Effect of TiCN Sublayer in Improving the Efficiency and Durability of Bifunctional Oxygen Electrode in URFC

A unitized reversible fuel cell (URFC) is a promising technology that combines the functions of hydrogen production and electricity generation in a single device. However, the insufficient corrosion resistance of the bifunctional oxygen electrode significantly limits the large‐scale implementation of this technology. This work investigates the influence of different architectures of the catalytic layer (CL) (layered and mixed loading of electrocatalysts, as well as the application of a titanium carbonitride (TiCN) sublayer) on the efficiency and durability of the oxygen electrode in fuel cell (FC) and water electrolyzer (WE) modes. A protocol for assessing electrode durability is proposed, involving cyclic recording of i–V curves in FC/WE modes, followed by testing the electrode in a potentiostatic mode at 1.65 V and 80°C for 30 min. The use of an electrode with a TiCN sublayer deposited by magnetron sputtering between platinum and iridium electrocatalysts doubled the device's service life compared to using a mixed loading of electrocatalysts. This effect is attributed to the reduced rate of Ir conversion to its oxidized form (IrO x ) due to the competitive oxidation of titanium in the sublayer, which also inhibits further corrosion processes.