TM-N4C (TM = Co, Pd, Pt and Ru) as OER electrocatalysts in lithium-oxygen batteries: First-principles study

Recently, atomically dispersed transition metal-N4-doped graphene electrocatalysts have attracted tremendous interests due to their advantages of exposed active sites, large surface/volume ration, nanoscale thickness and porous morphology. To evaluate the catalytic performance of transition metal-N4-doped graphene as electrocatalysts for oxygen evolution reaction of lithium peroxide in lithium-oxygen batteries, four catalysts formulated as TM-N4C (TM = Co, Pd, Pt and Ru) have been studied from first-principles calculations. The formation energies show that the four catalysts are energetically stable. At the equilibrium voltage, the Pt-N4C has the smallest charging overpotential of 0.02 V, followed by the Pd-N4C (0.09 V) and Co-N4C (0.12 V), which suggests that the Pt-N4C can be a promising catalyst for the oxidation of lithium peroxide. However, the optimal configurations of the Li2O2 and LiO2 molecule adsorbed on the Ru-N4C show that the OO bond breaks and the Ru-O bond forms, which is further evidenced by the electronic structure analysis and difference charge density, indicating that the Ru-N4C catalyst is too active to be conducive to the oxygen evolution reaction of lithium peroxide.