Bote Zhao1 Lei Zhang1 Dongxing Zhen1 Seonyoung Yoo1 Yong Ding1 Dongchang Chen1 Yu Chen1 Qiaobao Zhang1 Brian Doyle1 Xunhui Xiong1 2 Meilin Liu1

1, Georgia Institute of Technology, Atlanta, Georgia, United States
2, South China University of Technology, Guangzhou, , China

Water splitting and rechargeable metal–air batteries are highly competitive options for a sustainable energy future, but their commercialization is hindered by the absence of cost-effective, highly efficient and stable catalysts for the oxygen evolution reaction (OER). Here we report the rational design and synthesis of a double perovskite PrBa0.5Sr0.5Co1.5Fe0.5O5+δ nanofiber as a highly efficient and robust catalyst for OER [1]. Co-doping of strontium and iron into PrBaCo2O5+δ (PBC) is found to be very effective in enhancing intrinsic activity (normalized by the geometrical surface area, ~4.7 times), as validated by electrochemical measurements and first-principles calculations. Further, the nanofiber morphology enhances its mass activity remarkably (by ~20 times) as the diameter is reduced to ~20 nm, attributed to the increased surface area and an unexpected intrinsic activity enhancement due possibly to a favourable eg electron filling associated with partial surface reduction, as unravelled from chemical titration and electron energy-loss spectroscopy. Markedly enhanced oxygen evolution reaction capability is shown when compared to existing catalysts. The mass activity of the ultrafine nanofiber is ~72 times greater than the initial PBC powder catalyst, and 2.5 times greater than the state-of-the-art noble metal-based catalyst (i.e., IrO2). This work not only results in a highly efficient and durable electrocatalyst for OER, which may have important technological implications, but also offers new insight into the development of advanced materials by nanostructure engineering for other applications of energy storage and conversion.

[1] Zhao, B. T., Zhang, L., Zhen, D. X., Yoo, S., Ding, Y., Chen, D. C., Chen, Y., Zhang, Q. B., Doyle, B., Xiong, X. H., Liu, M. L. A tailored double perovskite nanofiber catalyst enables ultrafast oxygen evolution. Nat. Commun. 8, 14586 (2017).