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-O2 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 (VSEA) and surface ionic potential (VSIP), take cooperative responsibilities for the activation of Li-O2 bonds and the reduction of desorption barriers of Li+ and O2, respectively. Therefore, we define surface electronegativity VSE (VSE = (VSEA + VSIP)/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.