Supported metal nanoparticles as photocatalysts for the generation of H2 from waste

Maashi, Saleha 2026. Supported metal nanoparticles as photocatalysts for the generation of H2 from waste. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The objective of this work is to develop and understand efficient, stable, and cost effective TiO2-supported catalysts for sustainable H2 production by understanding and probing the effect of catalyst composition, synthesis and reaction conditions on the performance. For this purpose, two photocatalytic routes for H2 production were examined: the photoreforming of aqueous glycerol and photocatalytic decomposition of aqueous urea. Under the tested conditions, glycerol photoreforming delivered higher H2 evolution rates, while urea photodecomposition resulted in comparatively lower H2 generation. Within the glycerol photoreforming system, TiO2-supported monometallic and bimetallic catalysts containing Pt, Cu, and Fe were studied at a very low loading of 0.5 wt%. Among these, the 0.5 wt% Pt/TiO2 catalyst showed the highest H2 productivity. H2 evolution was found to be dependent on the metal loading, catalyst mass and the catalyst preparation method. The catalyst synthesis methodology played a key role in determining performance. Wet impregnation (WI), sol immobilisation (S-Im), and wet impregnation followed by sodium borohydride reduction (WI-NaBH4) were each found to produce distinct differences in nanoparticle dispersion, metal oxidation states, and charge carrier dynamics. To enhance the economic feasibility of the system, 0.5 wt% Cu/TiO2 catalysts prepared using the WI, S-Im, and WI-NaBH4 methods were investigated as cost-effective alternatives to noble metal-based TiO2 catalysts. Cu modification of TiO2 altered the optical response of the catalyst and helped promote charge separation through a Schottky barrier, but issues like metal leaching and particle aggregation ultimately limited its long-term photocatalytic performance. The photocatalytic activity of the 0.5 wt% Cu/TiO2 catalyst prepared with the WI-NaBH4 method was higher than that of other methods due to the lower charge-transfer resistance, the Schottky barrier effect, and the better charge separation. This work has further examined bimetallic catalysts using transition metals. The two bimetallic catalysts studied in this work are 0.5 wt% FePt/TiO2 and 0.5 wt% CuPt/TiO2 prepared by WI, S-Im, and WI-NaBH4. Both catalysts presented higher photocatalytic activity than their respective monometallic catalysts (0.5 wt% Cu and Fe supported on TiO2). The 0.5 wt% FePt/TiO2 (WI) catalyst demonstrated a high-performing combination of high H2 production and a substantially reduced reliance on precious metals. The improved catalytic activity was attributed to the electronic interactions that occur when both metal components interact with each other, resulting in changes to their interfacial electronic structures. Alongside this, the work assessed the photocatalytic decomposition of aqueous urea as an alternative pathway for H2 generation. The results from the urea system indicated that H2 generation depends strongly on urea concentration, catalyst mass, and solution alkalinity, revealing that urea can act as an effective hole scavenger for H2 evolution. Although the 0.5 wt% Pt/TiO2 catalyst showed the highest H2 production among the catalysts tested, outperforming both 0.5 wt% NiPt/TiO2 and 0.5 wt% Ni/TiO2 in the aqueous urea system, the overall H2 production was lower than that achieved during glycerol photoreforming. This highlights the need for further optimisation of the urea-based process to enhance H2 production. The strong performance of the 0.5 wt% Pt/TiO2 catalyst may be due to its work function (Φ) and ionisation potential (IP), which promote efficient electron transfer, suppress charge recombination, and enable more effective trapping and utilisation of photogenerated electrons, resulting in improved H2 evolution. Characterisation results indicate that this enhanced activity is directly linked to improved charge separation and stronger electronic interactions at the metal-TiO2 interface, as demonstrated by TEM, XPS, UV-Vis DRS, PL, TCSPC, PESA, and EIS analyses.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Chemistry
Date of First Compliant Deposit:	2 September 2026
Last Modified:	02 Sep 2026 09:41
URI:	https://orca.cardiff.ac.uk/id/eprint/189331

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