Effects of acid dopants on the capacitance of polyaniline by using graphene hydrogels as substrates

Abstract

Three kinds of polyaniline (PANI) doped with hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and perchloric acid (HClO₄) were prepared separately by using graphene hydrogels as substrates, to investigate the influence of anions on the electrochemical properties of PANI for supercapacitors. The structures and polarities of the anions lead to differences in the morphology, oxidation state and crystallinity of PANI. The specific capacitances of the graphene/PANI (GP) composites doped with HCl, H₂SO₄ and HClO₄ are 303.8 F g⁻¹, 464.1 F g⁻¹ and 380.2 F g⁻¹, respectively at a current density of 5 A g⁻¹. The capacitances of the three composites are retained at more than 98% at 70 A g⁻¹. The results exhibit that the acids have a great impact on the specific capacitance of PANI, and GP–H₂SO₄ performs with the highest capacitance.