Elevating IrOx acidic oxygen evolution activity using SnO2-rGO hybrid support

Abstract

• IrO x electrocatalysts on SnO 2 -rGO hybrid support for acidic OER were synthesized. • SnO 2 –rGO hybrid supports imparted active sites to the IrO x particles. • The OER activity of the catalysts was tuned by varying the Ir oxidation states. • IrO x on SnO 2 -rGO showed 10-fold higher mass activity than Ir black catalyst. Recently, Ir-based catalysts have been deposited onto high-surface-area and highly conductive materials to decrease noble metal loading in electrodes and thus increase the commercial viability of proton exchange membrane (PEM) water electrolyzers. carbon material supports impart active surface areas to the catalyst and metal-based supports enhance stability, thus improving the electrode performance for the energy-intensive and sluggish oxygen evolution reaction (OER). Herein, iridium oxide (IrO x ) electrocatalysts supported on a SnO 2 -reduced graphene oxide (rGO) composite (denoted as IrO x /SG) were used for the OER catalysis in acidic media. The effects of the SnO 2 –rGO hybrid support composition on the morphology, structure, surface composition, and performance of the IrO x catalyst were investigated. IrO x /SG catalysts were synthesized using ultrasonic spray pyrolysis and a modified polyol method. SnO 2 –rGO supports were employed to provide more anchoring sites for catalyst nanoparticle deposition and to modulate the catalytic activity and stability. Among the tested samples, the IrO x /S 80 G 20 catalyst (i.e., IrO x nanoparticles on 80 wt% SnO 2 and 20 wt% rGO support) showed the best OER performance. It exhibited a 10-fold higher mass activity than that of the commercial Ir black catalyst, which is possibly due to its high electrochemically active surface area (ECSA) and Ir 3+ ion and oxygen vacancy concentrations.