23/02/2026
Recovery of platinum group metals into electrocatalytic nanoparticles by gas-diffusion electrocrystallization (GDEx)
The sustainable recovery of platinum group metals (PGMs) is crucial to meet rising global demands of these metals, particularly within the European Union. PGMs (i.e., platinum, Pt; palladium, Pd; rhodium, Rh; iridium, Ir; ruthenium, Ru; and osmium, Os) are vital for technologies like fuel cells and automotive catalytic converters. This PhD thesis focuses on developing and optimising the gas-diffusion Electrocrystallization (GDEx) process to recover PGMs from secondary sources such as spent automotive catalysts (SACs). GDEx is a novel electrochemical method that allows for the recovery of metals as nanoparticles (NPs), enabling their direct application as electrocatalysts.
This research aimed: (1) to understand the fundamental mechanisms of the GDEx process, especially the roles of electrochemically generated CO and H₂ in precipitating Pt, Pd and Rh, and (2) to optimise the GDEx process for producing PGM NPs with high surface areas, tailored for electrocatalytic applications, particularly the methanol oxidation reaction (MOR) of direct methanol fuel cells (DMFCs). Additionally, the research aimed to evaluate the long-term stability and performance of the GDEx-produced nanoparticles compared to state-of-the-art commercial catalysts.
Key findings from this research include a detailed mechanistic understanding of how CO and H₂, formed during the electrochemical reduction of CO₂, drive the selective recovery of PGMs in their metallic form. The optimised GDEx conditions successfully synthesised Pt and Pt-Pd alloy NPs with exceptionally high surface areas. These nanoparticles, stabilised using polyvinylpyrrolidone (PVP), not only demonstrated superior electrocatalytic activity for methanol oxidation in both acidic (Pt and Pt-Pd alloy NPs) and alkaline media (Pt NPs) but also significantly outperformed commercial Pt/C catalysts in terms of activity and stability, highlighting the potential of the GDEx process.
Furthermore, the thesis explored the direct application of GDEx in recycling PGMs from complex leachate solutions, such as those derived from SACs. High recovery efficiencies were achieved, and the recovered PGM NPs were successfully tested as electrocatalysts for methanol oxidation, highlighting the potential of GDEx as a scalable and sustainable method for PGM recovery and reuse. This novel approach offers environmental and economic benefits, reducing energy consumption and resource dependency while addressing the urgent need for efficient recycling technologies.
