Effect of a Surface Area and a d‐Band Oxidation State on the Activity and Stability of RuOx Electrocatalysts for Oxygen Evolution Reaction

Abstract

It is widely recognized that RuO2 is the best electrocatalysts for oxygen evolution reaction (OER) in water splitting in acidic media. In this study, we investigated the effect of a surface area and a d‐band oxidation state on the activity and the stability of RuO x electrocatalysts for OER. We synthesized RuO x thin film on glassy carbon electrode by the radio frequency magnetic sputtering and controlled the deposition temperature to vary the surface morphology and the electronic structure. In particular, we obtained a precise d‐band valence structure by using the synchrotron beam. A higher surface area and a more stable Ru4+ state were obtained at a lower deposition temperature owing to a smaller grain size and a lower oxidation state, respectively. As a result, the order of activity and stability is clearly consistent with that of surface area and stable Ru4+ state (RuO x > RuO x 200 > RuO x 400 > RuO x 600). Hence, we suggest that the surface area and the Ru d‐band oxidation state should be carefully controlled in the synthesis process in order to enhance the activity and the stability of RuO x electrocatalysts for OER.