Abstract
Iron is unstable as an oxygen evolution electrode in alkaline media. Thus, relatively expensive nickel-based electrodes are used in industrial alkaline water electrolysis. We show that an iron substrate can be rendered stable and electrocatalytically active for the oxygen evolution reaction by nano-scale surface modification with nickel. The electrocatalytic activity of such a surface-modified iron electrode is comparable to the recently-reported nickel-based catalysts. The electrocatalytic activity is due to a 50-nanometer layer of a high-surface area α-nickel hydroxide on the iron electrode. The nickel modification renders the iron electrode electrically-conductive, prevents dielectric breakdown, and thus endows anodic stability. The electrocatalytic activity is unchanged even after 1000 hours of continuous operation. The temperature of preparation is critical, as excessive dehydration of the hydroxide layer results in nickel ferrite formation and a drastic reduction in electrocatalytic activity. We report significant insight into the surface chemical composition and structure of the catalyst layer by X-ray Absorption Spectroscopy, Photoelectron Spectroscopy, and Transmission Electron Microscopy. Electrochemical kinetics analysis suggests that surface hydroxo-intermediates react with the hydroxide ions from the solution to evolve oxygen. Thus, the surface-modified iron substrates present an opportunity for improving the performance and reducing the cost of alkaline water electrolysis systems.
| Original language | English |
|---|---|
| Pages (from-to) | F392-F400 |
| Journal | Journal of the Electrochemical Society |
| Volume | 165 |
| Issue number | 5 |
| DOIs | |
| State | Published - 2018 |
Funding
The research reported here was supported by the Loker Hydrocarbon Research Institute, and the University of Southern California (USC). We thank Dr. Aswin Manohar and Dr. Chenguang Yang for support with materials and test procedures, and Dr. A. Sundar Ra-jan for help with the graphics. The TEM samples were prepared at UCLA’s Nanolab with the assistance of Noah Bodzin. The TEM imaging and analysis, along with the XPS data, was acquired at USC’s Center for Electron Microscopy and Microanalysis (CEMMA). X-ray absorption studies at Sector 20 used resources of the Advanced Photon Source, a U. S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. We acknowledge Dr. Qing Ma and Denis Keane of DND-CAT for sharing the bent Laue optic.