Electrochemical activation of molecular nitrogen at the Ir/YSZ interface

Abstract

Nitrogen is often used as an inert background atmosphere in solid state studies of electrode and reaction kinetics, of solid state studies of transport phenomena, and in applications e.g. solid oxide fuel cells (SOFC), sensors and membranes. Thus, chemical and electrochemical reactions of oxides related to or with dinitrogen are not supposed and in general not considered. We demonstrate by a steady state electrochemical polarisation experiments complemented with in situ photoelectron spectroscopy (XPS) that at a temperature of 450 1C dinitrogen can be electrochemically activated at the three phase boundary between N 2 , a metal microelectrode and one of the most widely used solid oxide electrolytes-yttria stabilized zirconia (YSZ)-at potentials more negative than E = À1.25 V. The process is neither related to a reduction of the electrolyte nor to an adsorption process or a purely chemical reaction but is electrochemical in nature. Only at potentials more negative than E = À2 V did new components of Zr 3d and Y 3d signals with a lower formal charge appear, thus indicating electrochemical reduction of the electrolyte matrix. Theoretical model calculations suggest the presence of anionic intermediates with delocalized electrons at the electrode/electrolyte reaction interface. The ex situ SIMS analysis confirmed that nitrogen is incorporated and migrates into the electrolyte beneath the electrode.

Combining high temperature electrochemistry and time of flight secondary ion mass spectrometry: Quasi in situ study of lanthanum strontium chromate manganate electrodes

“…It is in line with previous studies on the spectroscopic/microscopic analysis of solid state electrodes in operation, i.e. under kinetic load, primarily in the system Pt(O 2 )/YSZ [20e23] and Ir(N 2 )YSZ [24], but recently also in perovskite-based cathodes [4,6]. We would like to point out that ex situ SIMS has been applied quite successfully to image fast reaction sites of gas electrodes e.g.…”

Adsorption of nitrogen and ammonia at zirconia surfaces

“…Furthermore the calculated N 1s core level energies of the adsorbate were compared to those of gas-phase N 2 , N 2 À and N 2 2À in order to gain further insight into the oxidation state of the adsorbed N 2 species. The core level energies of the adsorbate shift by about +2 eV which is similar to the value found for gas-phase N 2 À when diffuse Rydberg orbitals were added to the nitrogen basis set and also to a recent experimental work where a core level shift of +2.3 eV has been found [26]. The corresponding shift of gas-phase N 2 2À (+3.6 eV) is considerably larger.…”

“…Recently, the mechanism of nitrogen incorporation has been studied electrochemically [6,26,27]. It was found that the incorporation proceeds in several well-defined steps each connected with electron transfer from the yttrium-doped zirconia electrode to N 2 .…”

Impedance spectroscopy study of the unipolar and bipolar resistive switching states of atomic layer deposited polycrystalline ZrO2 thin films

“…The N1 s spectrum shown in Fig. (d) contains two components, one peak at 401.8 eV related to a covalent N 2 , and an additional peak at 398.8 eV which can be attributed to nitrogen ionic species, as for example N 2 2− with a binding energy of 398.5 eV . As the measurement was done from the film's depth, one has to consider the possibility of residual ionic nitrogen species in the films, which might segregate at the grain boundaries .…”

“…with a binding energy of 398.5 eV [56]. As the measurement was done from the film's depth, one has to consider the possibility of residual ionic nitrogen species in the films, which might segregate at the grain boundaries [57].…”