Different shapes of 𝐶 total are resulted from the combination of 𝐶 H ad and 𝐶 OH ad that possess distributed equilibrium potentials, as shown in Figure , and vary among different measurements. The OH adsorption has a bimodal normal distribution and the one at lower potentials with p 1 < 5% is responsible for the terrace of 𝐶 total in the potential range of 0.55 -0.6 VRHE. The coverages of adsorbed H and OH are shown in Figure (g)-(i). Both 𝜃 H and 𝜃 OH are less than 5% in the double-layer region.