Surface Electronegativity as an Activity Descriptor to Screen Oxygen Evolution Reaction Catalysts of Li-O2 Battery

The development of active electrocatalysts for enhancing Li2O2 decomposition kinetics plays an important role in reducing the overpotential of Li-O-2 batteries. However, a catalytic descriptor is not established due to the difficult characterization of the charge transfer between Li2O2 and the catalyst. Here, we employ first-principles thermodynamic calculations to study the electrocatalytic mechanism of 4d transition metals. We found that charge acceptation and donation capacities of catalysts, defined as surface electron affinity (V-SEA) and surface ionic potential (V-SIP), take cooperative responsibilities for the activation of Li-O-2 bonds and the reduction of desorption barriers of Li+ and O-2, respectively. Therefore, we define surface electronegativity V-SE (V-SE (V-SEA + V-SIP)/2), which exhibits a volcano curve with a reduced charge overpotential, as the catalytic descriptor. We identified those catalysts with surface electronegativities of 1.7-2.2 V to have highly catalytic activities in the reduction of the charge overpotential, which are well verified by previous experimental data. The present study opens a wide avenue in the development of high-activity catalysts for interfacial electrocatalysts by an effective descriptor.