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We have fabricated thin film-solid oxide fuel cells (TF-SOFCs) with tri-layer electrolytes, which are composed of YSZ deposited by sputtering, YSZ deposited by plasma enhanced atomic layer deposition (PEALD), and GDC deposited by sputtering. Then, we have investigated the effects of the PEALD YSZ on the GDC layer and the whole cell. Open circuit voltages (OCVs) and peak power densities of the cells kept being enhanced as the thickness of the PEALD YSZ layer increases. The 1000 cycle of PEALD YSZ deposited TF-SOFC exhibited 214 mW/cm2 of peak power density, while TF-SOFC without PEALD YSZ inter-layer showed 124 mW/cm2, almost half of that of the 1000 cycle sample. FE-SEM images and AFM analysis of the top surface of GDC electrolytes sustain this phenomenon. As the PEALD YSZ inter-layer thickness increases, the top surface of GDC electrolyte become rough, with pin-holes disappeared, and the grain size of GDC electrolyte grew smaller. As a result, the improved quality of the electrolytes enhanced OCV and smaller grain size of the electrolytes caused better catalytic activity on the electrolyte-cathode interface, leading to lower faradaic impedances in electrochemical impedance spectroscopy (EIS).

The effect of nano-pinholes in the ceramic electrolyte (yttria-stabilized zirconia) on the performance of a thin-film solid oxide fuel cell (SOFC) is investigated. As a result, the open-circuit voltage of the thin-film SOFC was not severely affected by the existence and the size of a pinhole. However, the pinhole induced a critical electrical shortage between the anode and cathode if the cathode was deposited onto the pinhole. Thus, a nano-sized pinhole does not significantly induce fuel crossover or critically reduce the performance. It could, however, reduce the performance significantly during the common fabrication step, i.e. deposition of thin-film cathode on an electrolyte, of a thin-film SOFC, especially for larger pinholes.

Performance of thin film solid oxide fuel cells (TF-SOFCs) were improved by inserting plasma enhanced atomic layer deposition (PEALD) of yttira-stabilized zirconia (YSZ) interlayers. By controlling the ratio between Y2O3 and ZrO2 in YSZ deposition supercycles, Y2O3 mol.% in YSZ films were changed. High Y2O3 contained PEALD YSZ interlayered cell showed higher maximum power density (123.6 mW/cm2 at 500 °C, 286.1 mW/cm2 at 550 °C) and smaller polarization resistance compared with reference Y2O3 concentrated PEALD YSZ interlayer cell. (108.5 mW/cm2 at 500 °C, 181.1 mW/cm2 at 550 °C) Exchange current densities of TF-SOFCs at 500 °C also improved ~ 59.3% at high Y2O3 concentrated PEALD YSZ interlayer cells. These phenomena caused by high density of oxygen vacancies in high Y2O3 concentrated PEALD YSZ interlayer, which helps oxygen incorporation reactions at cathode-interlayer interface. Therefore, cathodic polarization loss related with oxygen reduction reactions was decreased, and then, performance and exchange current density were improved. Results of this study imply that insertion of simple PEALD YSZ interlayer at cathode-electrolyte interface efficiently improves performance and electrochemical characteristics of TF-SOFCs.

Metal/NiO-Smarium-doped ceria (SDC) nano-composite thin film anodes were deposited on anodic aluminum oxide by co-sputtering to enhance the in-plane current-collecting ability and investigated by varying the composition of metal materials (Pt and Au). Full fuel cells with these nano-composites were fabricated and tested at 500 °C. Columnar anodes with a sponge structure were fabricated by varying the DC sputtering source power and they were thermally stable at the operating temperature. By adding metal material, the ohmic resistance, including the current collecting resistance, was drastically reduced and the polarization resistance also decreased. The nano-composite electrode with a Pt content of 61 at% showed the highest performance, which is a maximum power density of 212.5 mW/cm2 at 500 °C. In addition, Au was considered to reduce the current collecting resistance and the corresponding power density was 3 times higher than that with the NiO-SDC anode.

A thin film solid oxide fuel cell (TF-SOFC) with a Ni anode on a nanoporous anodic aluminum oxide substrate was demonstrated. In our experiments, Ni was used as an anode material, while a very small amount of Pt was used as a cathode material, which reduced the thickness of the thin film cathode to 65 nm. In addition, a plasma-enhanced atomic layer deposition method was used to prepare a yttria-stabilized zirconia electrolyte. The open circuit voltage and the peak power density of the as-fabricated fuel cells, both of which were measured at 500 °C, were 1.04 V and 150 mW/cm2, respectively.

