Hydrogen is recognised as a clean energy carrier that could play a key role in reducing global carbon emissions. In Proton Exchange Membrane Water Electrolysers (PEM WE), the hydrogen evolution reaction (HER) takes place at the cathode, where protons from the acidic electrolyte combine with electrons to form hydrogen gas. Catalysts are essential to this process, as they reduce the activation energy required for the reaction. Noble metals such as platinum are the benchmark materials for HER catalysts due to their exceptional activity and stability. However, their scarcity and high cost limit large-scale adoption. Non-noble catalysts, including transition metal-based materials such as nickel, molybdenum, and cobalt compounds, are attractive alternatives due to their lower cost and abundance. Despite these advantages, non-noble catalysts are more susceptible to degradation under the acidic conditions of PEM WE. The degradation of non-noble metal catalysts can arise from several processes, which often are interdependent. While the...
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