Nickel incorporation engineering for synergistic regulation of oxygen vacancies and electronic band configuration in Bi2O3 nanosheets for high-performance supercapacitor electrodes

Nanostructured bismuth oxide (Bi 2 O 3 ) holds great potential as a supercapacitor electrode material, owing to its high theoretical specific capacitance (1370 F g −1 ), low cost, and environmental benignity. Nevertheless, the capacitance of conventional Bi 2 O 3 is severely constrained by its inherently poor electrical conductivity and inferior redox activity. Herein, a nickel (Ni 2+ )-incorporation strategy enables the precise modulation of oxygen vacancies and energy band configurations of Bi 2 O 3 nanosheets, leading to significantly enhanced electrical conductivity and redox activity. Experimental characterizations demonstrated that an optimized Ni 2+ incorporation concentration of 1.00 mol% in Bi 2 O 3 nanosheets facilitated the formation of “active oxygen vacancies” (with unpaired electrons), a phenomenon rarely observed previously. In-depth mechanism discussions via energy band structure analysis and density functional theory (DFT) calculations further verified that Ni 2+ incorporation: (i) refines the electronic band structure; (ii) lowers the oxygen vacancy formation energy (thus facilitating their generation); and (iii) enhances the surface adsorption energy of OH − to optimize the adsorption-desorption process of OH − on the Ni-incorporated Bi 2 O 3 surface. Consequently, the optimal (Ni/Bi) 0.10 -Bi 2 O 3 electrode (corresponding to 1.00 mol% Ni 2+ incorporation) delivers a remarkable specific capacitance (836 F g −1 at 1 A g −1 , ~3 times that of pristine Bi 2 O 3 ) and exhibits favorable charge-discharge cycling stability (>80% capacitance retention and approximately 100% coulombic efficiency after 5000 cycles). This work establishes a feasible incorporation strategy for optimizing metal oxide electrodes and provides valuable insights into oxygen vacancy engineering to advance next-generation supercapacitors.