In this study, we investigate the possibility of using Ni-based anodes as alternatives to the Pt-based anodes for thin-film solid oxide fuel cells (SOFCs) operating at low temperatures. Anodes, electrolytes, and cathodes are sequentially sputtered onto a nanoporous substrate. The pure Ni anodes with modified nanostructures exhibit comparable performance as that of the optimized Pt anodes. Furthermore, a Ni/Ni-YSZ bilayer anode fabricated via a co-sputtering method exhibits approximately 37% higher peak power density than does the optimized Pt anode at 500 °C, demonstrating that noble metal anodes can be replaced by Ni-based anodes in low-temperature SOFCs by optimizing the anode nanostructure.

Nickel-Samaria Doped Ceria (Ni-SDC) cermet anodic thin films of about 500 nm were prepared on Scandia Stabilized Zirconia (ScSZ) electrolyte supports via reactive radio frequency (RF) sputtering. Anode deposition was done at room temperature, and the background sputtering gas was a reactive mixture of Ar : O2/80 : 20. The oxide conducting fuel cell configuration was completed by screen printing of lanthanum strontium manganite (LSM/YSZ) cathodes on the other side of the ScSZ supports. High resolution transmission electron microscopy (HR-TEM) of the cermet anode revealed an arranged nanostructure, with patterned ceria enclosing the nickel molecules in porous media. These highly ordered anodes were tested under (i) H2 and (ii) a product fuel of CO2 electro-reduced via industrial waste carbon (IWC). IWC fuel performance matched the H2 fuel performance in terms of peak power density and longevity, with an added lower fuel cost advantage. HR-TEM and scanning electron microscope (SEM) 2D images were utilized to simulate the reaction kinetics of the nanostructured porous thin film cermet anode. The reported high electrochemical performance was proved to result from the high density of triple-phase boundaries, arranged nanostructure and high contiguity of the special design of the nano-anodes. Experimental and simulation results were coherent with each other, especially for IWC operated SOFCs working at or above 700 °C.

Nanostructured Ni thin films, with high porosity, are fabricated by DC sputtering on an anodic aluminum oxide template as an active anode for low-temperature solid oxide fuel cells with a target operating temperature of 500 °C. To maximize the electrode performance, we control their effective electrical conductivity and microstructure by varying the sputtering parameters (e.g., the deposition pressure and time) and investigate the gas permeability, sinterability, as well as the ohmic and polarization resistances by a range of analysis techniques, in this case SEM, TEM, mass spectrometry, the four-point probe method and AC impedance spectroscopy. We observe that the thicker the Ni film, the higher the effective electrical conductivity and the lower the sheet resistance, while the thinner the film, the better the gas permeability and electrochemical activity for H2 electro-oxidation. These tradeoffs are quantitatively computed for cell dimensions and area specific resistances, thus suggesting an optimal design for affordable and high-performance electrodes.

We prepared nickel-samaria-doped-ceria cermet anodes for intermediate temperature solid oxide fuel cells, by using two different background sputtering gases. One is a reactive mixture gas of pure argon and oxygen (Ar/O2:80/20), and other is non-reactive pure argon gas. For all cells, a 150 μm fully stabilized scandia-stabilized-zirconia pellet was used as an electrolyte support. Lanthanum strontium manganite ink was screen-printed on the electrolyte support to act as a cathode. Initial results showed that the anodes produced by non-reactive background sputtering gas, outperformed the anodes produced by reactive mixture background gas in all categories of performance and also showed lesser agglomeration with time.

We report the advantages of atomic layer deposition (ALD) for the fabrication of yttria-stabilized zirconia (YSZ) electrolyte. The reactivity and stability of anodic aluminum oxide (AAO)-based thin-film solid oxide fuel cells (SOFCs) are improved by applying ALD YSZ electrolyte. The fuel cell fabricated by ALD shows a peak power density of 154.6 mW cm −2 at 450 °C, whereas the fuel cell fabricated by sputtering demonstrates a peak power density of 66.2 mW cm −2 . The amorphous and nanogranular microstructure of the ALD YSZ film is ascribed for a significant improvement in the cathodic reactivity of the AAO-based thin-film fuel cells. Moreover, the smooth and uniform surface of the ALD YSZ electrolytes mitigates the agglomeration of the Pt cathode layer, and thus the thermal stability of the thin-film fuel cell is remarkably improved at 450 °C.

