In alkaline water electrolysis (AWE), the oxygen evolution reaction (OER) is a key limiting electrochemical reaction because of its complex reaction pathway through a four-electron transfer process, and high overpotential. This results in sluggish kinetics and increased energy consumption, due to hindering efficiency and scalability of hydrogen production, thus posing stringent catalyst requirements. One approach to overcome this is through rational catalyst design of such as perovskite oxides and the exsolved nanoparticle systems. Perovskite oxides (ABO₃) have emerged as highly versatile materials in this context, offering tuneable structures, compositional flexibility, and mixed ionic–electronic conductivity. These properties allow for the optimisation of catalytic performance, particularly for the OER and hydrogen evolution reaction, positioning perovskites as promising, scalable catalysts for efficient AWE systems. Exsolution refers to the thermally driven formation of catalytically active metal nanoparticles, which emerge from the perovskite lattice and become anchored to the surface under reducing conditions, thereby enhancing catalytic performance through increased surface reactivity and stability.

This study examines the perovskite oxide Sr₀.₉₅Ti₀.₃Fe₀.₆Cu₀.₁O₃ (STFCu), a composition deliberately engineered to incorporate earth-abundant, non-precious elements while aiming to achieve a synergistic balance between structural robustness and enhanced electrocatalytic performance. The low cost, abundance, and compatibility of copper make it suitable as both a lattice dopant and electrode component.

The present work focuses on optimising the sol-gel synthesis of STFCu perovskite by controlling calcination time and temperature to achieve a pure phase perovskite. Phase purity and crystal structure are assessed using X-ray diffraction (XRD), with the overarching goal of comprehensively evaluating their structural, catalytic, engineering, and economic viability. A central objective involves the investigation of nanoparticle exsolution behaviour, examined using scanning electron microscopy (SEM). To assess the functional implications of this phenomenon, electrochemical characterisation (including cyclic voltammetry, linear sweep voltammetry, and Tafel slope) were conducted, revealing that surface–exsolved nanoparticles play a pivotal role in promoting reaction kinetics and electron transfer during the OER. The findings contribute to a more nuanced understanding of structure–activity relationships in copper–doped perovskites, and offer a foundation for the rational design of advanced OER electrocatalysts that combine high activity, long-term durability, and economic feasibility.