Activity and stability optimization of RuxIr1-xO2 nanocatalyst for the oxygen evolution reaction by tuning the synthetic process.

IrO 2 and RuO 2 are known as two of the best catalysts for the oxygen evolution reaction (OER) in acidic electrolyte. It is reported that RuO 2 has higher OER catalytic activity, while IrO 2 possesses better electrochemical stability during the OER process in acid. Therefore, many combined strategies have been proposed to utilize the advantages of both IrO 2 and RuO 2 catalysts in water electrolysis applications. In this article we describe how, by tuning the wet-chemical synthesis process in which the Ir precursor is added after the synthesis of RuO 2 nanoparticles (NPs) (two-step), the Ru 0.5 Ir 0.5 O 2 NPs have been synthesized to improve the OER catalytic activity in both acidic and alkaline media. In detail, the specific OER activity of the Ru 0.5 Ir 0.5 O 2 NPs (with a particle size of ca. 10 nm) is 48.9 μA cm−2 at an overpotential ŋ = 0.22 V (vs. RHE) and 21.7 μA cm−2 at ŋ = 0.27 V (vs. RHE) in 0.1 M HClO 4 and 0.1 M KOH, respectively. These values are higher than those for the one-step (Ir 0.5 +Ru 0.5)O 2 NPs (obtained by contemporaneously adding both Ru and Ir precursors), which are 19.5 and 15.5 μA cm−2 at the same measuring conditions, respectively. Additionally, with more IrO 2 component distributed on the particle surface, the two-step Ru 0.5 Ir 0.5 O 2 NPs show better OER catalytic stability than RuO 2 NPs. Image 1 • Two-step synthesis yields higher number of surface-Ir atoms on mixed Ru 0.5 Ir 0.5 O 2 NPs. • The particle size of Ru 0.5 Ir 0.5 O 2 NPs is relatively small, about 10 nm. • The high OER catalytic activities of two-step Ru 0.5 Ir 0.5 O 2 NPs are achieved. • Two-step Ru 0.5 Ir 0.5 O 2 NPs possess better OER stability than one-step synthesized NPs. [ABSTRACT FROM AUTHOR]