Development of freestanding bifunctional air cathodes for rechargeable zinc-air batteries.

Zheng, Xiaoying (2024). Development of freestanding bifunctional air cathodes for rechargeable zinc-air batteries. Thèse. Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 242 p.

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Résumé

The limited fossil fuels and the increasingly serious environmental issues have necessitated the development of a clean and renewable energy storage and conversion device. It is today advanced that the development of free-standing (binderless) air cathode via direct growth of non-precious metal electrocatalysts onto the surface of the conductive collector would be the cutting-edge strategy to reduce the interfacial resistance, improve the mechanical stability, reduce the final weight and the cost manufacturing. Herein, the free-standing MnOx directly grown on the carbon substrates of carbon paper (CP), carbon nanotubes (CNTs) modified CP, carbon sphere chains (CSCs) modified CP, and their electrochemical functionalized substrates are proposed. With detailed electrochemical studies, the CNTs, CSCs, and their cost-effective surface functionalization combined with the MnOx offer a synergistic bifunctional effect toward oxygen reduction/evolution reactions (ORR/OER). The Zn-air batteries (ZABs) studies indicated high specific capacity, and stable voltage gaps along the galvanostatic charge-discharge (GCD) test suggesting the stability and good bifunctional electrocatalytic activities of these cathodes towards ORR/OER in a real ZAB device. Despite a bright future of MnO2 shown ORR/OER and ZAB performance, the intrinsic low electrical conductivity glooms its application in electrocatalytic reactions. The doping strategy is applied to equip our self-supported MnO2 with enhanced ORR/OER and ZAB performance. A class of self-supported MnO2 nanorods arrays on the abovementioned substrates doped with either cobalt or nickel cations are engineered through a simple hydrothermal method. The substitutional doping by Co or Ni which partly replaces the Mn ions in the [MnO6] octahedra brings about the Jahn-Teller distortion that exhibited enhanced catalytic performance for ORR and OER. With comprehensive investigations based on the electrodes with CP and functionalized CSCs substrates, an optimal concentration of 0.25 in the molar ratio Co/Mn or Ni/Mn is discovered based on the ORR/OER bifunctionality. Homemade rechargeable ZABs assembled with doped MnO2 deliver higher peak power density, higher specific capacity, lower charge voltage, lower charge/discharge voltage, and robust stability. As a proof-of-concept for handheld electronic applications, the ZABs with our free-standing MnOx as cathodes successfully functioned as a laboratory timer, light-emitting diode (LED) bulbs, a multimeter, and even the self-driven overall water-splitting system. The proposed strategy and results may pave the way for a rational design of hierarchical free-standing bifunctional electrocatalysts for ZABs, other metal-air batteries, and fuel cells.

Type de document:	Thèse Thèse
Directeur de mémoire/thèse:	Mohamedi, Mohamed
Mots-clés libres:	zinc-air batteries ; freestanding electrodes ; binderless hierarchical structure ; carbon nanotubes ; carbon sphere chains ; manganese oxides ; bifunctional oxygen electrocatalyst ; oxygen reduction reaction ; oxygen evolution reaction ; cobalt or nickel doping ; batteries zinc-air ; électrodes autoportantes ; structure hiérarchique sans liant ; nanotubes de carbone ; chaînes de sphères de carbone ; oxydes de manganèse ; électrocatalyseur bifonctionnel à oxygène ; réaction de réduction de l'oxygène ; réaction de dégagement d'oxygène ; dopage au cobalt ou au nickel
Centre:	Centre Énergie Matériaux Télécommunications
Date de dépôt:	28 nov. 2024 20:32
Dernière modification:	28 nov. 2024 20:32
URI:	https://espace.inrs.ca/id/eprint/16203

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