High-Performance Praseodymium Doped Pyrochlore-Type Yttrium Ruthenate Electrocatalysts for Proton Exchange Membrane Water Electrolysis

Abstract

Proton exchange membrane water electrolysis (PEMWE) is an advanced and effective solution to the primary energy storage which allows for direct production of hydrogen from water. Due to the harsh electrochemical environment (e.g., high anodic overpotential, the presence of strong oxidants, low PH) and the sluggish electrode processes, precious metal compounds have been chosen as electrocatalysts in PEMWE [1]. The development of low-cost, highly active and stable oxygen evolution reaction (OER) catalysts remains an important challenge. Pyrochlore yttrium ruthenate (Y2Ru2O7−δ) has significantly enhanced performance over conventional IrO2 electrocatalyst towards OER and high stability in acid media [2]. However, Y2Ru2O7−δ is limited by its low electrical conductivity related to the n-type semiconducting behavior [3]. Doping the A site of the pyrochlore structure (A2B2O7−δ) is a strategy to improve the electrical conductivity of pyrochlore materials. In this work, novel yttrium–ruthenates compositions doped with Pr were synthesized by sol-gel method. Electrochemical measurements in acidic media showed that Pr doped yttrium pyrochlore catalysts possess high OER activity and stability. The OER overpotentials of Y2Ru2O7−δ and Y1.8Pr0.2Ru2O7−δ are 310 mV and 300 mV at 10 mA/cm2, which is lower than that of IrO2 (340 mV). The Tafel slopes for Y2Ru2O7−δ and Y1.8Pr0.2Ru2O7−δ are 40 mV/dec and 36 mV/dec, respectively, in comparison with 42 mV/dec for IrO2. The superior activity of Y2Ru2O7−δ and Y1.8Pr0.2Ru2O7−δ measured by current density remained largely unchanged even after 2000 cyclic voltammograms (CVs) cycles, only decreasing by 17% and 5.6%, respectively. In contrast, IrO­2 catalyst lost 46% of its activity. Figure 1. OER performance of pyrochlore Y2Ru2O7, Y1.8Pr0.2Ru2O7 and reference IrO2 electrocatalysts. (a) CVs cycles from 1st to 2 000th. Inset shows the comparison of current densities for yttrium ruthenate and IrO2 at 1.52 V versus RHE. (b) Tafel plots. [1] Q. Feng, X.Z. Yuan, G. Liu, B. Wei, Z. Zhang, H. Li, H. Wang, Journal of Power Sources, 366 (2017) 33-55. [2] J. Kim, P.C. Shih, K.C. Tsao, Y.T. Pan, X. Yin, C.J. Sun, H. Yang, J Am Chem Soc, 139 (2017) 12076-12083. [3] C. Abate, V. Esposito, K. Duncan, J.C. Nino, D.M. Gattia, E.D. Wachsman, E. Traversa, Journal of the American Ceramic Society, (2010). Figure 1