Efficient hydrogen evolution reaction due to topological polarization

One important application of topological materials is toward surface catalysis, particularly hydrogen evolution reaction (HER), which is an iconic procedure in the field of renewable energy. Based on systematic first-principles calculations for A₃B (A = Ni, Pd, Pt; B = Si, Ge, Sn), we propose that topological electric polarization characterized by the Zak phase can be crucial to designing efficient catalysts for the HER. For A₃B, we, for the first time in semimetals, show that the Zak phase takes a nontrivial value of π in the whole (111) projected Brillouin zone (PBZ), which causes quantized electric polarization charge accumulation at the surface. While the Zak phase covers the whole PBZ, we believe that the impact of topological properties is more significant than well-studied Weyl semimetals.

As a result, depending on the adsorption sites, the hydrogen (H) atom hybridizes with the topological surface states rather than with the bulk states, and the H states are localized in the energy spectrum. The Gibbs free energy difference (ΔG) due to the H adsorption becomes small, which is a highly favorable situation for the HER. Notably, we show that ΔG for Pt₃Sn and Pd₃Sn are just -0.066 and -0.092 eV, respectively, which are almost half of the value of well-known Pt. Our work proposes new candidates for Zak phase-related topological materials and bridges the connection between topology and surface sciences by showing the impact of topological polarization on HER.