Fig. 5
Energy diagram of different RuCxNy structures from first principles calculations. The x axis is reaction free energy of hydrogen binding, where the negative values indicate strong binding while positive values indicate weak binding. The dark blue range indicates the candidate active sites with the best activity. The y Axis is formation energy of each configuration, where a more positive value signifies a structure that is more difficult to form. The colors denote candidate active sites: H binds to a ruthenium atom along the perpendicular direction to the plane (black), a carbon atom next to the ruthenium (yellow), a carbon atom next to nitrogen (green), or a carbon atom far away from ruthenium and nitrogen atoms (purple). The note records the data point from a certain structure, number records the possible active site. The version with complete RuCxNy configurations can be found in Supplementary Figure 14 and the structures can be found in Supplementary Figure 15
