Nitrogen and iodine dual-doped 3D porous graphene as a bi-functional cathode catalyst for Li-O2 batteries

A novel nitrogen and iodine co-doped porous graphene with well-defined hierarchical microstructure is synthesized via a hydrothermal self-assembly strategy followed by heat treatment at elevated temperature. Its electrochemical properties as the cathode catalyst for Li–O2 batteries are investigated. Compared to un-doped, nitrogen or iodine single doped porous graphene, nitrogen and iodine co-doped porous graphene shows much higher activity for oxygen reduction reaction and oxygen evolution reaction. As oxygen cathode for Li–O2 batteries, nitrogen and iodine co-doped porous graphene exhibits an outstanding specific reversible capacity up to 14000 mAh g−1 at 200 mA g−1, a superior high-rate capability (5000 mAh g−1 at 1000 mA g−1), and an excellent cycling stability enduring over 225 cycles with a limited capacity of 1000 mA h g−1 at a current density of 500 mA g−1. The fantastic cycling performance can be attributed to a combination of porous structure and dual-doping, which not only provides a large number of channels for oxygen diffusion and electrolyte infiltration, but also supplies abundant active catalytic sites to affect the formation and decomposition of the discharge products with various morphologies. This study provides an effective approach to develop highly-efficient carbon-based catalysts with optimized pore structure and tunable surface chemistry.