Can Li Atoms Anchored on Boron and Nitrogen Doped Graphene Catalyze Dinitrogen Molecule to Ammonia? A DFT Study.

Abstract

Most successful electrochemical conversion of ammonia from dinitrogen molecule reported to date is Li mediated mechanism. In the framework of the above fact and that Li anchored graphene is an experimentally feasible system, the present work is a computational experiment to identify the potential of Li anchored graphene as a catalyst for N2 to NH3 conversion as a function of (a) minimum number of Li atoms needed for anchoring on graphene sheets and (b) role of chemical modification of graphene surfaces. Li anchored graphene sheets are potential catalysts for ammonia conversion with preferential adsorption of N2 through end-on configuration on Li atoms anchored on doped and pristine graphene surfaces. This mode of adsorption being characteristic of Nitrogen Reduction Reaction (NRR) through enzymatic pathway, examination of the same followed by analysis of electronic properties demonstrates that tri-Li atoms (Tri Atom Catalysts, TACs) are more efficient as catalysts for NRR as compared to two Li atoms (Di Atom Catalysts, DACs). Either way, the rate determining step was found to be *NH2 → *NH3 step (mixed pathway) with ∆Gmax = 1.02 eV and *NH2-*NH3→ *NH2 step (enzymatic pathway) with ∆Gmax = 1.11 eV for 1B doped TAC and DAC on graphene sheet, respectively.