The electrochemistry of iron oxide thin films nanostructured by high ion flux plasma exposure
Journal article, 2017

Photo-electrochemical (PEC) water splitting of hematite photoanodes suffers from low performance and efficiency. One way to increase the performance is to increase the electrochemically active surface area available for the oxygen evolution reaction. In this study, we use high ion flux, low energy helium plasma exposure to nanostructure sputtered iron thin films. Subsequent annealing in air at 645 °C leads to the formation of PEC active hematite (?-Fe2O3) phase in these films. The surface area, as derived from electrochemical impedance spectroscopy (EIS), was seen to increase 10–40 times with plasma exposure. The photocurrent density increased by 2–5 times for the plasma exposed films as compared to the unexposed films. However, the less nanostructured film showed a higher photocurrent density. These findings were explained by detailed chemical and structural characterization in combination with electrochemical characterization and attributed to the presence of secondary elements in the film as well as to the presence of secondary iron oxide phases apart from hematite. This work demonstrates the complex effect of plasma exposure on both film morphology and chemical composition of PEC thin films and provides further understanding on how this technique can be used for nanostructuring of other functional films.

Magnetron sputtering


Plasma exposure

Water splitting

Electrochemical impedance spectroscopy


Rochan Sinha

Dutch Institute for Fundamental Energy Research

Irem Tanyeli

Chalmers, Physics, Chemical Physics

Reinoud Lavrijsen

Eindhoven University of Technology

M. C.M. van de Sanden

Dutch Institute for Fundamental Energy Research

Eindhoven University of Technology

Anja Bieberle-Hütter

Dutch Institute for Fundamental Energy Research

Electrochimica Acta

0013-4686 (ISSN)

Vol. 258 709-717

Subject Categories

Other Engineering and Technologies



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