Bouscarrat, Luc and Gupta, Gaurav and Dawson, Richard and Bimbo, Nuno (2023) MXenes as Support for Electrocatalysts towards Oxygen Reduction Reaction in Alkaline Media. PhD thesis, Lancaster University.
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Abstract
Due to increasing concerns about the ever increasing energy demand, the global energy system needs to transition away from fossil fuels, as they have been one of the main causes for climate change and air pollution. Fuel cells offer a good alternative to conventional thermal devices, as they usually use hydrogen and oxygen to produce electricity without greenhouse gases emissions. One of the main drawbacks to fuel cell commercialisation is the use of expensive catalysts, such as platinum, and their long-term stability under operation. Therefore, the design and study of cheap and durable catalysts is required to push the development of fuel cells. MXenes, a new family of two-dimensional transition metal carbides and nitrides materials, have shown some potential as support for ORR catalysts. However, the performance of electrocatalysts is directly related to the available surface where the electrochemical reaction could take place, and MXenes have pretty low specific surface areas compared to conventional supports used in the field of catalysis. This thesis reports the development of a synthesis method focused on improving the final catalyst surface area using MXene (Ti3C2) as support, by intercalating the precursors between the MXene layers before annealing. This is shown to lead to the formation of porous MXene structures, with increased surface area and decomposition products from the precursors on the surface of the MXene layers, which hindered the MXene layer restacking during thermal treatment. The samples where then tested in a three-electrode setup using the RDE method to evaluate the ORR performance of the synthesized materials. It was found that the addition of the precursors improved the overall performance of the materials. The different samples were also characterized to understand the connection between physico-chemical properties and electrochemical properties.