fig5

Figure 5. (A) DFT calculated free energy diagrams for HER on the 11 promising topological quantum materials with their corresponding surface termination. These eleven candidates are identified based on their optimal hydrogen adsorption energies, as discussed in Section 3.3. Some curves overlap due to similar ΔG_H* values among different materials and surface terminations; (B) Summary table listing the corresponding adsorption surfaces and their calculated ΔG_H* values. A ΔG_H* value close to 0 eV is regarded as optimal for effective HER catalytic activity. HER: Hydrogen evolution reaction; DFT: density functional theory; ΔG_H*: Gibbs free energy of hydrogen adsorption.