Insights into Perovskite Nano-Catalysts as Oxygen Electrodes for the Electrochemical Splitting of Water

In recent years, electricity-driven hydrogen production by electrochemical splitting of water has received particular attention because of its potential applicability in decentralized energy storage concepts.(1)  Most of the efforts have been focused on the electrochemical reaction occurring at the anode side, the oxygen evolution reaction (OER), since it is source of large overpotentials.(2)

Advances in computational studies and in in situ characterizations can now offer novel insights into the OER mechanism, revealing new perspective in the search for advanced materials. However, at present most of the fundamental studies on OER catalysts have been conducted using bulk techniques and materials with low surface area, which is a questionable approach considering that the OER is a near-surface reaction. In this study,(3) we couple a cutting-edge synthesis method to produce highly active OER nano-catalysts with time resolved X-ray absorption spectroscopy (XAS) measurements able to capture dynamics of the catalyst electronic and local structure during operando conditions. The use of nano-catalysts not only allows achieving outstanding performance, but also reveals electronic and structural changes at the catalysts surface (given the high surface to bulk ratio of nanoparticles) never observed before. Particularly, we could demonstrate that the key for highly active catalysts is a self-assembled, (oxy)hydroxide top layer. This is completely different from the message of several water electrolysis-related publications, which consider the surface of oxide catalysts as an ideal, atomically flat surface. This new concept completely revolutionizes the currently most accepted view of design principles for highly active perovskite catalysts. It also points towards the paramount necessity of investigating other perovskite properties under operando conditions in order to develop accurate design principles for highly active perovskite catalysts.(4)
 
 
 1.       Fabbri E, Habereder A, Waltar K, Kotz R, Schmidt TJ., Catal Sci Technol 2014, 4: 3800-3821.
2.        Fabbri E, Nachtegaal M, Cheng X, Schmidt TJ, Advanced Energy Materials 2015, 5(17) 1402033.
3.       Fabbri E, Nachtegaal M, Cheng X, Binninger T, Durst J, Bozza F, et al., Nature Materials 2017, 16: 925–931
4.      Fabbri E, Abbott DF, Nachtegaal M, Schmidt TJ, Current Opinion in Electrochemistry 2017, https://doi.org/10.1016/j.coelec.2017.08.009

Bio: Emiliana Fabbri received her PhD in Materials Science from the University of Rome Tor Vergata, Italy on December 2008. A significant part of her PhD studies were carried out at the University of Florida, Gainesville USA. In 2009 she was appointed as tenure scientist at the International Center for Material Nanoarchitectonics (MANA) at the National Institute for Materials Science (NIMS), Japan. Emiliana Fabbri deeply investigated proton and oxygen-ion conduction mechanism in bulk oxides and electrochemical reaction mechanisms, particularly related to solid oxide fuel cells.  Since January 2012, Emiliana Fabbri joined the Paul Scherrer Institute in Switzerland as senior scientist working on materials for electrochemical energy storage and conversion, with emphasis on metal oxides. To gain a fundamental understanding of electrochemical reaction mechanisms and catalytic activity descriptors, she is particularly interested in the catalyst surface chemistry and electronic structure investigated by operando X-ray photoelectron spectroscopy and X-ray absorption spectroscopy, respectively.