Synthesis of PGM-Free Electrocatalysts for Water Splitting in Anion Exchange Membrane Water Electrolysers

The global energy landscape is undergoing a profound transformation that involves the entire energy cycle, from production to conversion, storage and final utilization. Progressively reduction of the dependence on fossil fuels, main contributors to pollution and climate change, in favour of renewable energy sources in currently pursued. In this context, hydrogen has emerged as one of the most promising solutions to address both environmental and energy challenges. At present, global hydrogen production still largely derives from fossil fuels; however, water electrolysis, powered by renewable energy, represents a sustainable alternative. In alkaline media, this technology offers several advantages not requiring noble-metal-based catalysts, fluorinated polymers, or expensive corrosion-resistant materials within the cell, thus enabling a reduction in overall production costs. The water electrolysis process is based on two half-reactions: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Currently, the most effective catalysts for these reactions are noble-metal-based materials such as Pt/C, IrO₂, and RuO₂; however, their large-scale application is limited by their high cost and low availability. This doctoral research project addresses this technological challenge, which in recent years has attracted increasing scientific attention. The focus of the work has been on transition-metal alloys, particularly binary systems based on Ni, Fe, and Co, chosen for their electrocatalytic properties, abundance, and sustainability. For each system, synthesis, characterization, and electrochemical evaluation were carried out. In the first stage, a study was conducted on the synthesis and characterization of FeNi₃/FeNiOx nanoparticles, obtained through a simple aqueous synthesis using hydrazine as a reducing agent. However, hydrazine is hazardous to both the environment and human health; for this reason, subsequent efforts were directed towards the development of catalysts using alternative chemical agents with similar reducing power, but which are less expensive and less harmful. A synthetic strategy was therefore designed, inspired by the principles of green chemistry, including the use of harmless solvents, the reduction of undesirable by-products and auxiliary substances, the adoption of mild and easily scalable reaction conditions, and the use of cost-effective and widely available raw materials. In this way, through a two-step aqueous synthesis employing aluminium powder as the reducing agent, nanoparticles of FeNi₃/FeNiOx, FeCo₃/FeCoOx, and Ni₁₋ₓCoₓ/NiCoOx were obtained. In parallel with the development of these electrocatalysts, I also collaborated on the synthesis and characterization of membranes for integration into alkaline cells: the first based on styrene–acrylic acid and the second consisting of a copolymer of diallyldimethylammonium chloride and vinyl acetate, both developed in parallel with the University of Naples Federico II.