Existence of nearest-neighbor and variable range hopping in Pr$_2$ZnMnO$_6$ oxygen-intercalated pseudocapacitor electrode

TL;DR

This study characterizes Pr$_2$ZnMnO$_6$'s structure, conduction mechanisms, and pseudocapacitive behavior, revealing two conduction regimes and promising electrochemical performance for energy storage applications.

Contribution

It demonstrates the coexistence of nearest-neighbor and variable range hopping conduction mechanisms in Pr$_2$ZnMnO$_6$, and explores its pseudocapacitive properties as an electrode material.

Findings

Identification of NNH and MVRH conduction mechanisms below 580 K.

PZM exhibits a specific capacitance of 69.14 F/g.

Oxygen vacancies influence electrical and electrochemical behavior.

Abstract

X-ray diffraction pattern and Raman spectrum authenticate the monoclinic P21/n structure of polycrystalline Pr$_2$ZnMnO$_6$ (PZM) synthesized by the solid-state reaction technique. The X-ray photoemission spectrum suggests the existence of oxygen vacancy in PZM, which plays a crucial role in electrical conduction as well as in electrochemical behavior. The existence of two different conduction mechanisms (such as nearest-neighbor hopping (NNH) and Mott variable range hopping (MVRH)) is observed from the investigation of dc conductivity studies, dielectric relaxation, and impedance analysis of PZM. It is found that below 580 K, there is a transition from NNH to MVRH due to the decrease of activation energy. The constant phase element model is used to correlate the Nyquist plot and electric modulus of PZM. The bulk PZM electrode exhibits intercalated pseudocapacitive nature which offers an efficient specific capacitance of 69.14 F/g at a charge and discharge currents of 2 A/g in an aqueous solution of 1 M KOH. The charge storage mechanism of the PZM electrode has been analyzed and discussed.