Engineering topics

Lu, Matthew Y.

Publications and source records attributed to Lu, Matthew Y..

3 records

DOE OSTI2021

Characteristics of Oxygen Electrode Supported Reversible Solid Oxide Cells

Oxygen-electrode-supported solid oxide cells (OESCs) have potential advantages over fuel-electrode-supported cells, including reduced fuel-electrode concentration polarization, better oxygen electrode current collection, and flexibility in the fuel electrode choice. However, there are serious drawbacks including the difficulty of co- firing the oxygen electrode and electrolyte, and oxygen electrode concentration polarization. This paper explores the characteristics of OESCs with La 0.8 Sr 0.2 MnO 3-δ -Zr 0.92 Y 0.16 O 2-δ (LSM-YSZ) electrode-support enhanced by SrTi 0.3 Fe 0.6 Co 0.1 O 3-δ (STFC) infiltration, thin YSZ electrolyte, and SrTi 0.3 Fe 0.7 O 3-δ (STF) fuel electrodes. Here, the STFC infiltration increases fuel cell maximum power density by > 1.5 times and electrolysis current density (at 1.3 V) by > 2 times. Cell performance in pure oxygen is compared to that in air, exploring a possible reversible solid oxide cell system configuration where oxygen produced during electrolysis is stored and subsequently used during fuel cell operation. The fuel cell maximum power density is increased from 0.88 W cm -2 in air to 1.37 W cm -2 in oxygen, with limiting current increased from 1.7 to >5.6 A cm -2 ; the electrolysis performance is essentially unchanged, probably because the electrode air becomes enriched with oxygen during electrolysis.

25 ENERGY STORAGE↗

DOE OSTI2020

Sm 0.5 Sr 0.5 CoO 3-δ Surface Modification of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ -Ce 0.9 Gd0.1 2-δ Composite Oxygen Electrodes for Solid Oxide Electrochemical Cells

La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3- δ -Ce 0.9 Gd 0.1 O 2- δ (LSCF-GDC) composite oxygen electrodes have been widely used in intermediate temperature (<700 °C) solid oxide cells, with composite usually providing better electrochemical performance than single-phase LSCF. However, LSCF-based electrodes are often observed to degrade over time due to Sr segregation. Here we present an impedance spectroscopy study comparing the degradation behaviors of LSCF-GDC and Sm 0.5 Sr 0.5 CoO 3- δ (SSC) infiltrated LSCF-GDC electrodes. The LSCF-GDC polarization resistance increases by ~5 times over ~1000 h at 650 °C. In contrast, the SSC-infiltrated electrode shows similar initial polarization resistance but much more stable performance. The impedance modeling results show that the improved stability is associated with the low frequency oxygen dissociative adsorption/desorption process. The results suggest that this adsorption/desorption process slows due to increased Sr segregation on LSCF over time, and that SSC does not degrade significantly due to Sr surface segregation.

Electrochemistry↗

DOE OSTI2020

Advanced oxygen-electrode-supported solid oxide electrochemical cells with Sr(Ti,Fe)O 3–δ -based fuel electrodes for electricity generation and hydrogen production

Sr(Ti 0.3 Fe 0.7 )O 3–δ (STF) and the associated exsolution electrodes Sr 0.95 (Ti 0.3 Fe 0.63 Ru 0.07 )O 3–δ (STFR), or Sr 0.95 (Ti 0.3 Fe 0.63 Ni 0.07 )O 3–δ (STFN) are alternatives to Ni-based cermet fuel electrodes for solid oxide electrochemical cells (SOCs). They can provide improved tolerance to redox cycling and fuel impurities, and may allow direct operation with hydrocarbon fuels. However, such perovskite-oxide-based electrodes present processing challenges for co-sintering with thin electrolytes to make fuel electrode supported SOCs. Thus, they have been mostly limited to electrolyte-supported SOCs. Here, we report the first example of the application of perovskite oxide fuel electrodes in novel oxygen electrode supported SOCs (OESCs) with thin YSZ electrolytes, and demonstrate their excellent performance. The OESCs have La 0.8 Sr 0.2 MnO 3–δ –Zr 0.92 Y 0.16 O 2–δ (LSM–YSZ) oxygen electrode-supports that are enhanced via infiltration of SrTi 0.3 Fe 0.6 Co 0.1 O 3–δ , while the fuel electrodes are either Ni-YSZ, STF, STFN, or STFR. Fuel cell power density as high as 1.12 W cm –2 is obtained at 0.7 V and 800 °C in humidified hydrogen and air with the STFR electrode, 60% higher than the same cell made with a Ni-YSZ electrode. Electrolysis current density as high as –1.72 A cm –2 is obtained at 1.3 V and 800 °C in 50% H 2 O to 50% H 2 mode; the STFR cell yields a value 72% higher than the same cell made with a Ni-YSZ electrode, and competitive with the widely used conventional Ni-YSZ-supported cells. The high performance is due in part to the low resistance of the thin YSZ electrolyte, and also to the low fuel electrode polarization resistance, which decreases with fuel electrode in the order: Ni-YSZ > STF > STFN > STFR. The high performance of the latter two electrodes is due to exsolution of catalytic metal nanoparticles; the results are discussed in terms of the microstructure and properties of each electrode material, and surface oxygen exchange resistance values are obtained over a range of conditions for STF, STFN, and STFN. Furthermore, the STF fuel electrodes also provide good stability during redox cycling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