An active group focusing on certain aspects of the chemistry and hydrometallurgy of the platinum group metals (PGMs) is being established at the North-West University (NWU), which is located in South Africa’s North-West Province, also known locally as the Platinum Province as the majority of the world’s platinum reserves are located and mined here.
Our research focus can be summarised as focussing on “electron transfer to and from platinum group metals as well as the facilitation of electron transfer by platinum group metals”, and can be schematically depicted as follows:
Key Focus Areas:
The key research focus areas include photocatalysis, leaching and electrocatalysis, as these are the areas where electron transfer processes find application in fields such as recovery, processing, and fuel cells & electrolyzers.
Electrolyser for the production of hydrogen
We are embarking on a project to develop, characterize and test different PGM electrocatalysts for ultimate application in electrolysers for hydrogen production. As fossil fuels are not renewable, together with their negative impact on the environment in contributing to the greenhouse effect and global warming, there is a push for developing a future hydrogen economy. Electrolysers produce hydrogen through an electrochemical process and fuel cells produce electricity through an electrochemical process employing, amongst other things, hydrogen. Both of these devices employ an electrocatalyst at the cathode and anode, which in the majority of cases employ a single PGM, a combination of PGMs, or a combination of PGMs and base metals.
Recovery of PGMs in the ppm range holds great benefit if it could be accomplished economically and on an environmentally friendly manner. Our research focuses on the development of recovery processes through the application of different photocatalysts, e.g. TiO2 and others, under UV-illumination, for the recovery of especially Pt, Pd and Rh from solution. Not only do we investigate the photocatalytic reduction of the PGMs, but we also investigate different reactor setups so as to obtain the most optimal configuration.
Photocatalytic Charge Generation Pathways
Traditionally the PGMs are being leached employing rather aggressive methods, e.g. aqua regia, chlorine gas in a strong hydrochloric acid medium, etc. This results in increased costs due to continuous maintenance of equipment and high reagent consumption due their volatility. Research is underway to investigate the effectiveness of less aggressive lixiviants.
Support Focus Areas:
The photocatalytic reduction of PGMs depends very much on the actual PGM-complexes in solution, as shown by our research, whereas the leaching of PGMs depend very much on the stability of specific PGM-complexes in solution. As the formation constants (stability constants) of PGMs are to a large extent nonexistent, we conduct speciation studies employing spectrophotometry and potentiometry to provide us with these data.
Making use of rotating disk working electrodes (RDE) manufactured with the specific PGM under investigation, an electrochemical investigation provides information on the potentially optimum conditions for the leaching of the specific PGM. Rotating ring disk electrode (RRDE) studies of the PGM electrocatalyst under investigation, provides information on the effectiveness of the electrocatalyst in catalysing specific electrochemical reactions.