An Unexpected Electrochemical Performance Enabled by In Situ Formed Quasi-Metal-Semiconductor Heterojunction with Innumerous P-Type Anti-Barrier Layer

摘要

Nickel/cobalt-based materials with diffusion-controlled redox reactions haveshown potential as the battery-type electrode for battery-supercapacitorhybrid devices. However, the sluggish redox kinetics and poor structuraldurability greatly restrict the rate capability and cycling lifespans of thesematerials to match up with activated carbon electrodes. Herein, an in situsplit quasi-metal-semiconductor (CoO-Ni_3N) heterostructure is constructedvia a simple hydrothermal reaction, delivering a superior areal capacitance of≈3800 mF cm~(?2) (≈sevenfold higher than bare CoO and Ni_3N) and top-levelcycling performances (32 000 cycles with ≈98% retention) among the batterytypematerials in supercapacitors. The P-type anti-barrier layer formed at theCoO-Ni_3N heterostructure interface with a sufficiently large depletion width,effectively optimizes the electron structures and OH? adsorption abilities ofbuilding blocks. In situ Raman and various ex situ characterizations uncoverthat the CoO-Ni_3N heterostructure undergoes different redox routes withenhanced reversibility and kinetics compared to building blocks, which areresponsible for the improved capacitance and rate performance. Based on thedesigned electrode, the assembled device shows rare rate performance andcycling lifespans in the context of previous reports. The work unravels therole of heterojunctions in semiconductor theory and may extend to heterostructuredesign in other electrochemical energy storage fields.