Zhongliang Zhan

A thermally self-sustained micro solid-oxide fuel-cell stack with high power density

High energy efficiency and energy density, together with rapid refuelling capability, render fuel cells highly attractive for portable power generation. Accordingly, polymer-electrolyte direct-methanol fuel cells are of increasing interest as possible alternatives to Li ion batteries. However, such fuel cells face several design challenges and cannot operate with hydrocarbon fuels of higher energy density. Solid-oxide fuel cells (SOFCs) enable direct use of higher hydrocarbons, but have not been seriously considered for portable applications because of thermal management difficulties at small scales, slow start-up and poor thermal cyclability. Here we demonstrate a thermally self-sustaining micro-SOFC stack with high power output and rapid start-up by using single chamber operation on propane fuel. The catalytic oxidation reactions supply sufficient thermal energy to maintain the fuel cells at 500–600 °C. A power output of ∼350 mW (at 1.0 V) was obtained from a device with a total cathode area of only 1.42 cm2.

A reduced temperature solid oxide fuel cell with nanostructured anodes

Reduced-temperature solid oxide fuel cells (SOFCs), featuring thin strontium- and magnesium-doped lanthanum gallate (LSGM) electrolytes and nano-scale Ni anodes, showed high power densities of 1.20 W cm−2 at 650 °C and 0.39 W cm−2 at 550 °C when operated on humidified hydrogen fuel and air oxidant.

A solid oxide cell yielding high power density below 600 °C

Here we report solid oxide cells with thin strontium- and magnesium-doped lanthanum gallate electrolytes that yield power densities of 1.06 W cm−2 at 550 °C and 0.81 W cm−2 at 500 °C when operated on humidified hydrogen and ambient air. Cost-effective ceramic processing and chemical solution impregnation methods were utilized, yielding a dual micron- and nano-scale architecture that is essential for achieving good low-temperature performance.

A micro-nano porous oxide hybrid for efficient oxygen reduction in reduced-temperature solid oxide fuel cells.

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 Sm0.5Sr0.5CoO3−δ (SSC) catalyst coating bonded onto the internal surface of a high-porosity La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) backbone, exhibited superior catalytic activity for oxygen reduction reactions and thereby yielded low interfacial resistances in air, e.g., 0.021 Ω cm2 at 650°C and 0.043 Ω cm2 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.

Shape‐Dependent Activity of Ceria for Hydrogen Electro‐Oxidation in Reduced‐Temperature Solid Oxide Fuel Cells

Single crystalline ceria nanooctahedra, nanocubes, and nanorods are hydrothermally synthesized, colloidally impregnated into the porous La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) scaffolds, and electrochemically evaluated as the anode catalysts for reduced temperature solid oxide fuel cells (SOFCs). Well-defined surface terminations are confirmed by the high-resolution transmission electron microscopy--(111) for nanooctahedra, (100) for nanocubes, and both (110) and (100) for nanorods. Temperature-programmed reduction in H2 shows the highest reducibility for nanorods, followed sequentially by nanocubes and nanooctahedra. Measurements of the anode polarization resistances and the fuel cell power densities reveal different orders of activity of ceria nanocrystals at high and low temperatures for hydrogen electro-oxidation, i.e., nanorods > nanocubes > nanooctahedra at T ≤ 450 °C and nanooctahedra > nanorods > nanocubes at T ≥ 500 °C. Such shape-dependent activities of these ceria nanocrystals have been correlated to their difference in the local structure distortions and thus in the reducibility. These findings will open up a new strategy for design of advanced catalysts for reduced-temperature SOFCs by elaborately engineering the shape of nanocrystals and thus selectively exposing the crystal facets.

Ni doped La 0.6 Sr 0.4 FeO 3- δ symmetrical electrode for solid oxide fuel cells

The conventional Ni cermet anode suffers from severe carbon deposition and sulfur poisoning when fossil fuels are used. Alternative anode materials are desired for high performance hydrocarbon fuel solid oxide fuel cells (SOFCs). We report the rational design of a very active Ni doped La 0.6 Sr 0.4 FeO 3- δ (LSFN) electrode for hydrocarbon fuel SOFCs. Homogeneously dispersed Ni-Fe alloy nanoparticles were in situ extruded onto the surface of the LSFN particles during the operation of the cell. Symmetric SOFC single cells were prepared by impregnating a LSFN precursor solution onto a YSZ (yttria stabilized zirconia) monolithic cell with a subsequent heat treatment. The open circuit voltage of the LSFN symmetric cell reached 1.18 and 1.0 V in humidified C 3 H 8 and CH 4 at 750 ℃, respectively. The peak power densities of the cells were 400 and 230 mW/cm 2 in humidified C 3 H 8 and CH 4 , respectively. The electrode showed good stability in long term testing, which revealed LSFN has good catalytic activity for hydrocarbon fuel oxidation.

Highly efficient electrolysis of pure CO2 with symmetrical nanostructured perovskite electrodes

A novel symmetrical cell was prepared by facile tape-casting and infiltration methods. The cell is ideal for CO2 electrolysis, achieving a current density of 1.24 A cm−2, which could be attributed to the significantly extended active sites resulting from novel architectures with infiltrated Sr2FeMoO6 (SFM) nano-networks. The combined strategy appears to be a promising approach to produce unique architectures for CO2 electrolysis with solid oxide electrolysis cells (SOECs).

La0·8Sr0·2Cr0·5Fe0·5O3-d as anode material on cathode-support SOFCs for direct hydrocarbon utilisation

Abstract Perovskite oxides have some advantages compared with metal oxides when used for hydrocarbon fuel. La0·8Sr0·2Cr0·5Fe0·5O3-d (LSCF) was prepared by the sol–gel method. X-ray diffraction shows that pure perovskite phases of LSCF were obtained at 1100°C. Catalytic properties and conductivity were investigated by temperature-programmed reduction and the four-probe method. Finally, utilising tape casting and lamination, we fabricated a cathode-support SOFC with a LSCF-Zr0·89Sc0·1Ce0·01O2-x(SSZ) anode by a one-time co-sintering process at 1250°C. The performance of the functioning fuel cell and a short-term stability test were investigated both in H2 and CH4 fuels. The result show that LSCF is a possible electrode material for future applications.

Metal supported solid oxide fuel cells with infiltrated nanoelectrodes

Abstract Novel metal supported solid oxide fuel cells (SOFCs) containing porous 430L support, yttria stabilised zirconia (YSZ) electrolyte and porous YSZ layer are fabricated by tape casting, tape lamination and subsequent cofiring in a reduced atmosphere. Nano Ni–Ce0·8Sm0·2O2−δ (SDC) and La0·8Sr0·2FeO3−δ (LSF) particles, which act as anode and cathode catalysts, individually, are infiltrated onto the internal surfaces of porous 430L and YSZ respectively. Maximum power density of the single cell is 850 mW cm−2 at 800°C. Encouraging performances of the infiltrated electrodes are also achieved, e.g. 0·06 Ω cm2 for the LSF infiltrated YSZ composite cathode and 0·075 Ω cm2 for the Ni-SDC infiltrated 430L composite anode at 800°C. Additionally, oxygen reduction kinetics over infiltrated LSF–YSZ composite cathodes is also studied.