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

Transition-metal selenides are capturing eminence as promising electrode materials for energy storage applications owing to their low electronegativity and environment-friendly 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 the in-situ encapsulation strategy with metal-organic framework crystal (CuCo-BDC) as templates followed by selenization, and used as bifunctional electrocatalysts 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 remarkable electrochemical performance with the use of CuCoSe@NC-2 electrode, including high power density (137.1 mW cm-2) and excellent charge-discharge cycle 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.