 The abstract states that there are different types of reaction mechanisms for oxygen evolution reaction, OER, which depend on the applied potential. These potential dependent mechanisms can be identified by combining grand canonical methods and microkinetic modelling. This allows us to understand how the applied potential affects the reaction kinetics and the resulting over potential, Tafel slope, and experimental observations. This article was authored by Ziyu Wang, William A. Goddard, and Hai Xiao.