Defect-engineered yttrium orthoferrite for high-energy aqueous supercapacitors

Defect engineering in orthorhombic perovskite oxides enables tunable electrochemical functionality through lattice–defect–charge coupling. Nanoporous yttrium orthoferrite (YFeO3) synthesized via a sol-gel route exhibits controlled octahedral tilting and oxygen vacancies, enabling reversible Fe3+/Fe2+ redox transitions and extending the electrochemical stability window to 2.4 V in neutral 0.5 M Na2SO4 (aq). The YFeO3 electrode delivers a specific capacitance of 216 F g−1 at 1 A g−1 and an energy density of 43 Wh kg−1 at 1200 W kg−1, retaining 91% capacitance after 10 000 galvanostatic charge–discharge cycles. Linear sweep voltammetry confirms suppression of hydrogen and oxygen evolution through defect-mediated modulation of surface electronic states. These results identify YFeO3 as a promising high-voltage aqueous electrode. Moreover, defect–tilt coupling within the Pnma lattice emerges as a general design principle for stabilizing redox-active perovskite oxides in aqueous energy-storage systems operating at extended voltages.