Novel Heterogeneous Photocatalysts for the Generation of H2O2 and CO2-Reductions

Promovendus/a: Peng Ren

Promotor(en): Shoubhik Das

This thesis explores the development and application of novel heterogeneous photocatalysts for environmentally sustainable production of hydrogen peroxide (H₂O₂) and CO₂ reduction. Utilizing sunlight as an energy source, these photocatalytic processes aim to address the global energy demand and reduce dependence on non-renewable energy sources while mitigating climate change impacts. Conventional methods of H₂O₂ production rely on hazardous chemicals, generating considerable waste. In contrast, photocatalytic H₂O₂ synthesis presents a cleaner alternative, with fewer harmful by-products. Similarly, the rising CO₂ levels, primarily due to fossil fuel combustion, contribute significantly to global warming. Photocatalytic CO₂ reduction, integrating Carbon Capture and Utilization (CCU) strategies, offers a promising solution by capturing CO₂ from exhaust gases and repurposing it for various applications, thus reducing emissions.

The thesis begins with an introduction to semiconductor photocatalysts, with a focus on BiOBr-based, single-atom, and g-C₃N₄-based catalysts, covering their synthesis, photocatalytic applications, and associated reaction mechanisms. Subsequent chapters delve into the specific catalysts developed for H₂O₂ production and CO₂ reduction.

In Chapter 2, a lignin-supported BiOBr photocatalyst (LBOB) is presented, designed for direct H₂O₂ production from seawater. Various characterization techniques (e.g., XRD, SEM, UV-Vis, ssNMR, XPS) were employed to analyze its structural and optical properties. Results indicated that lignin enhanced the photocatalytic performance by providing structural stability, lowering reduction potential, and facilitating electron transfer via functional groups acting as electron sinks.

Chapter 3 introduces a manganese-based single-atom photocatalyst optimized for H₂O₂ production via water oxidation. The catalyst's structural and electronic properties were characterized using UV-Vis, EPR, XANES, EXAFS, HRTEM, XPS, and ssNMR. The Mn centers played a pivotal role in generating hydroxy radicals (•OH), crucial intermediates for H₂O₂ synthesis.

Chapter 4 examines an iron-based photocatalyst for converting CO₂-rich gas streams into valuable products, demonstrating an impressive carbon monoxide (CO) production rate. This catalyst’s efficiency highlights its potential for practical CCU applications, leveraging sunlight for sustainable chemical transformations.

These studies underscore the potential of advanced photocatalysts in achieving efficient, sustainable solutions for H₂O₂ production and CO₂ reduction, aligning with global environmental goals.