Date of Award

2023-05-01

Degree Name

Doctor of Philosophy

Department

Chemistry

Advisor(s)

Sreeprasad Sreenivasan

Abstract

Catalysis is integral to our daily lives, as it streamlines and accelerates numerous chemical reactions essential for producing various materials, fuels, and chemicals. With the rising demand for clean, sustainable energy sources, optimizing catalytic materials and processes becomes increasingly vital. In the realm of renewable energy production, catalysis is crucial for efficiently converting energy from sustainable resources, such as solar, wind, and biomass, into chemical energy stored in fuels or directly into electrical energy.The electronic charge distribution in materials significantly influences their physical and chemical properties, facilitating the development of advanced electronic, optoelectronic, sensing, and energy conversion devices. Since catalysis inherently involves electron transfer, electronic modulation can substantially enhance the performance of catalysts. Thus, to meet future energy demands, it is imperative to harness the power of catalysis in renewable energy devices, propelling us towards a sustainable future while mitigating climate change impacts and reducing dependence on polluting fossil fuels. Critical to addressing future energy needs are electrochemical energy generation systems, such as fuel cells, metal-air batteries, and comprehensive water-splitting devices. At the core of these technologies are the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), which are fundamental to their effectiveness. The efficiency of all these reactions depends on catalysts, and developing efficient, inexpensive, and durable catalysts is essential for their widespread adoption and the sustainability of the future energy sector. In recent decades, the development of electrocatalysts for electrocatalytic water splitting applications has evolved from trial-and-error methodologies to rational and directed approaches at the atomic level, primarily through modulating the electronic properties of active sites. This thesis investigates the effect of charge modulationâ??specifically, employing techniques such as chemical doping, strain, and heterostructure formationâ??and its implications for electrochemical energy generation. The primary focus is on noble metal-free nanostructured materials and low-dimensional material-based electrocatalysts, which exhibit more significant impacts on their physical, chemical, and electronic properties compared to their bulk counterparts when utilizing these strategies. Apart from electrochemical energy applications, electronic charge modulation also plays an important role in determining the efficiency of materials for analytical sensing. The thesis also focuses on the potential of charge modulation to enhance the sensing performance of materials for pollutants, such as heavy metal ions, using two different analytical sensing techniques, Photoluminescence (PL) based, and Surface Enhanced Raman Spectroscopy (SERS). Specifically, in photoluminescence-based sensing using quantum dots the band structure modulation via foreign atom doping can be utilized to improve quantum efficiency and limit detection. The thesis also explores innovative strategies for spin modulation in materials. In chemistry, many chemical processes, in addition to their dependence on free and activation energies, are electron spin dependent. Recognizing the potential role of hydrogen in future energy systems, we select the OER as the model spin-dependent chemical process and investigate how spin modulation can influence its overall efficacy. Specifically, we investigate the role of spin modulation in nanostructured materials using external aids, such as magnetic fields and chiral molecule incorporation. Our findings reveal that external magnetic fields and chiral spin potentials can induce spin polarization in materials, lifting the degeneracy of spin-up and spin-down electrons. Our studies indicate that such spin polarization can lead to enhanced OER activity by facilitating a lower tunneling barrier pathway and thereby aiding in selective electron transfer with the desired spin. In summary, this thesis underscores the profound importance of employing innovative techniques to accurately manipulate materials' charge and spin properties, which hold great promise for a wide range of applications. By carefully selecting materials and employing external aids in a rational manner, it is possible to achieve exceptional sensing and electrocatalytic performance. The discoveries presented here not only contribute to a deeper understanding of charge and spin-dependent effects in nanostructured materials but also offer valuable insights for designing materials with advanced functionalities tailored to specific applications. The findings have the potential to inform and inspire the development of next-generation materials that harness charge and spin modulation, ultimately enabling breakthroughs in fields such as energy conversion, sensing, and optoelectronics, paving the way towards a more sustainable and technologically advanced future.

Language

en

Provenance

Recieved from ProQuest

File Size

p.

File Format

application/pdf

Rights Holder

Aruna Narayanan Nair

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Included in

Chemistry Commons

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