Thin film solid oxide fuel cells with nickel oxide–gadolinia doped ceria anodes deposited by sputtering were operated at 500 °C. The fuel cells each have 750 nm–yttria-stabilized zirconia electrolytes and 200 nm–platinum cathodes. The thicknesses of the anodes are 240 nm, 320 nm, and 400 nm. The cell with the 320-nm-thick anode showed the highest maximum power density among all cells. Through electrochemical impedance spectroscopy, the anodic activation resistance and the ohmic resistance were calculated. The anodic activation loss decreased with an increase in the anode thickness. Therefore, the cell with the 400-nm-thick anode showed the lowest activation polarization resistance. Additionally, the ohmic resistance, the sum of various electronic/ionic resistances, was lowest when using the 320-nm-thick anode. The electronic resistance and the ionic resistance of the anode were found to exist in a trade-off relationship owing to the current-collecting method of the anode.

Thin film solid oxide fuel cells (SOFCs) with Pt anode, yttria-stabilized zirconia (YSZ) electrolyte, and Pt cathode were fabricated based on nano-porous substrate. Pt and YSZ were deposited using sputter and plasma-enhanced atomic layer deposition (PEALD), respectively. Here, two types of Pt anode, i.e., dense and porous, were prepared to compare the performances of the fuel cells. The performance of the fuel cell with the porous Pt anode showed higher peak power density (194 mW/cm 2 ) than that with the dense Pt anode (178 mW/cm 2 ) at 500 °C. Through the analyses via scanning electron microscopy and electrochemical impedance spectroscopy (EIS), it was found that the increase of the performance was attributed to the enhanced supply of the hydrogen into the porous anode and resulting enhancement of charge transfer and mass transport. In the EIS results, the anodic charge transfer resistance of the fuel cell with the dense Pt anode was higher than that of the porous Pt anode, even though the porous Pt anode is thicker than the dense Pt anode. The result from a high-resolution transmission electron microscopy and electron-dispersive spectroscopy images showed that anodic pores were slightly filled with YSZ due to the low conformality of PEALD, resulting in the additional formation of triple phase boundaries.

In this paper, we present a simple and novel approach for stabilizing a porous metal-based nanostructure through atomic layer deposition in which ultra-thin tin oxide (SnO2) coats platinum (Pt) film. After heating the ultra-thin tin oxide-coated Pt samples at 300°C and 500°C and observing the in situ sheet resistance variations of Pt for 20 hours, we found that the ultra-thin tin oxide coating suppresses metal agglomeration. The thermal stability of ultra-thin tin oxide-coated Pt was greater than that of pure Pt, even at 300°C and 500°C. More interestingly, the ultra-thin tin oxide coating was found to maintain the morphology of its underlying porous Pt at test temperatures of 300°C and 500°C.

In this study, influence of carbon impurities on characteristics of ALD-YSZ films is systematically investigated. Carbon concentration in ALD-YSZ films was controlled by changing Y 2 O 3 ratio in YSZ super cycle. To examine electrochemical characteristics of ALD-YSZ films, nano-porous templates based thin film solid oxide fuel cells (TF-SOFCs) were fabricated with ALD-YSZ thin film electrolyte and examined at 500 °C. Open circuit voltages (OCVs) of TF-SOFCs with ALD-YSZ were clearly dependent on carbon contaminations. High carbon concentration caused leakage current through internal short circuit, and then, OCVs of TF-SOFCs were decreased. Post-processing of ALD-YSZ thin film electrolyte improved OCVs of TF-SOFCs.

We investigated the microstructures and electrical properties of thermally stable ZrO2-coated Ag nanowires (NWs) under high temperatures of up to 600 °C. Although the ZrO2-coating layers on the Ag NWs were sub 1 nm (

To study the geometrical scale dependency of thin film solid oxide fuel cells (SOFCs), we fabricated three thin films SOFCs which have the same cross-sectional structure but different electrode areas of 1 mm2, 4 mm2 and 9 mm2. Since the activation and ohmic losses of SOFCs depend on their active region, we examined the variations of the power density of the cells with a Pt/YSZ/Pt structure and simulated the power density variations using the COMSOL software package.

Due to its high surface area and catalytic activity, the nanostructure of platinum significantly enhances the electrochemical reactions of electrodes. However, the inherently poor thermomechanical stability of the nanostructure has been a critical issue. This study suggests a simple method of using a Pd layer deposited by sputtering to enhance the stability of the 20 nm thick nanoporous Pt. The microstructural analysis reveals that the Pd films are partially oxidized at operating temperature to nano-polycrystalline Pd formed around Pt particles and inhibiting the mobility of the Pt grains. By preserving the Pt nanostructure, the degradation rate of the Pt–Pd cathode structure is 10 times lower than that of the Pt cathode.

