A synthetic strategy for graphitized carbon hollow nanospheres with nano-punched holes decorated with bimetallic selenide as efficient bifunctional electrocatalysts for rechargeable Li–O2 batteries

Abstract

The development of efficient bifunctional electrocatalysts is important for improving the electrochemical performance of Li–O₂ batteries (LOBs). Herein, porous graphitized carbon hollow nanospheres (denoted as PGHs) with nano-punched holes containing suitable defects and minimal amorphous carbon content are developed as highly efficient substrates for loading metal-compound electrocatalysts. For preparing PGH, Fe metal is employed as a nanocatalyst to convert amorphous carbon to graphitic carbon with high electrical conductivity, and nano-punched holes are formed via the selective combustion of amorphous carbon and elimination of Fe metal. PGH possessing nano-punched holes and meso-/macropores facilitates the diffusion of dissolved oxygen and provides sufficient space to store the Li₂O₂ generated during the discharge process. Compared to hollow porous amorphous carbon nanospheres (denoted as PAHs), PGH exhibits a lower overpotential and higher specific capacity. To hybridize with metal selenide, NiFe selenide nanoparticles are uniformly loaded onto PGH (PGH/NiFeSe) via simple impregnation and subsequent selenization. By introducing NiFe selenide, the LOB performances of the hybrid electrode are enhanced compared to those of an electrode comprising PGHs and PAHs. Due to the metal selenide nanoparticles and suitable porous structure of the carbon substrate, PGH/NiFeSe exhibits improved electrochemical performance in LOBs, including reduced polarization, high specific discharge/charge capacity, and stable cycle performance.