Fabrication of solid-state supercapacitors
Polyvinyl alcohol (PVA)/sulfuric acid (H2SO4) electrolyte was
prepared by adding PVA power (6 g) into H2SO4 aqueous
solution (6 g H2SO4 into 60 ml deionized water). The whole
mixture was heated to 85 1C under vigorous stirring until the
solution became clear, then the solution was kept at 85 1C
without stirring for about 1 h. After cooling down, two
graphite/polyaniline paper (G/PANI-Paper) electrodes were
immersed into the PVA/H2SO4 electrolyte for 5 min and then
were assembled into a supercapacitor by sandwiching a
cellulose membrane (TF44, NKK, Japan) as a separator
between them. For the planar interdigital structure, electrolyte
was coated onto the interdigital electrodes and no
separator was needed. Then the devices were left in an
electrical oven at 45 1C for about 4 h to vaporize the
excess water.