Structurally robust LaNiO3 perovskite catalyst for oxygen evolution reaction with limited surface self-reconstruction

LaNiO₃ perovskite is a promising oxygen evolution reaction (OER) electrocatalyst. However, establishing its structure-property relationships remains challenging because the instability of Ni³⁺ during synthesis promotes the formation of catalytically active Ni²⁺-containing secondary phases that obscure the OER behavior of LaNiO₃. Here, a facile and scalable citrate-assisted synthesis enables the reproducible preparation of single-phase LaNiO₃ nanoparticles at the gram scale. X-ray absorption spectroscopy (XAS), neutron diffraction, and thermogravimetric analysis confirm fully oxidized Ni³⁺-based perovskite with complete oxygen stoichiometry, negligible impurity content, and high reproducibility across batches. Electrochemical measurements reveal high OER activity, reflected by low Tafel slope of 45 mV dec^–1, while soft XAS, operando hard XAS, operando X-ray diffraction, and ab initio Pourbaix calculations show that LaNiO₃ remains structurally and electronically robust during OER operation, with minor transformations upon electrolyte exposure. These findings indicate that the oxidation state and structure of the precursor catalyst govern the activation pathway. Moreover, high OER activity can be achieved through limited surface adaptation to the electrolyte rather than extensive self-reconstruction. Beyond LaNiO₃, this work highlights the importance of controlling phase purity, crystal structure, and oxidation state of the precursor catalyst through scalable synthesis, enabling structure-property relationships and guiding the design of durable OER electrocatalysts.