2023 Fiscal Year Research-status Report
Development of efficient low-cost SOFC/SOEC protonic cathodes for reliable energy distribution
| Project/Area Number |
19K05672
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| Research Institution | Kyushu University |
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Principal Investigator |
Kwati Leonard 九州大学, カーボンニュートラル・エネルギー国際研究所, 准教授 (70734391)
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| Project Period (FY) |
2019-04-01 – 2025-03-31
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| Keywords | Protonic defects / ionic transport / Triple conducting / Fuel cell / Catalytic activity / Electrolysis / proton kinetics / hydration |
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| Outline of Annual Research Achievements |
Solid-oxide fuel cells and electrolyzers that conduct protons are promising green energy conversion and storage technologies suited for low to intermediate-temperature regimes (300 -600 oC). However, their commercial viability has been hindered, in part, by the positrode’s kinetics and effective catalytic activity toward oxygen reduction and evolution reactions (ORR/OER).
The origin of catalytic activity in LnCo0.5Ni0.5O3-δ (Ln=La, Pr and Nd) perovskites "positrodes" (positive electrode) by low energy-ion scattering (LEIS) and DFT studies were investigated. The results reveal that La, Pr, and Pr cations dominate the outer atomic layer, with profound implications for catalytic activity. On the other hand, first principle calculations performed using the plane-wave DFT method and hybrid HSE06 functional suggest that the catalytic activity and electronic properties depend on the valence shell structure of the Ln-site cation and their redox properties.
non-stoichiometric A-site defects were introduced into PrxCo0.5Ni0.5O3-δ oxides (x = 1, 0.95, 0.9) to tune their mixed conduction properties. Pr deficiency can alter the charge compensation mechanism, leading to additional oxygen vacancies, subsequently translating to enhanced protonic fuel cells and electrolysis performance. Pr0.95Co0.5Ni0.5O3-δ:BaZr0.16Ce0.64Y0.1Yb0.1O3-δ (ratio 80:20) air electrodes show the lowest polarization resistance (Rp) of ~0.22 cm-2 (at 600 °C), determined from fuel cell mode of operation.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Using some of the materials characterized above specifically Pr0.95Co0.5Ni0.5O3-δ:BaZr0.16Ce0.64Y0.1Yb0.1O3-δ (ratio 80:20) as the air electrode on my half-cell demonstrates remarkable capabilities and endurance within the 450-600°C temperature range, achieving a peak power density of 1.13 W cm-2 at 600 oC in the fuel cell mode and a high current density of 1.5 A cm-2 at 1.3 V in the electrolysis mode. Suggesting a better understanding of the air electrode materials
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| Strategy for Future Research Activity |
In other to fully understand the underlying principles of ionic transport in protonic oxides, additional spectroscopic studies are required to reveal their electronic properties, the spin state of constituent cations, their coordination, and changes while the oxide is being exposed to water vapor. Going forward, I will focus on using X-ray absorption spectroscopy (XAS) realized in both near-edge and extended ranges (if possible) to further understand the dependence between elemental compositions and their electron configuration. Detailed near-edge feature analysis will be performed to obtain information on the oxidation state and changes in the electronic structure of all elements upon hydration.
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| Causes of Carryover |
The present amount is what was left over and carried forward due to project extension and will be used for research expenditure, beam line
payment.
The purchase of items such as, high-grade chemical reagents for material synthesis, High purity gases, platinum lead wires, equipment
maintenance
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