Understanding the Catalytic Activity of the Preferred Nitrogen Configuration on the Carbon Nanotube Surface and Its Implications for Li–O<sub>2</sub> Batteries
Xiaoping Yi, Xunliang Liu, Ruifeng Dou, Zhi Wen, Wenning Zhou
Abstract
Unraveling the catalytic potential of nitrogen-doped carbon nanotubes (NCNTs) for the electrochemical reaction in a Li–O2 battery (LOB) is of great significance for the preparation of highly active catalysts to overcome the sluggish kinetics. Herein, the surface properties, reaction mechanism, and product behavior on NCNT cathodes are investigated for LOBs using periodic density functional theory. Our calculations demonstrate that the electron-withdrawing nature of N atoms shortens the surrounding N–C and C–C bonds by arranging the electron distribution on the NCNT surface. The conversion from the p-type semiconductor to n-type semiconductor or metallic characteristics occurs between pristine CNTs (PCNTs) and NCNTs. Surprisingly, NCNTs exhibit enhanced adsorption for LixOy in comparison with PCNTs. The lithiation reaction is the primary contributor to the formation of Li2O2 and Li2O on the surfaces of both PCNTs and NCNTs. Meanwhile, tri-N and tetra-N NCNTs promote the growth of Li2O2 and inhibit the further reduction of Li2O2 to Li2O, alleviating the passivation of the cathode surface. Our study achieves a deeper understanding of the catalytic mechanism of NCNTs and provides hints for the design of high-efficiency catalysts for Li–O2 and other potential batteries.