The modulation of adsorption balance effect for promoting selenium cathode redox reaction kinetics in aqueous zinc-selenium battery

Aqueous zinc-selenium (Zn-Se) battery shows promising applications because of its inherent safety and high theoretical capacity. However, the slow redox reaction kinetics of Se cathode limit its development. The strategy of designing functional catalytic host materials with suitable adsorption ability is essential to promote Se redox reaction kinetics. We construct a catalytic host material consisting of axially oxygen-coordinated Cu single atoms and neighboring Cu atomic clusters (Cu-N₄O/Cu_ACs) to probe its modulation mechanism of suitable adsorption ability on Se redox reaction. The Cu-N₄O/Cu_ACs enable the aqueous Zn-Se battery to exhibit a specific capacity of 643 mAh g^–1 at 0.2 A g^–1 and fast Se redox reaction kinetics. Experimental characterization and density functional theory confirm the “adsorption balance effect” of Cu-N₄O/Cu_ACs. The neighboring Cu_ACs can enhance the adsorption ability for Se species. The axially coordinated O atoms can promote electron delocalization and downshift d-band center, weakening the excess adsorption ability brought by Cu_ACs and lowering the energy barrier of redox reaction. The adsorption balance effect between clusters of Cu_ACs and axial O atom causes Cu-N₄O/Cu_ACs to exhibit excellent catalytic effect. This work gives new insights for the optimization of the catalytic behavior between the adsorption ability of SACs and redox reaction kinetics in aqueous Zn-Se battery.