Cost-effective electrodes based on mixed iridium-zirconium oxides for vanadium electrolyte rebalancing cell

Developing the mixed metal oxide (MMO) electrodes with high electrocatalytic activity, low cost of materials and long service life is an important and relevant task for various applications including the vanadium electrolyte rebalancing. In this work, the cost-effective electrodes based on mixed iridium-zirconium oxides were fabricated using the Pechini method followed by thermal decomposition. The Raman and XPS analysis of mixed IrO2–ZrO2 electrodes showed a partially crystalline (IrO2 and ZrO2) and partially amorphous (IrOx and ZrOx) structure. Conducted electrochemical tests demonstrated the high electrocatalytic performance of the electrodes with 15–30 mol% of Zr addition comparable to Ir-based electrodes toward the OER. Successful proceeding of the electrochemical reduction in the rebalancing cell was proved using operando absorbance spectra analysis of the reducing vanadium electrolyte. The results of a prolonged vanadium electrolyte electroreduction showed more effective performance of the cell with 70Ir–30Zr electrode than the same cell with 70Ir electrode under a high current density of 250 mA cm−2. This approach allows reducing the electrode cost with reducing the Ir loading without sacrificing the electrocatalytic properties with Zr adding.