An exploration of plasmon-enhanced photocatalysis in gold-based systems: energy and environmental applications

Chachvalvutikul, Auttaphon 2025. An exploration of plasmon-enhanced photocatalysis in gold-based systems: energy and environmental applications. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This thesis investigates plasmon-enhanced photocatalysis using gold-based nanostructured catalysts as a sustainable approach to energy and environmental challenges. Gold nanoparticles, through localised surface plasmon resonance (LSPR), enhance light absorption, charge separation, and reaction selectivity. The study underscores the potential of plasmonic effects to improve photocatalytic performance and scalable synthesis for practical applications. The first study investigates the stability and activity of gold-deposited g-C3N4 in a continuous gas-phase CO2 hydrogenation reaction. The research highlights how the presence of gold accelerates the decomposition of g-C3N4 under H2 flow to various hydrocarbon products, raising concerns about the long-term stability of the popular g-C3N4 in such applications. Advanced characterisation techniques reveal that gold affects charge separation, which is linked to the accelerated catalyst degradation. This chapter emphasises the importance of evaluating catalyst stability in plasmon-enhanced photocatalysis. The second study focuses on the selective photocatalytic reduction of nitrate to ammonia, crucial for nitrogen waste recycling. A reduced TiO2 catalyst decorated with gold-copper (AuCu) alloys was developed, achieving high ammonia yields (3.0 ± 0.1 mmol g-1 L-1) and a quantum yield of 36.4 ± 0.8% under dual-wavelength light (365 nm and 520 nm). The enhanced performance is attributed to improved light absorption, longer exciton lifetimes, and suppressed hydrogen evolution due to the LSPR of AuCu alloy and the synergy of gold and copper. Dual-wavelength irradiation provides the direct evidence of LSPR enhancement for this reaction for the first time. Mechanistic studies reveal that ammonia forms through nitrate deoxygenation and hydrogenation, driven by HCOO• radicals and gold-facilitated hydrogen transfer. The catalyst’s efficiency and stability highlight its potential for practical wastewater treatment applications. The final study explores photocatalytic hydrogen peroxide (H2O2) production using crystalline g-C3N4 derivatives, poly(heptazine imide) (PHI), poly(triazine imide) (PTI), and PHI/PTI composites. Incorporating gold nanoparticles into the PHI/PTI composite significantly enhances H2O2 yield. Despite stability challenges, the system demonstrates strong potential for practical H2O2 generation in continuous flow applications.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Chemistry
Date of First Compliant Deposit:	9 September 2025
Last Modified:	10 Sep 2025 08:40
URI:	https://orca.cardiff.ac.uk/id/eprint/181018

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