Multiple important electrochemical processes including hydrogen generation from water reply on acid-stable electrocatalysts for oxygen evolution reaction (OER). The material choice of OER electrocatalysts in acid is often limited to only two major types of oxides (e.g., RuO₂ and IrO₂). Recently, ternary compounds have been reported to have excellent OER performance. Among them, our group developed pyrochlore-type electrocatalysts of various compositions. Yttrium ruthenate (Y₂Ru₂O_7-δ) was shown to have significantly enhanced performance towards OER in acid media over both RuO₂ and IrO₂ catalysts at current density about 1 mA/cm² [1]. It has an onset overpotential of 190 mV in 0.1-M perchloric acid solution. Tafel plots show the Y₂Ru₂O_7-δ catalyst had enhanced activity from 55 mV/dec for the first cycle to 46 mV/dec for the 10,000th cycle. In comparison, the OER performance for RuO₂ catalyst degraded from 61 mV/dec for the first cycle to 72 mV/dec for the 10,000th cycle under the same testing conditions. A range of techniques including X-ray absorption spectroscopy (XAS) and computational tools such as density functional theory (DFT) calculation have been used to understand the structural origins of enhanced performance. Our preliminary data suggest a low valence state in yttrium ruthenate (Y₂Ru₂O_7-δ) favors the high OER activity, while lowered band center energy for the overlap between Ru 4d and O 2p orbitals contributes to the stability. A systematic study on the structural origin for high OER performance has further been carried out using a series of A₂Ru₂O_7-δ pyrochlore-type electrocatalysts and will be presented in this talk. Strategies for improving the overall performance of these OER catalysts will also be discussed [2,3].

References:

1. M. Kim,^# P.-C. Shih,^# K.-C. Tsao, Y.-T. Pan, X. Yin, C.-J. Sun, H. Yang, J. Am. Chem. Soc., 2017, 139, 12076-12083 (#: equal contribution).
2. M. Kim, X. X. Chen, Y.-T. Pan, P.-C. Shih, H. Yang, J. Electrochem. Soc., 2017, 164, F1074-F1080.
3. M. Kim, X. X. Chen, P.-C. Shih, H. Yang, ACS Sustainable Chem. Eng., 2017, 5, 10190-10917.