Determination of the Critical Points for Intercalating Systems by the EMF Method Concerning Foreign Metal

Abstract

The work is devoted to the study of the possibility of determining the critical points of phase diagrams by measuring the EMF of electrochemical cells relative to a metal that is not part of the test substance. The measurement results of the concentration dependences of the EMF for the Cu x TiS 2 system in the electrochemical cells Na|Na + |Cu x TiS 2 and Cu|Cu + |Cu x TiS 2 in the concentration range 0 < x < 0.7 are compared. It was determined that the chemical potential of the ion is independent of x in a satisfactory approximation. The EMF difference in the given cells is close to the standard electrode potentials difference for respective metals. It is concluded that the dependences E(x) for both types of cells are similar and correlated. Therefore, one can choose any convenient metal for measurements of this kind. Using the example of measuring EMF in electrochemical cells for the Fe x TiSe 2 system concerning sodium and lithium, we showed that the elastic contribution to free energy is constant over the entire concentration range 0 < x < 0.5.

Electronic Structure of VxTi1–xSe2 Solid Solutions with the (V,Ti)Se2 Structural Fragments

“…This indicates an increase in the Fermi energy of the material. A plateau is observed in the V concentration range of 0.3 < x < 1.0, which indicates the constancy of the Fermi energy. − The EMF also suggests that we can assume a single-phase solid solution for x < 0.2 and a mixture of two phases for x > 0.3.…”

“…Electromotive Force. The results of EMF measurements, which highlight changes in the electronic structure of the V x Ti 1−x Se 2 system analyzing the E ∼ f(x) dependence, 52,53 are shown in Figure 9.The EMF monotonically decreases with the decrease in the V concentration in the range of 0 < x < 0.2. This indicates an increase in the Fermi energy of the material.…”

Janus Layers in the TiSe2–TiS2 System

“…However, this behavior cannot be considered as evidence of the presence of a few phases in the material, because in our case the EMF of the Li/Li + /Ti­(Se 1– x S x ) 2 /Pt cell is measured relative to a metal (Li) that is not included in the chemical formula of the studied material. Therefore, the EMF results do not indicate a change in the chemical potential of atoms, but only a change in the chemical potential of electrons . The plateau can indicate both the multiphase state and the electronic structure features, such as, for example, the formation of a band of localized states around the Fermi level.…”

“…Therefore, the EMF results do not indicate a change in the chemical potential of atoms, but only a change in the chemical potential of electrons. 27 The plateau can indicate both the multiphase state and the electronic structure features, such as, for example, the formation of a band of localized states around the Fermi level. The reported data, 4,20,28−31 however, did not confirm the latter assumption.…”

Effect of Cobalt on Structural and Electrochemical Properties of the TiSe2 System and Its Sodiation

“…The determination of phase boundaries using an electromotive force (EMF) method is based on measuring the potential difference between the Na n Co x TiSe 2 electrode under study and the sodium reference electrode. The position of the Fermi level is known to be related to the electronic structure of the material, as well as the electrochemical potential of the system. − Sodium metal has a constant potential and is used as a counter and reference electrode. During sodium intercalation in Co x TiSe 2 , the sodium atoms bring electrons into the system, changing its Fermi level; as a result, the difference between the Fermi levels of the metallic sodium and the investigated Na n Co x TiSe 2 system decreases.…”