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Park, Beom-Kyeong

Publications and source records attributed to Park, Beom-Kyeong.

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Effect of Nanoscale Ce 0.8 Gd 0.2 O 2–δ Infiltrant and Steam Content on Ni–(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 Fuel Electrode Degradation during High-Temperature Electrolysis

Studies of Ni–yttria-stabilized zirconia (YSZ) fuel electrode degradation mechanisms in solid oxide electrolysis cells (SOECs) are complicated by the different possible Ni–YSZ microstructures and compositions, and the variations in the H 2 /H 2 O ratio encountered in an electrolysis stack. Here, in this study, we describe a life testing scheme aimed at providing survey results on degradation as a function of the H 2 O–H 2 composition, with life tests carried out at five different steam contents from 90% to 10%. A Ni–YSZ-supported symmetric cell geometry is employed both with and without infiltrated nanoscale gadolinia-doped ceria (GDC). Impedance spectroscopy is utilized to observe changes in electrochemical characteristics during the life test, and a transmission-line-based equivalent circuit is used to model the data. Post-test electrode microstructures were observed. The results suggest that the GDC infiltrant reduces the electrode polarization resistance and provides more stable electrode polarization over a range of conditions.

08 HYDROGEN↗
DOE OSTI2020

On the role of the zirconia/ceria interface in the degradation of solid oxide electrolysis cells

Gd-doped Ceria (GDC) barrier layers are widely used in solid oxide electrolysis cells to prevent reactions between the Y-stabilized Zirconia (YSZ) electrolyte and oxygen electrode. In some cases, electrolysis operation causes fracture near the GDC/YSZ interface. Here, we explain this effect using a numerical calculation, showing that a peak oxygen pressure is observed near the GDC/YSZ interface during electrolysis operation. Moreover, GDC/YSZ interdiffusion and possible zirconate phase formation occurring during electrode firing yield a low oxygen ion conductivity region that introduces a much higher peak oxygen partial pressure at the interdiffusion layer/YSZ interface, thereby exacerbating degradation. The results indicate that the peak pressure can be reduced and, thereby, damage can be mitigated by altering processing in order to minimize interdiffusion, decreasing the GDC layer thickness, and reducing oxygen electrode polarization resistance or altering electrolyte transport properties, e.g., changing the Gd doping level of GDC to increase the oxygen vacancy diffusivity.

Physics↗
DOE OSTI2020

Tuning electrochemical and transport processes to achieve extreme performance and efficiency in solid oxide cells

Solid oxide cells (SOCs) have important applications as fuel cells and electrolyzers. The application for storage of renewable electricity is also becoming increasingly relevant; however, it is difficult to meet stringent area-specific resistance (ASR) and long-term stability targets needed to achieve required efficiency and cost. Here we show a new SOC that utilizes a very thin Gd-doped ceria (GDC)/yttria-stabilized zirconia (YSZ) bi-layer electrolyte, Ni–YSZ cell support with enhanced porosity, and electrode surface modification using PrO x and GDC nanocatalysts to achieve unprecedented low ASR values < 0.1 Ω cm 2 , fuel cell power density ~3 W cm –2 , and electrolysis current density ~4 A cm –2 at 800 °C. Besides this exceptionally high performance, fuel cell and electrolysis life tests suggest very promising stability in fuel cell and steam electrolysis modes. Furthermore, electrochemical impedance spectroscopy analysis done using a novel impedance subtraction method shows how rate-limiting electrode processes are impacted by the new SOC materials and design.

25 ENERGY STORAGE↗
DOE OSTI2020

Boosting solid oxide fuel cell performance via electrolyte thickness reduction and cathode infiltration

Increasing the power density and reducing the operating temperature of solid oxide fuel cells (SOFCs) is important for improving commercial viability. Here we discuss two strategies for achieving such improvements in Ni–YSZ supported SOFCs – electrolyte thickness reduction and cathode infiltration. Microstructural and electrochemical results are presented showing the effect of reducing YSZ/GDC electrolyte thickness from 8 to 2.5 μm, and the effect of PrO x infiltration into the LSCF–GDC cathode. Both of these measures are effective, particularly at lower temperatures, leading to an increase in the maximum power density at 650 °C from 0.4 to 0.95 W cm –2 , for example. Electrochemical impedance spectroscopy utilizing subtractive analysis shows that PrO x enhances the cathode charge transfer process. Reducing the electrolyte thickness reduces not only the cell ohmic resistance but also the electrode polarization resistance. Furthermore, the latter effect appears to be an artifact associated with a slight increase in the steam partial pressure at the anode due to minor gas leakage across the thinner electrolyte.

25 ENERGY STORAGE↗
DOE OSTI2020

Enhancement of Ni–(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 fuel electrode performance by infiltration of Ce 0.8 Gd 0.2 O 2–δ nanoparticles

This paper addresses the use of Ce 0.8 Gd 0.2 O 2–δ (GDC) infiltration into the Ni–(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 (YSZ) fuel electrode of solid oxide cells (SOCs) for improving their electrochemical performance in fuel cell and electrolysis operation. Although doped ceria infiltration into Ni–YSZ has recently been shown to improve the electrode performance and stability, the mechanisms defining how GDC impacts electrochemical characteristics are not fully delineated. Furthermore, the electrochemical characteristics have not yet been determined over the full range of conditions normally encountered in fuel cell and electrolysis operation. Here we present a study of both symmetric and full cells aimed at understanding the electrochemical mechanisms of GDC-modified Ni–YSZ over a wide range of fuel compositions and temperatures. Single-step GDC infiltration at an appropriate loading substantially reduced the polarization resistance of Ni–YSZ electrodes in electrolyte-supported cells, as measured using electrochemical impedance spectroscopy (EIS) at various temperatures (600–800 °C) in a range of H 2 O–H 2 mixtures (3–90 vol% H 2 O). Fuel-electrode-supported cells had significant concentration polarization due to the thick Ni–YSZ supports. Here, a distribution of relaxation times approach is used to develop a physically-based electrochemical model; the results show that GDC reduces the reaction resistance associated with three-phase boundaries, but also appears to improve oxygen transport in the electrode. Increasing the H 2 O fraction in the H 2 –H 2 O fuel mixture reduced both the three-phase boundary resistance and the gas diffusion resistance for Ni–YSZ; with GDC infiltration, the electrode resistance showed less variation with fuel composition. GDC infiltration improved the performance of fuel-electrode-supported full cells, which yielded a maximum power density of 2.28 W cm –2 in fuel cell mode and an electrolysis current density at 1.3 V of 2.22 A cm –2 , both at 800°C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