Improvement of capacitance value as the electrode of an electrochemical capacitor by mixing starch with guanidine phosphate

Starch or starch mixed with phosphoric acid, guanidine carbonate, or guanidine phosphate is heat-treated for use as an electrode in an electrochemical capacitor. In the case of starch, the capacitance value is low (31.2 F g−1 at 50 mA g−1). However, the capacitance value significantly increases with the addition of guanidine phosphate, which can act as a flame-retardant (124.1F g−1 at 50 mA g−1). The method used in this study, which involves mixing with a flame-retardant by immersion, should be a promising candidate for improving of the capacitance value of starch-derived carbon.

Graphical abstractThe capacitance value of starch-derived carbon material can be largely improved by the simple preparative method used in this study, that is, mixing with guanidine phosphate before heat treatment.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The carbon material made from starch mixed guanidine phosphate has high capacitance value. ► The simple preparative method (mixing in water and then drying before heat treatment) is effective. ► The percentage of N in this study (ca. 4 wt.%) is small, the capacitance value largely increase. ► The capacitance value of the sample increases by washing with hot water.