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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/221059
High Entropy Materials as Air Cathodes for Robust Zinc-Air Batteries
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[eng] This thesis focuses on the development of high-entropy materials (HEMs) as advanced bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The study systematically investigates the synthesis methods, structural properties, and catalytic performance of these materials, with particular emphasis on their application in zinc-air batteries (ZABs). Through the incorporation of transition metals and experiencing surface reconstruction processes, these materials exhibit remarkable catalytic efficiencies and stability. Density functional theory (DFT) calculations provide further insights into the active sites and mechanisms driving the enhanced catalytic activity. This research highlights the potential of high entropy alloys (HEAs) and high-entropy phosphides (HEPs) as next-generation catalysts, paving the way for future advancements in energy storage and conversion technologies.
In Chapter 2, I detail the development a low-temperature colloidal method to synthesize CrMnFeCoNi and CuMnFeCoNi HEAs, along with quaternary and ternary alloys. CrMnFeCoNi displays superior bifunctional catalytic performance for both OER and ORR, outperforming CuMnFeCoNi, quaternary alloys, and commercial catalysts like RuO2 and Pt/C. DFT calculations reveal that the incorporation of Cr into the MnFeCoNi matrix lowered the energy barriers for OER and optimized ORR intermediate steps. This material exhibits high power density, specific capacity, and excellent long-term cycling stability when applied as a bifunctional catalyst in ZABs, underscoring its potential for energy storage applications. This work was published in Energy Storage Materials in 2023.
Chapter 3 presents the synthesis of FeCoNiMoW HEA by incorporating 4d Mo and 5d W into a 3d FeCoNi matrix using a low-temperature solution-based method. The resulting alloy demonstrates a highly distorted lattice and strong electronic coupling effects. The FeCoNiMoW HEA exhibits excellent catalytic performance for OER with low overpotentials and great bifunctional properties, surpassing commercial catalysts like Pt/C and RuO2. DFT calculations identify Ni as the active site for OER, with Mo and W enhancing oxygen intermediate interactions. The FeCoNiMoW-based ZABs show high power density, specific capacity, and exceptional long-term stability, even
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in flexible applications, making them a promising candidate for wearable energy devices. This work was published in Advanced Materials in 2023.
In Chapter 4, I detail the synthesis of FeCoNiPdWP HEPs via a mild colloidal method, resulting in a homogeneous nanostructure. These HEPs demonstrate exceptional bifunctional catalytic performance for both OER and ORR, with a low overpotential of 227 mV for OER and a half-wave potential of 0.81 V for ORR. The outstanding OER performance is attributed to the reconstructed FeCoNiPdWOOH surface, enriched with high-oxidation-state Fe, Co, and Ni. Pd facilitates OH⁻ adsorption, while W modulates the electronic structure for better oxygen intermediate adsorption. For ORR, surface reconstruction into FeCoNiPdWPOH further enhances performance, with Pd and W maintaining their phosphide environments and Pd as the main active site for ORR. The small energy gap between OER and ORR enables FeCoNiPdWP HEPs to achieve over 700 h of stable operation in ZABs, showcasing their potential for long-term and highly efficient bifunctional catalysis. This work was published in Energy & Environmental Science in 2024.
The main conclusions of this thesis and some perspectives for future work are presented in the last.
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HE, Ren. High Entropy Materials as Air Cathodes for Robust Zinc-Air Batteries. [consulta: 30 de novembre de 2025]. [Disponible a: https://hdl.handle.net/2445/221059]