the adsorption capacity of geopolymers.

HIGH PERFORMANCE LOW TEMPERATURE SOLID OXIDE FUEL CELLS WITH NOVEL ELECTRODE ARCHITECTURE

In this study, we have fabricated high performance low temperature solid oxide fuel cells (LT-SOFCs) with both acicular anodes and cathodes with thin Gd-doped ceria (GDC) electrolyte film. The acicular Ni-Gd0.1Ce0.9O2−δ (Ni-GDC) anode was prepared using freeze drying tape casting, while the hierarchically porous cathode with nano-size Sm0.5Sr0.5CoO3 (SSC) particles covering an acicular GDC skeleton was prepared by a combination of freeze drying tape casting and self-rising approaches. The acicular electrodes with 5–200 μm pores/channels enhance mass transport, while SSC particles of about 50 nm in the cathode promote electrochemical reactions. Cells which have this novel electrode architecture show a significantly high power output of 1.44 W cm−2 and an extremely low cell polarization resistance of 0.0379 Ω cm2 at 600 °C.

Influence of Lithium Oxide Addition on the Sintering Behavior and Electrical Conductivity of Gadolinia Doped Ceria

Ceria-based electrolytes have been widely researched in intermediate-temperature solid oxide fuel cell (SOFC), which might be operated at 500–600°C. Sintering behavior with lithium oxide as sintering additive and electrical conductivity of gadolinia doped ceria (Gd 0.1 Ce 0.9 O 2-δ , GDC10) electrolyte was studied in this paper by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). As the results, the fully dense GDC10 electrolytes are obtained at a low temperature of 800°C with 2.5 mol% Li 2 O as sintering additive (called 5UGDC800). During sintering process, lithium oxides adsorbed by around GDC10 surface help to sinter at 800°C and are kept at the grain boundary of GDC10 in the end. The fine grains of 100–400 nm and high electrical conductivity of 0.014 S/cm at 600°C in 5LiGDC800 were achieved, which contributed to the lower sintering temperature and enhanced grain boundary conductivity, respectively. Lithium, staying at grain boundary, reduces the depletion of oxygen vacancies in the space charge layers and increases the oxygen vacancy concentration in the grain boundary, which leads to improve the total electrical conductivity of 5LiGDC800.

La0.7Sr0.3Fe0.7Ga0.3O3−δ as electrode material for a symmetrical solid oxide fuel cell

In this research, La0.7Sr0.3Fe0.7Ga0.3O3−δ (LSFG) perovskite oxide was successfully prepared using a microwave-assisted combustion method, and employed as both anode and cathode in symmetrical solid oxide fuel cells. A maximum power density of 489 mW cm−2 was achieved at 800 °C with wet H2 as the fuel and ambient air as the oxidant in a single cell with the configuration LSFG|La0.8Sr0.2Ga0.83Mg0.17O3−δ|LSFG. Furthermore, the cells demonstrated good stability in H2 and acceptable sulfur tolerance.

Facile and sustainable synthesis of sodium lignosulfonate derived hierarchical porous carbons for supercapacitors with high volumetric energy densities

Interconnected hierarchical porous carbon was successfully prepared by direct carbonization of industrial waste sodium lignosulfonate without additional templating and activation agents. The as-prepared carbon sample shows a moderate specific surface area of 903 m2 g−1 and high contents of 8.11 at% oxygen and 1.76 at% nitrogen, which could improve the electrolyte-affinitive surface area in an aqueous electrolyte. When used as electrode materials for symmetric supercapacitors in 7 M KOH electrolytes, the as-synthesized carbon sample exhibits a significantly high gravimetric capacitance of 247 F g−1, a volumetric capacitance of 240 F cm−3, and an areal capacitance of 27.4 μF cm−2 at a current density of 0.05 A g−1. Moreover, a superior energy density of 8.4 W h L−1 (at 13.9 W L−1) and a power density of 5573.1 W L−1 (at 3.5 W h L−1), as well as a remarkable cycling stability after 20 000 cycles at two different current densities were achieved for the assembled supercapacitors.

Remarkable O2 permeation through a mixed conducting carbon capture membrane functionalized by atomic layer deposition

The development of energy-efficient and cost-competitive carbon capture technology is of vital importance to effective reduction of carbon emissions and mitigation of global climate change. The present work reports that a highly energy-efficient electrochemical carbon capture membrane consisting of a carbonate and silver phase exhibits a remarkably high rate of O2 permeation after the silver phase is functionalized with a nanoscale layer of Al2O3 by atomic layer deposition. The resulting permeation flux ratio of O2 to CO2 was 1.5:1, a complete reversal from 1:2 of the conventional membrane. The mechanisms of this exceptionally high rate of O2 permeation were investigated by in situ Raman spectroscopy and theoretical DFT calculations. The results revealed that LiCO4− as the active surface species was responsible for the enhanced O2 permeation. A new CO2/O2 transport model based on a “cogwheel” migration mechanism of CO42− was presented to explain the experimental results with excellent agreement.

Research on sintering process of YSZ electrolyte

Abstract Yttria stabilized zirconia (YSZ) has widely been used as electrolyte in solid oxide fuel cell (SOFC). The microstructure of YSZ related to the fabrication process was discussed in the paper. With YSZ nano-powders about 40–100 nm as raw material, the YSZ adobe was manufactured by tape calendering process. The named three-step sintering process was performed at 1000 °C for 2 h, then raised the temperature with normal rate and as soon as up to 1400 °C, the furnace was controlled at 1250–1300 °C for 10–20 h. The high dense YSZs with the relative density of 96%-99% were obtained; the grain size of YSZ could be reduced to 0.5–3 μm. The above result is benefited to co-fired in the electrode-supported SOFCs.

Optimization of Sm0.5Sr0.5CoO3−δ-infiltrated YSZ electrodes for solid oxide fuel cell/electrolysis cell

The Sm0.5Sr0.5CoO3−δ (SSC) oxygen electrode has attracted much interest due to its high electrical conductivity and electrochemical activity. In this work, a SSC–YSZ (yttria stabilized zirconia) composite electrode was prepared by an infiltration process. First, cells with different SSC contents in the oxygen electrode and different sintering temperatures were prepared and tested in solid oxide fuel cell (SOFC) mode. An optimal cell with an SSC content of 45 wt% and sintering temperature of 850 °C shows favorable microstructure and relatively lower polarization resistance. The peak power densities of 0.96 W cm−2 and polarization resistances as low as 0.39 Ω cm−2 were obtained at 750 °C. Then, in solid oxide electrolysis cell (SOEC) mode, the effects of CO2/H2O ratio were investigated. Results indicated that the CO2/H2O ratio has little influence on the electrolysis performance in the range of 1 : 2–2 : 1. Finally, the electrochemical stability of the cell in both modes was tested at 750 °C for about 100 h. After a slight degradation in the initial 25 h, the cell showed good stability in SOFC mode, and no visible degradation was detected in SOEC mode in 100 h operation.