Enhancing Energy Storage via Confining Sulfite Anions onto Iron Oxide/Poly(3,4-Ethylenedioxythiophene) Heterointerface

Multiple oxidation-state metal oxide has presented a promising charge storage capability for aqueous supercapacitors (SCs); however, the ion insert/deinsert behavior in the bulk phase generally gives a sluggish reaction kinetic and considerable volume effect. Herein, iron oxide/poly(3,4-ethylenedioxythiophene) (Fe₂O₃/PEDOT) heterointerface was constructed and enabled boosted Faradaic pseudocapacitance by dual-ion-involved redox reactions in Na₂SO₃ electrolytes. The Fe₂O₃/PEDOT interface served as a “bridge” to couple electrode and anion SO₃^2- and exhibited a strong force and stable bonding with SO₃^2-, thus providing an additional Faradaic charge storage contribution for SCs. Significantly, the PEDOT-capsulated Fe₂O₃ nanorod array (Fe₂O₃@PEDOT) electrode presented a specific capacitance of 338 mF cm^-2 at 1 mA cm^-2 with 1 M Na₂SO₃ electrolyte, which was twice that of the pristine Fe₂O₃ nanorod electrode. The boosted interfaced Faradaic reaction of SO₃^2- partially hindered the intercalation of Na⁺ in the Fe₂O₃ bulk phase, efficiently favoring the electrochemical stability. © 2023 American Chemical Society.