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) (Fe 2 O 3 /PEDOT) heterointerface was constructed and enabled boosted Faradaic pseudocapacitance by dual-ion-involved redox reactions in Na 2 SO 3 electrolytes. The Fe 2 O 3 /PEDOT interface served as a “bridge” to couple electrode and anion SO 3 2– and exhibited a strong force and stable bonding with SO 3 2–, thus providing an additional Faradaic charge storage contribution for SCs. Significantly, the PEDOT-capsulated Fe 2 O 3 nanorod array (Fe 2 O 3 @PEDOT) electrode presented a specific capacitance of 338 mF cm –2 at 1 mA cm –2 with 1 M Na 2 SO 3 electrolyte, which was twice that of the pristine Fe 2 O 3 nanorod electrode. The boosted interfaced Faradaic reaction of SO 3 2– partially hindered the intercalation of Na + in the Fe 2 O 3 bulk phase, efficiently favoring the electrochemical stability.