Restriction lift date: 2027-12-31
Bifunctional nickel-based electrodes for electrochemical energy storage and low-grade heat harvesting
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Date
2025-12-01
Authors
Palanisamy, Rupa Ranjani
Journal Title
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Publisher
University College Cork
Published Version
Abstract
The increasing demand for sustainable energy technologies underscores the need to develop materials that enable both efficient energy storage and the harvesting of low-grade heat. Electrochemical supercapacitors offer rapid charge storage and long operating lifetimes, while thermoelectrochemical cell (TEC) provide a route to convert low-grade waste heat into usable electrical energy. Although these two systems operate through different mechanisms and are not integrated into a single device, identifying electrode materials that can function effectively in both applications offers significant advantages. The bifunctional electrode demonstrates good performance in both systems because optimizing the synthesis parameters and material composition enhances flexibility in their application and enables a deeper understanding of the structure-property-performance relationships. This thesis investigates the controlled growth and electrochemical behaviour of nickel based nanostructured electrodes that are examined independently in asymmetric supercapacitors and TEC. Chapter I provides an overview of the fundamental principles governing energy storage in supercapacitors and thermal to electrical energy conversion in TEC. It outlines key performance considerations such as charge transport, redox activity and long-term structural stability, and introduces the motivation for exploring nickel based layered and chalcogenide systems as candidates for bi-functional use. Chapter II examines the synthesis of nickel-based selenide nanostructures supported on a conductive substrate. The chapter focuses on how composition, morphology and substrate interaction influence redox behaviour and ion accessibility. The electrodes are evaluated first in asymmetric supercapacitor configurations to understand their charge storage characteristics. Separately, the same electrode composition is examined in TEC to study its ability to generate an electrical potential from a temperature gradient. The chapter establishes how structural and compositional factors contribute to performance in these two distinct electrochemical environments. Chapter III shifts focus toward a more sustainable material design by reducing cobalt content and introducing aluminium to form nickel cobalt aluminium layered double hydroxide microstructures directly grown on nickel foam. This chapter highlights how the layered structure, sheet thickness and scaffold interface influence ion diffusion, redox reversibility and mechanical durability under prolonged cycling. The electrodes are assessed independently in asymmetric supercapacitors and TEC, demonstrating that careful control of composition and morphology contributes to storage and thermal conversion performance, without requiring any integration of the two device systems.
Chapter IV progresses to cobalt free compositions by incorporating copper and iron in nickel based layered double hydroxides. This work examines how replacing cobalt alters surface chemical interactions and electrochemical properties. These cobalt free electrodes are evaluated separately in supercapacitor and thermoelectrochemical configurations to demonstrate that the functional roles previously supported by cobalt can be achieved through alternative transition metal substitutions. This chapter provides an environmentally conscious direction for electrode development while maintaining the ability to operate across distinct electrochemical platforms. Overall, this thesis demonstrates a material-centred strategy in which nickel-based nanostructured electrodes are designed to function reliably in two separate electrochemical applications. By evaluating the same materials independently in supercapacitor and thermoelectrochemical systems, the work establishes how structural and compositional tuning enables consistent performance across both charge-storage and heat-to-electricity conversion environments. The findings offer pathways for designing electrodes that are adaptable, compositionally tunable and suitable for sustainable energy applications.
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Keywords
Nickel-based nanostructured electrodes , Asymmetric supercapacitors , Thermoelectrochemical cells , Bifunctional energy materials and structure-property-performance relationships
Citation
Palanisamy, R. R. 2025. Bifunctional nickel-based electrodes for electrochemical energy storage and low-grade heat harvesting. PhD Thesis, University College Cork.