Bilayer borophene: an efficient catalyst for hydrogen evolution reaction

The electrocatalytic hydrogen evolution reaction is a crucial technique for green hydrogen production. However, finding affordable, stable, and efficient catalyst materials to replace noble metal catalysts remains a significant challenge. Recent experimental breakthroughs in the synthesis of two-dimensional bilayer borophene provide a theoretical framework for exploring their physical and chemical properties. In this study, we systematically considered nine types of bilayer borophenes as potential electrocatalysts for the hydrogen evolution reaction. Our first-principles calculations revealed that bilayer borophenes exhibit high stability and excellent conductivity, possessing a relatively large specific surface area with abundant active sites. Both surface boron atoms and the bridge sites between two boron atoms can serve as active sites, displaying high activity for the hydrogen evolution reaction. Notably, the Gibbs free energy change associated with adsorption for these bilayer borophenes can reach as low as −0.002 eV, and the Tafel reaction energy barriers are lower (0.70 eV) than those on Pt. Moreover, the hydrogen evolution reaction activity of these two-dimensional bilayer borophenes can be described by engineering their work function. Additionally, we considered the effect of pH on hydrogen evolution reaction activity, with significant activity observed in an acidic environment. These theoretical results reveal the excellent catalytic performance of two-dimensional bilayer borophenes and provide crucial guidance for the experimental exploration of multilayer boron for various energy applications.