Multiscale Bi/Bi₂O_3-x Mott-Schottky heterojunction confined in hierarchical mesoporous carbon for advanced aqueous...

Bi₂O₃ emerges as a promising alkaline battery anode material due to its high theoretical capacity (380 mAh g^-1) and reversible Bi³⁺/Bi⁰ redox chemistry. However, persistent challenges including insufficient active site exposure and low intrinsic conductivity result in actual capacities falling short of theoretical value. Multiscale Bi/Bi₂O_3-x Mott-Schottky heterostructures confined within mesoporous carbon networks (Bi/Bi₂O_3-x@C) are constructed through the controlled pyrolysis of Bi-metal-organic-farmwork (Bi-MOF) sacrificial template. The established Mott-Schottky interface between metallic Bi and semiconducting Bi₂O_3-x effectively modulates charge distribution through built-in electric fields and lower the OH^- absorption energy to -3.98 eV, while the mesoporous carbon confinement architecture simultaneously enhances particle dispersion and enables rapid mass transfer kinetics. The optimized Bi/Bi₂O_3-x@C anode demonstrates exceptional electrochemical performance with high specific capacity (172.2 mAh g^-1 at 1 A g^-1), and outstanding rate capability (90% retention at 4 A g^-1) in 1 M KOH. The enhanced energy-storage performance is attributed to the synergistic effects of tunable Bi domain sizes and oxygen vacancy concentrations, which facilitate efficient ion diffusion pathways, as well as hierarchical porosity that ensures structural integrity during cycling.