Capacitive charge storage mechanism in sanmartinite to be determined by qualitative and quantitative electrochemical analysis

Abstract

Pseudocapacitive behavior is one of the most concerned basic scientific issues in the electrochemical field. How to distinguish capacitive, pseudocapacitive and battery behavior accurately remains as a difficult problem. In addition, the capacitive charge storage mechanism of the non-Faraday process has been found in non-carbon-based materials in ways that challenge established theory. This is also the difficulty in defining the electrochemical behavior of newly discovered materials. Here, we report the pseudocapacitance behavior of sanmartinite (ZnWO4) for the first time. Under aqueous system conditions, the cyclic voltammetry curves of ZnWO4 present the ideal rectangle shape, and the galvanostatic charge/discharge curves exhibit the isosceles triangle shape. In addition, the calculated value of b is 0.88, which further indicates that the kinetic process is controlled by the surface capacitance.