Effects of silico-tungstic acid on the pseudo capacitive properties of manganese oxide for electrochemical capacitors applications

In this work manganese oxide (MnO₂) is modified with silico-tungstic acid (STA). Three samples are synthesized by the co-precipitation method. The powders obtained after elaboration are characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) imaging coupled to Electron Dispersive Spectroscopy (EDS) analysis and Brunauer-Emmet-Teller (BET) for their surface area determination. The effect of the modification of the manganese oxide with STA on its surface is determined. It is shown that MnO₂ modified with STA exhibits better cumulative high specific surface areas and mesoporous volumes areas. For example, the sample fabricates with 10% STA (MnO₂ – 10% STA) has a BET surface area of 153.6 ​m² ​g⁻¹ and volume area 0.92 ​cm³ ​g⁻¹ whereas the sample without STA (MnO₂ – 0% STA) has a surface area of 132.57 ​m² ​g⁻¹ and a mesoporous area of 0.26 ​cm³ ​g⁻¹. The electrochemical performance analysis of the different working electrodes prepared for super-capacitors applications is carried out using cyclic voltammetry (CV)., using a solution of 0.5 M K₂SO₄ as an electrolyte in potential range of −0.4 and 0.9 ​V at a sweep speed of 10 ​mV/s. The CV results are correlated to those of the BET surface and mesoporous areas values Accordingly, it is shown that samples spiked with STA exhibit higher electrochemical double layer capacitance than those of none modified with STA. These measurements respectively give 38 ​F ​g⁻¹, and 181 ​F ​g⁻¹ for MnO₂ without STA (MnO₂ – 0% STA), and MnO₂ modified with 10% STA (MnO₂ – 5% STA).