Reactively sputtered ultrathin nickel oxide films for electro-catalytic applications
(2016) 6th International Symposium on Transparent Conductive Materials (IS-TVMs) — Location: Platanias-Chania, Crête - Grèce (9.October.2016)
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- Abstract
- Nickel oxide is a promising electro-catalytic material for the oxygen evolution reaction (OER), for instance in solar water splitting systems. Indeed, it offers a wide band-gap (around 3.2 eV), has a good corrosion resistance when polarised anodically in alkaline media, and upon p-doping obtains a low work function facilitating hole transfer to the water oxidation redox reaction. In practice however, it is difficult to obtain a perfect crystal having the ideal properties to absorb the light and to con vert it into electrochemical energy. The challenge is therefore to produce NiO thin films with a minimum of defects, both inside the bulk crystals and at the grain boundaries. The current presentation will introduce some of our initial results regarding electro-catalytic nickel oxide thin films « 100 nm) deposited by reactive magnetron sputtering on silicon substrates, with the objective to pave the way for the use of NiO thin films in future solar water splitting devices. First of all, as to the deposition process, in-situ internal stress measurements have been performed during reactive sputtering at room temperature with various amounts of oxygen concentration. From the high-resolution data obtained, it was possible to c1early resolve two characteristic deposition regimes, and thus to consider the NiO film as being composed of two sublayers. The first layer, c1osest to the substrate and only about ten nanometers thick,was characterized by a high instantaneous internal stress reaching upto 2,3 GPa at the highest oxygen flow, while the second, outermost layer was deposited almost stress-free. A number of ex-situ characterizations were then carried out, including resistivity measurements, microstructural characterizations (XRD, SEM, TEM) and electrochemical experiments (cyclic voltammetry), with the objective to link the internal stress and hence defect levels in the different films to their electro-catalytic performance for the OER. Our initial results already provide convincing evidence for a clear difference in properties of each of the 2 sub-layers identified by the in-situ measurement, thus helping to determine the optimal NiO film thickness for water splitting applications.
- Affiliations
Technische Universität Darmstadt Institut für Materialwissenschaft
Citations
Poulain, R., Delvaux, A., Klein, A., & Proost, J. (2016). Reactively sputtered ultrathin nickel oxide films for electro-catalytic applications. Proceedings of the 6th International Symposium on Transparent Conductive Materials (TMC-2016), p. 128. https://hdl.handle.net/2078.5/222957