In situ encapsulation engineering boosts the electrochemical performance of highly graphitized N-doped porous carbon-based copper–cobalt selenides for bifunctional oxygen electrocatalysis

Abstract

Transition-metal selenides are gaining prominence as promising electrode materials for energy storage applications owing to their low electronegativity and environment-friendliness compared with metal sulfides/oxides. Herein, a CuCoSe@NC nanocomposite with copper–cobalt selenides embedded in highly graphitized N-doped porous carbon was synthesized by an in situ encapsulation strategy with metal–organic framework crystals (CuCo-BDC) as templates followed by selenization, and used as a bifunctional electrocatalyst for Zn–air batteries in lye. The result shows that the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activity of the optimal CuCoSe@NC-2 was enhanced, and the assembled Zn–air batteries exhibited a remarkable electrochemical performance with the use of the CuCoSe@NC-2 electrode, including a high power density (137.1 mW cm⁻²) and excellent charge–discharge cycling stability, which were better than those of the Pt/C + RuO₂ electrocatalyst. Such improvement is attributed not only to the higher porosity and larger specific surface area (342 m² g⁻¹) of the carbon matrix, which increased the contact area with oxygen-containing species, but also the encapsulation effect of the highly graphitized N-doped carbon layer and the high content of pyridine-N species also further improved the conductivity of selenide composites. This work has introduced N-doped bimetallic selenides as an ideal candidate for bifunctional electrocatalysts.