For the free energy calculation, the zero-point energy, entropy correction was from the ab-initio frequency from VASP(IBRION=5), which is the second order derivatives of the energy with different position of the ions using finite differences approach. The cutoff frequency is 12 cm -1 . For the surface adsorbates, we used Harmonic limit approximation to calculate the energy. For the molecules in gas phase, we used ideal gas approximation to calculate the energy. The temperature used in free energy calculation was set as experimental temperature (60℃ ,~333K). The computational hydrogen electrode (CHE) model was applied to calculate the electron transfer steps in the free energy diagram.