Development and Evaluation of PGM-Free Anodic Electrodes for the Oxygen Evolution Reaction in AEM Electrolyzers

The transition to renewable energy must address its intermittency. Green hydrogen, produced CO2-free through renewable-powered water electrolysis, offers a solution as an energy carrier. This thesis investigated the emerging technology of Anion Exchange Membrane Water Electrolyzer (AEMWE), with a focus on PGM-free anodic electrocatalysts for the Oxygen Evolution Reaction (OER) based on different catalytic compositions: NiFe2O4, NiO, Co3O4. The research included the formulation and optimization of anodic catalytic inks, the deposition of the catalytic layer onto nickel felts using the Catalyst Coated Substrate (CCS) methodology, the execution of preliminary thermal treatments on all the electrodes at 120°C, as well as additional treatments at 350°C on NiFe2O4 to evaluate their effects on catalytic properties. Morphological and structural properties were investigated through SEM/EDS and XRD analyses to establish correlations with performance and stability, which were evaluated through electrochemical tests. The thermally treated NiFe2O4 samples were analysed in terms of morphology, structure, performance and durability and the results were compared with those of untreated samples. It appeared that although the higher-temperature treatment effectively reduced the average particle size and eliminated impurities, it also led to a decline in mechanical integrity, being unsuitable for applications requiring long-term durability, such as electrolyzers. In contrast, the lower-temperature treatment preserved the structural integrity while moderately decreasing the average particle size, offering a compromise between catalytic activity and durability. Finally, from a comparative evaluation, among the analysed catalysts, NiFe2O4 emerges as the most suitable candidate for long-term industrial applications, combining good catalytic activity and excellent stability. While NiO and Co3O4 demonstrated superior initial performance, their stability is limited compared to NiFe2O4.