Electrocatalytic stability of Ti based-supported Pt3Ir nanoparticles for unitized regenerative fuel cells

• Pt3Ir nanoparticles supported on TiC, TiCN and TiN materials have been investigated as bifunctional electrocatalysts.
• Pt3Ir/TiCN catalyst shows the highest activity toward oxygen reduction and evolution reactions.
• TiN-based catalyst suffers high passivation degree by dissolved oxygen.
• TiCN-based materials provide the best compromise between catalytic activity and stability.

PtIr (3:1) nanoparticles supported on TiC, TiCN and TiN were investigated as bifunctional electrocatalysts for the oxygen electrode of unitized regenerative fuel cells. The electrocatalysts were prepared by the ethylene glycol method. Physicochemical characterization was carried out by X-ray Diffraction, Transmission Electronic Microscope and X-ray Photoelectron Spectroscopy, meanwhile rotating ring-disk electrode and in situ Fourier transform infrared spectroscopy were employed to determine the electrochemical activity and stability. Results reveal the highest activity toward oxygen reduction and evolution reactions on TiCN-based materials, in addition to the best compromise between catalytic activity and stability. In this context, nitrogen loading appears to be an important factor for the catalyst performance and noble metal anchoring. It is observed an increment of particle agglomeration with nitrogen content in the catalyst support. Also, TiN-based catalyst presents the lowest noble metal inclusion and high passivation degree by dissolved oxygen; whereas TiC and TiCN based catalysts develop an anodic peak at ca. 1.1 V, which is associated to TiO2 and CO2 formation.