Design of Earth‐abundant transition metal-based electrocatalysts for sustainable electrolysis.

The urgent need to transition toward a sustainable and carbon-neutral energy system is driven by the depletion of fossil resources, rising global energy demands, and the accelerating impacts of climate change. Among the available strategies, hydrogen stands out as a clean, high-energy-density carrier capable of enabling a future energy economy based on renewable resources. Water electrolysis and fuel cells are central to hydrogen production and electrochemical utilization, but their large-scale deployment is limited by the cost, activity, and durability of electrocatalysts, particularly for multi-electron oxygen and hydrogen conversion reactions. This thesis explores advanced catalyst study across both acidic and alkaline environments, from noble-metal systems for water electrolysis to earth-abundant and single-atom catalysts for oxygen reduction and hydrogen evolution. This thesis investigates advanced electrocatalytic systems potentially used in the acidic Proton Exchange Membrane (PEMWE) and alkaline Anion Exchange Membrane (AEMWE) systems. The extensive target of improving catalytic activity and operational stability while reducing scarce noble metal reliance. The combination of novel and controlled synthesis strategies, structural characterization, and electrochemical evaluation, the work explores different classes of materials from nanostructured mixed-metal oxides for PEM water electrolysis to nanoengineering earth-abundant bimetallic and layered hydroxidederived catalysts for AEM systems, as well as single-atomic Co–N4 centers for hydrogen evolution and oxygen reduction reactions.