Computer Simulation Study of Lithium and Oxygen Adsorption on Ruthenium Dioxide (110) Surface

Abstract

Metal oxides are widely considered as excellent catalysts in lithium-air batteries to promote the production of stable discharge products and achieve superior electrochemical performance. The lithium–air (Li–air) battery is a metal–air electrochemical cell or battery chemistry that uses oxidation of lithium at the anode and reduction of oxygen at the cathode to induce a current. Despite various studies exploring the use of metal oxides as effective catalysis, the catalytic activity of ruthenium oxide (RuO2) towards lithium and oxygen ions is not fully understood. In this work, we investigate the adsorptions of lithium and oxygen on the RuO2 (110) surface using density functional theory (DFT) method. Due of the size of the supercell, and assuming that oxygen atoms occupy bulk-like positions around the surface metal atoms, only five values of (gamma) Γ are possible if constraint to a maximum of 1 monolayer (ML) of adatoms or vacancies: Γ= 0 surface is the stoichiometric surface, Γ= 1, 2 are the partially and totally oxidised surfaces, and Γ=-1, -2 are the partially and totally reduced surfaces. The addition of two oxygen atoms revealed the most stable adsorption energy is the mono-clear followed by bridging configuration. The lithium orientation between two bridging oxygen and in plane oxygen (bbi) orientation is much more stable, thus lithium generally prefers to adsorb where it will be triply coordinated to two bridging oxygen atoms and one in plane oxygen atom. Rutile RuO2 has been widely considered as an excellent catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in non-aqueous.