Electrochemical morphology reconstruction induced crystalline-amorphous La-Al oxide heterojunctions for advanced supercapacitor electrodes

Driven by the global push for sustainable energy, supercapacitors are regarded as competitive energy storage systems. Nevertheless, boosting their energy density and cycling durability remain core challenges. Herein, a La 2 O 3 /Al 2 O 3 heterostructure (La-Al-O) is in-situ fabricated on nickel foam (NF) via a hydrothermal route. Electrochemical activation converts crystalline La 2 O 3 into amorphous La 2 O 3 , triggering structural reconstruction: interwoven nanosheet networks evolve into loose, crumpled nanosheets. This transformation enriches oxygen vacancies and generates Ni(OH) 2 on NF to create abundant ion-accessible active sites, while Al 2 O 3 serves as a structural stabilizer against framework collapse (activated La-Al-O, abbreviated A-La-Al-O). In terms of electrochemical performance, the A-La-Al-O/NF electrode exhibited a high specific capacitance of 4.60 F·cm −2 at a current density of 5 mA·cm −2 . After 20,000 cycles at a scan rate of 20 mA·cm −2 , the cycle retention rate was 75.7%. For the assembled asymmetric device (denoted as A-La-Al-O/NF/activated carbon (AC)), an energy density of 49.41 Wh·kg −1 was achieved at a power density of 889.38 W·kg −1 , with a cycle retention rate of 82.5% after 20,000 cycles. This study adopts method combining hydrothermal and electrochemical activation without the need for binders, featuring a simple and convenient process. It provides a new insight for the high-value utilization of rare earths and the development of high-performance supercapacitors.