Innovative nanostructured BANB _0.2 IR _0.8 O ₃ catalyst for oxygen evolution reaction in severe sulphuric acid environment

Abstract In this study, the deactivation of BaNb 0.2 Ir 0.8 O 3 nano catalyst in sulphuric acid environment was addressed. The BaNb 0.2 Ir 0.8 O 3 nano catalyst was synthesized using activated reactive synthesis (ARS) method. The synthesized material is intended to be used in the zinc electrowinning process to decrease the overpotential for the oxygen evolution reaction (OER), thus improving the energy efficiency of the process. ARS combines solid state reaction (SSR) with mechanosysnthesis techniques, that is, ball milling. The XRD analysis proved the formation of the crystalline structure after solid‐state reaction. High‐energy ball milling (HEBM) resulted in a decrease in crystallite size of the solid, composed of highly agglomerated nano particles. The particles were then deagglomerated using low‐energy milling, resulting in a 20‐fold increase in the specific surface area (SSA) of the powders compared to the initial SSR step. These catalysts could be deactivated by the formation of the BaSO 4 phase in a sulphuric acid environment. This challenge was tackled via partial leaching of Ba from the catalyst surface before the electrolysis process. XPS analysis was used to characterize the chemical composition of the catalyst. Electrochemical measurements showed that the new synthesis route, resulted in a twofold reduction in Tafel slope and improved catalytic activity and stability in sulphuric acid environment. The samples exhibited 230 and 280 mV overpotentials at two different current densities of 100 and 500 A/m 2 , respectively as well as a very good stability compared to the samples without Ba leaching.