Gadolinium-doped ceria (GDC) deposited by radio frequency magnetron sputtering is utilized as the anode interlayer for low-temperature solid oxide fuel cells (LT-SOFCs) with a nanothin yttria-stabilized zirconia (YSZ) electrolyte and Ni/Pt electrodes. When the thickness ratio of YSZ electrolyte versus 100 nm GDC anode interlayer is at or below 1.5, the electrochemical performance of the LT-SOFC is severely poor due to the microstructural instability of the GDC anode interlayer under high-temperature reducing atmospheric conditions. At 500 °C, the peak power density of the LT-SOFC with a Ni anode and a 20 nm GDC anode interlayer is ~ 30% higher than that without the GDC anode interlayer due to faster reaction kinetics on the anode side.

Yttria-stabilized zirconia (YSZ) thin film electrolyte deposited by plasma enhanced atomic layer deposition (PEALD) was investigated. PEALD YSZ-based bi-layered thin film electrolyte was employed for thin film solid oxide fuel cells on nanoporous anodic aluminum oxide substrates, whose electrochemical performance was compared to the cell with sputtered YSZ-based electrolyte. The cell with PEALD YSZ electrolyte showed higher open circuit voltage (OCV) of 1.0 V and peak power density of 182 mW cm(-2) at 450 °C compared to the one with sputtered YSZ electrolyte(0.88 V(OCV), 70 mW cm(-2)(peak power density)). High OCV and high power density of the cell with PEALD YSZ-based electrolyte is due to the reduction in ohmic and activation losses as well as the gas and electrical current tightness.

Thin film solid oxide fuel cells (thin film SOFCs) were introduced to reduce the high operating temperature of traditional SOFCs. By employing thin film techniques such as sputtering, atomic layer deposition, and pulsed laser deposition, less than 1 μm-thick electrolytes have been successfully fabricated and functioned properly. Through these thin film electrolytes, the low ionic conductivity of the electrolyte materials at reduced temperature is compensated by the shortened travel length of the oxygen ions. However, low temperature also leads the poor electrode activity, and this lowered activity has not been fully overcome. In this study, we investigated various types of Ni-based cermet films to gain better electrode activity. The cermet films were fabricated by magnetron sputtering. For ion-conducting materials, yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ) were used. These ion-conducting materials were co-sputtered with Ni. The sputtering power of each material was varied for changing Ni contents of the films. To obtain the Ni contents, we utilized X-ray photoelectron spectroscopy (XPS). Four-point probe measurement was also conducted to verify the degree of Ni percolation of the films. In addition, the surface and cross-sectional images of the films were observed to investigate the microstructure and porosity. For analyzing the electrochemical performance of the co-sputtered cermet films at reduced temperature, we fabricated several experimental SOFCs. On the one side of the solid electrolyte pellet, the thin cermet anode was deposited, while thin Pt cathode was deposited on the other side of the pellet. Then, the experimental SOFCs were operated at below 500 oC. During the operation, the j-V characteristics and electrochemical impedance spectroscopy (EIS) of the cells were studied. The thermal stability of the cells was also characterized by potentiostatic measurement and the measured data were compared to the cell with pure Ni anode.

Oxygen has been introduced into reactively ion-plated TiN to determine its effect on the film microstructure, resistivity and electrochemical properties. Oxygen levels incorporated into the films varied from 5 a/o to a maximum of 35 a/o as indicated by Auger electron spectroscopy (AES). While no oxide phases were revealed by X-ray diffraction (XRD), results indicate increasing degrees of microcrystallinity with increasing bulk oxygen content. From electrochemical testing, films containing higher oxygen content appeared to have greater chemical stability; however, four-point probe analysis indicates increasing resistivity and the onset of insulating properties as the oxygen content in the films increases above 30 a/o.

Titanium nitride (TiN) thin film coatings were reactively ion plated onto Pyrex ® glass and aluminum alloy 6061-T6 substrates while systematically varying the r.f. power density to evaluate its effect on the physical properties of the coating. X-ray diffraction, scanning electron microscopy, four-point probe resistivity and potentiodynamic polarization analysis techniques were used to evaluate the TiN coating crystal structure, morphology, resistivity and corrosion behavior. TiN coating properties were found to be strongly dependent on the r.f. power density up to approximately 1.5W cm -2 . Below 1.5W cm -2 , increasing r.f. power density resulted in improved electrochemical and resistivity properties. Above 1.5W cm -2 , many of the coating properties became independent of the r.f. power density. Correlations between the microstructures, properties and processing parameters are discussed.