Yttria-stabilized zirconia (YSZ) films were synthesized by atomic layer deposition (ALD). Tetrakis(dimethylamido)zirconium and tris(methylcyclopentadienyl)yttrium were used as ALD precursors with distilled water as oxidant. From X-ray photoelectron spectroscopy (XPS) compositional analysis, the yttria content was identified to increase proportionally to the pulse ratio of Y/Zr. Accordingly, the target stoichiometry ZrO2/Y2O3 = 0.92:0.08 was achieved. Crystal and grain structures of ALD YSZ films grown on amorphous Si3N4 were analyzed by X-ray diffraction (XRD) and atomic force microscopy (AFM). The microstructure of the polycrystalline films consisted of grains of tens of nanometers in diameter. To evaluate ALD YSZ films as oxide ion conductor, freestanding 60 nm films were prepared with porous platinum electrodes on both sides of the electrolyte. This structure served as a solid oxide fuel cell designed to operate at low temperatures. Maximum power densities of 28 mW/cm2, 66 mW/cm2, and 270 mW/cm2 were observed at 265 °C, 300 °C, and 350 °C, respectively. The high performance of thin film ALD electrolyte fuel cells is related to low electrolyte resistance and fast electrode kinetics. The exchange current density at the electrode−electrolyte interface was approximately 4 orders of magnitude higher compared to reference Pt-YSZ values.

Considerable attention has been focused on solid oxide fuel cells (SOFCs) due to their potential for providing clean and reliable electric power. However, the high operating temperatures of current SOFCs limit their adoption in mobile applications. To lower the SOFC operating temperature, we fabricated a corrugated thin-film electrolyte membrane by nanosphere lithography and atomic layer deposition to reduce the polarization and ohmic losses at low temperatures. The resulting micro-SOFC electrolyte membrane showed a hexagonal-pyramid array nanostructure and achieved a power density of 1.34 W/cm(2) at 500 °C. In the future, arrays of micro-SOFCs with high power density may enable a range of mobile and portable power applications.

Yttria-stabilized zirconia (YSZ) electrolyte membranes were surface modified by adding a 1 nm thin, high-yttria concentration YSZ film with the help of atomic layer deposition. The addition of the 1 nm film led to an increase of the maximum power density of a low-temperature solid oxide fuel cell (LT-SOFC) by a factor of 1.50 at 400 degrees C. The enhanced performance can be attributed to an increased oxide ion incorporation rate on the surface of the modified electrolyte.

No abstract

A critical bottleneck in reducing the operating temperature of solid-oxide fuel cells (SOFCs) is the sluggish reaction kinetics at the electrode/electrolyte interface. To improve SOFC performance at low temperatures, we combined atomic-layer deposition (ALD) and sputtering of platinum to create catalyst structures with high triple-phase-boundary (TPB) densities and low currentcollecting resistance. We studied the nucleation behavior of ALD platinum using plan-view transmission electron microscopy (TEM), and identifi ed deposition conditions that produced high TPB densities. A porous platinum layer was sputtered on top of the nanostructured ALD platinum layer, thereby reducing the resistance for current collection. A 90% increase in the fuel cell's peak power density was observed relative to catalyst structures that were deposited by sputtering only.SOFCs are known for their high energy-conversion effi ciency, as well as for the wide range of fuel usage in stationary applications. [1][2][3][4][5][6] However, the high operating temperatures of SOFCs have reduced their practicality for mobile applications. [ 7 , 8 ] Lowering the operating temperature adversely affects the rate of the oxygen-reduction reaction (ORR) and the hydrogen-oxidation reaction (HOR) at the electrode/electrolyte interfaces, thereby reducing the exchange current density and causing a drop in fuel-cell performance. To overcome this loss, we need, amongst other things, to search for catalyst structures that deliver fast reaction kinetics at comparatively low temperatures.One of the commonly used electrode-catalyst materials for low-temperature fuel cells is platinum. [ 9 , 10 ] Platinum can serve as an electrode for current collection and a catalyst for the ORR and the HOR. The superior catalytic capability of platinum provides high exchange-current densities in fuel cells operated at low temperatures. However, the exchange-current density is not only determined by the catalyst material, but also by the catalyst microstructure. [ 11 ] A key microstructural feature of the electrode catalyst is the TPB, where the electrode catalyst, gas, and electrolyte meet. Increasing the TPB density provides more reaction sites per unit area, resulting in a higher exchange-current density. Therefore, optimizing the platinum microstructure can signifi cantly improve the electrochemical performance of the platinum electrode catalyst.A common approach to fabricating high-TPB-density platinum catalysts is by DC magnetron sputtering at elevated pressures. [ 12 , 13 ] This approach provides for a simple way to obtain microporous electrode-catalyst structures. Alternative methods for fabricating platinum catalysts include lithography, such as e-beam lithography or nanosphere lithography. [14][15][16] The characteristic length scales of such platinum structures are in the range of a few micrometers to a few hundred nanometers. Reducing these length scales to further increase the TPB density is challenging with the above means. Here, we exploited the nucleation stage ...

No abstract

This report presents a demonstration and characterization of a nanotubular array of solid oxide fuel cells (SOFCs) made of one-end-closed hollow tube Ni/yttria-stabilized zirconia/Pt membrane electrode assemblies (MEAs). The tubular MEAs are nominally ∼5 μm long and have <500 nm outside diameter with total MEA thickness of nearly 50 nm. Open circuit voltages up to 660 mV (vs air) and power densities up to 1.3 μW cm(-2) were measured at 550 °C using H2 as fuel. The paper also introduces a fabrication methodology primarily based on a template process involving atomic layer deposition and electrodeposition for building the nanotubular MEA architecture as an important step toward achieving high surface area ultrathin SOFCs operating in the intermediate to low-temperature regime. A fabricated nanotubular SOFC theoretically attains a 20-fold increase in the effective surface, while projections indicate the possibility of achieving up to 40-fold.

Using atomic force microscopy (AFM) lithography and selfassembled monolayer (SAM), selective atomic layer deposition (ALD) of ZrO 2 was performed to fabricate nanostructures. SAM layer was used for a chemical mask for ZrO 2 ALD process and AFM lithography for a nano-scale patterning method. AFM anodic oxidation process was applied to create oxide patterns on ODTScoated silicon substrates. Subsequent HF etching locally removes oxide, exposing silicon layer underneath. After 100 cycles of ZrO 2 ALD process and an oxygen plasma etching, ZrO 2 ALD nanostructure of 4~7 nm in height and ~130 nm in line width were fabricated. A growth rate of 0.4~0.7 Å per cycle is estimated from the AFM scanning at each step, which is slightly less than the typical ALD growth rates of ZrO 2 .