Abstract
Development of high performance electrocatalysts for oxygen evolution reaction (OER) in acidic media remains a challenge for direct water splitting using an electrolyzer. Recently, Ruddlesden-Popper phase Sr2IrO4 was discovered to be an efficient OER catalyst because of its unique structure, which consists of layers of both rock salt and perovskite phases simultaneously. In this study, we prepared a series of B-site mixed, Ruddlesden-Popper phase of Sr2(RuxIr1−x)O4 and examined their electrocatalytic properties for OER in acidic media. Through partial substitution of Ru in the B-site of Ruddlesden-Popper phase materials, we achieved much enhanced OER performance for this series of Sr2(RuxIr1−x)O4 electrocatalysts, among which Sr2(Ru0.5Ir0.5)O4 exhibited the best catalytic activity with a current density of 8.06 mA/cm2 at 1.55 V and a Tafel slope of 47 mV/dec. This current density is three times higher than that of Sr2IrO4. The B-site mixed Sr2(Ru0.5Ir0.5)O4 retained good stability in acidic conditions for > 24 h at 10 mA/cm2. A range of techniques were used to characterize the crystal and electronic structures of the Sr2(RuxIr1−x)O4 samples. Our data indicate that the improved OER performance can be correlated to the formation of high level of hydroxyl groups and the enhanced overlap between Ir/Ru 4d and O 2p orbitals, revealing a new way for the design of efficient OER electrocatalysts by regulating their composition and electronic structures.
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