Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Building and Real Estate | en_US |
| dc.contributor.advisor | Ni, Meng (BRE) | en_US |
| dc.creator | Chen, Xi | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/14038 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Efficient and durable air electrodes for reversible protonic ceramic electrochemical cells | en_US |
| dcterms.abstract | Reversible protonic ceramic electrochemical cells (R-PCECs) hold great potential as an energy conversion and storage device. However, its electrochemical performance at reduced operating temperatures is hindered by sluggish and unstable oxygen reduction/evolution reactions (ORR/OER) at conventional air electrodes. To overcome this limitation, this thesis identified multiple strategies integrating bulk anion substitution, surface nanoparticles design, and one-pot bulk-phase self-assembly to develop high-performance triple-conducting (H+/O2-/e-) nanocomposite air electrodes with excellent stability. | en_US |
| dcterms.abstract | First, anion engineering is applied to altering the oxygen sites of sublattice in Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF). The results indicate that the electronegative fluorine substitution weakens metal-oxygen bonds and enhances proton uptake. Consequently, the optimized Ba0.5Sr0.5Co0.8Fe0.2O2.9-σF0.1 air electrode demonstrates accelerated surface oxygen exchange and bulk H+/O2- transport, leading to a ~70% reduction in area-specific resistance compared to pristine BSCF. | en_US |
| dcterms.abstract | Building on the first work’s foundation, a dual bulk-surface modification strategy is successfully implemented through in situ growth of nanoscale catalysts on the surface of fluorine-engineered perovskite oxides. As a result, the Ba(Co0.4Fe0.4Zr0.1Y0.1)0.95Ni0.05F0.1O2.9-δ nanocomposite air electrode exhibits a peak power density of 996 mW·cm-2 at 650 °C—60% higher than conventional electrodes—along with stable reversibility over 100 hours. | en_US |
| dcterms.abstract | Moreover, to resolve persistent challenges in steam resistance and thermomechanical compatibly, a Co/Sr-free dual-phase perovskite oxide, Ba(Zr0.1Ce0.7Y0.1Yb0.1)0.4Fe0.6F0.1O2.9-δ (BZCYYFF), is rational designed via one-pot self-assembly method. This design integrates a proton-conductive Ce-rich phase (P-BZCYYFF) with triple-conducting Fe-rich domains (M-BZCYYFF), establishing continuous proton transport pathways while eliminating phase segregation risks. Additionally, fluorine anion doping further weakens metal-oxygen bonds in both phases, thus enhancing ionic mobility without catalytic compromise. The final BZCYYFF electrode achieves an ultra-low ASR of 0.33 Ω·cm² at 550 °C, coupled with a peak power density of 0.494 W·cm⁻² in fuel cell mode and an exceptional electrolysis current density of 0.649 A·cm⁻² (electrolysis voltage of 1.3 V) at 550 °C. Long-term operation under 10% humidified air for over 160 hours and the 18 cycles spanning 180 hours demonstrates negligible degradation, further underscoring its unmatched durability. | en_US |
| dcterms.abstract | In conclusion, by harmonizing triple conductivity, hydration resistance, and thermal compatibility, this work establishes a materials design paradigm for robust R-PCEC air electrodes, advancing their viability for energy storage and hydrogen economy applications. | en_US |
| dcterms.extent | xviii, 145 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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