This thesis investigates the optimization of thin film oxygen electrodes (≤ 1000 nm) deposited by Pulsed Injection-Metal Organic Chemical Vapor Deposition (PI-MOCVD) and their subsequent electrochemical characterization. The study focuses on nano-columnar porous thin films of La₂NiO_4+δ (L2NO4), a mixed ionic-electronic conducting (MIEC) material and promising oxygen electrode for intermediate- to low-temperature Solid Oxide Cells (SOC). A 3D Finite Element Method electrochemical model was developed at the scale of the nano-columnar morphology, to predict the optimal film thickness and microstructure. These numerical insights guided the optimization of L2NO4 thin film deposition.

To further enhance the electrode performance, the possibility of partially substituting La with Pr was explored to increase the intrinsic activity of the material. Lanthanum-praseodymium nickelate (LaPrNiO_4+δ) thin films were successfully deposited using PI-MOCVD for the first time. Kinetic studies, including Electrical Conductivity Relaxation (ECR) and Electrochemical Impedance Spectroscopy (EIS), were conducted, along with short-term stability tests. Additionally, a novel setup was developed for in situ EIS measurements during PI-MOCVD deposition, providing valuable insights into the optimal thickness (number of pulses deposited) and the electrochemical-morphology relationship during growth.

Finally, the potential of L2NO4 as a cathode material for oxygen ion batteries (OIB), a new class of solid-state batteries, was explored. Both half-cell and full-cell configurations were successfully fabricated and tested, demonstrating the feasibility of combining under- and over-stoichiometric MIEC materials as OIB electrodes.