All Boron Atoms in a ScB₁₂ Monolayer Contribute to the Hydrogen Evolution Reaction

The search for highly stable hydrogen evolution reaction (HER) catalysts with high activity, multiple active sites, and excellent electrical conductivity is crucial to promote the development of hydrogen energy. Here, we identify an entirely planar ScB₁₂ monolayer with desirable properties as an HER catalyst using an unbiased structure search combined with first-principles calculations. The superior stability and outstanding electrical conductivity of the ScB₁₂ monolayer are confirmed in detail. Most importantly, the HER catalytic activity of the ScB₁₂ monolayer is close to desirable (0.00 eV) according to the Gibbs free energy of hydrogen adsorption (ΔGH). Moreover, the earlier-adsorbed H atoms on the ScB₁₂ monolayer can effectively boost the catalytic activity of the following catalytic sites. Therefore, all atoms of the ScB₁₂ monolayer can contribute to HER. The theoretical ΔGH values at hydrogen coverage from 1/36 to 36/36 via the 2 × 2 ScB₁₂ supercell are in the range of −0.09 and 0.28 eV, which can be further adjusted to −0.18 and 0.00 eV under −1% biaxial strain. Furthermore, other new two-dimensional materials, which can be constructed with proper metals and the B₁₂ unit by diversified topologies, are inspired to further provide extendable possibilities of metal borides monolayers for materials and chemical applications.