Síntese e caracterização da perovskita LaNiO₃ dopada com Ir e Ru e visando a exsolução para aplicação em reação de evolução de oxigênio

Abstract

The growing concern over the use of renewable and efficient energy sources to replace fossil fuels and mitigate environmental problems in pursuit of a sustainable future is a widely discussed topic. Green hydrogen has emerged as a viable alternative to fossil fuels, as it is a clean, renewable, and energy-efficient resource with potential applications in the energy sector and across various industries. It can be produced through water electrolysis — a process that uses renewable energy to split water molecules and generate hydrogen — making it an environmentally friendly method. The search for new functional materials that combine high stability and efficiency with reasonable cost is essential for advancing renewable energy technologies. Among these, perovskite-type oxides stand out as an important class of materials due to their favorable electronic properties and potential for application in renewable energy systems, particularly in the oxygen evolution reaction (OER), which is a critical step in water electrolysis for green hydrogen production. The perovskite LaNiO₃ is considered a promising candidate for OER applications; however, it presents some instability at the Ni³⁺ active site — a limitation that can be mitigated through targeted doping. Doping and the exsolution of nanoparticles have proven to be effective strategies for stabilizing perovskite structures and enhancing their electrocatalytic activity. This study aims to investigate the electrocatalytic properties of the LaNi₁₋ₓIrₓO₃ and LaNi₁₋ₓRuₓO₃ perovskite series, examining the effects of incorporating Ir⁴⁺ and Ru⁴⁺, as well as the conditions required to promote their exsolution and their impact on OER performance. The perovskite powders were synthesized using the simultaneous precipitation method, followed by a calcination step in an O₂ atmosphere, and then subjected to a thermal treatment in a reducing 5% H₂/N₂ atmosphere to induce the exsolution of Ir and Ru nanoparticles. The samples were characterized in terms of their structural, morphological, and electrochemical properties.