Radiofrequency Plasma‐Assisted Pulsed Laser Deposited Pt/TiO_xN_y Coatings on Multi‐Walled Carbon Nanotubes as Gas Diffusion Electrodes for the Oxygen Reduction Reaction

Abstract This study reports on the fabrication and characterization of novel multilayered electrocatalyst nanostructures for the oxygen reduction reaction (ORR). Thin titanium oxynitride (TiO_xN_y) coatings are deposited on a forest of multi‐walled carbon nanotubes (MWCNTs), directly grown on a stainless‐steel mesh, by capacitively coupled radiofrequency plasma‐assisted pulsed laser deposition (RF‐PAPLD) in a N₂ environment. The resulting high‐surface‐area binder‐free electrode is further coated with a low quantity of well‐dispersed Pt nanoparticles (NPs) by PLD in an inert atmosphere. High‐speed imaging of the laser‐induced plasma expansion provided evidence of a higher kinetics of the expanding plume at higher RF plasma powers, changing the morphology of the TiO_xN_y coatings. X‐ray photoelectron spectroscopy demonstrated that the coatings are homogeneous throughout their thickness, where the TiN, TiON, and TiO bonds exist in all samples. The oxygen content of the coating increases with the RF plasma power. Both TiO_xN_y/MWCNT and Pt/TiO_xN_y/MWCNT nanostructures are tested in a gas diffusion electrode setup to evaluate their activity in the ORR. The results showed the superior activity of the Pt/TiO_xN_y‐0.03 Torr‐30 W/MWCNT, reaching the highest current density of 180 mA cm⁻², while the commercial Pt/C electrode with the same Pt loading yielded 105 mA cm⁻² at the potential of 0.5 V.