In this talk, we will show our recent results dealing with vanadium (VN) and tungsten nitride (WN) thin films deposited by MS on silicon wafers. During the last ten years, transition metal nitride[3–5] have been investigated as an attractive pseudocapacitive electrode. In the frame of this study, the nitride thin films have been proposed as an efficient bi-functional material acting not only as the pseudocapacitive electrode but also as a suitable current collector. Structural, electrical and electrochemical properties have finely tuned according to the synthesis parameters to reach the best performance.
Advanced characterization technique such as operando X-Ray Absorption Spectroscopy (XAS) was performed on these nitride layers to monitor the change of the oxidation state occurring at the metal centers at the V K-edge and W L3-edge when cycling in different electrolytes (KOH, LiOH…). Operando XAS spectra were acquired at ROCK beamline (SOLEIL synchrotron, France) using the quick-XAS channel-cut Si (111) monochromator with a frequency oscillations of 2 Hz, corresponding to 15 spectra for a whole cycle. Surface analysis (X-Ray Photoelectron Spectroscopy – XPS) coupled with Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) were used to evaluate the chemical composition and to study the change of the oxidation state of the transition metal at different etched depth. Finally, based on the optimized nitride layers, symmetric MSC in parallel plates or interdigitated topologies were fabricated using microfabrication technique and tested in aqueous electrolytes.
References
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[2] N. A. Kyeremateng, T. Brousse, D. Pech, Nat. Nanotechnol. 2016, 12, 7.
[3] D. Choi, G. E. Blomgren, P. N. Kumta, Adv. Mater. 2006, 18, 1178.
[4] R. Lucio-Porto, S. Bouhtiyya, J. F. Pierson, A. Morel, F. Capon, P. Boulet, T. Brousse, Electrochim. Acta 2014, 141, 203.
[5] P. Pande, P. G. Rasmussen, L. T. Thompson, J. Power Sources 2012, 207, 212.
Acknowledgments: The authors want to thank the French network of the electrochemical energy storage (RS2E) for this support. The French RENATECH network is greatly acknowledged.