Exploring the hydrogen evolution catalytic activity of the orthorhombic and hexagonal borophene as the hydrogen storage material

Although the hydrogen evolution reaction of the triangular borophene has been studied, the stability and hydrogen evolution reaction of the currently known borophene structure are unclear. To solve the key problem, the ab-initio calculation is used to study the structure and hydrogen evolution catalytic activity of the two novel borophene structures (orthorhombic:Pmmn and hexagonal: Pmmm), and the triangular-type borophene for comparison. The results show that the Pmmn borophene exhibits excellent hydrogen evolution reaction activity at a suitable hydrogen coverage, while the Gibbs free energy is only-0.003 eV. Essentially, the high activity of the Pmmn borophene can be attributed to two important factors. Compared to the triangular-type borophene structure, the adsorbed state enhances the electronic transport capacity of the Pmmn borophene structure. In particular, there is a unique charge distribution on the adsorption state of basal plane. Therefore, the interzonal distribution of the electronic consuming and accumulation region enhances the catalytic activity of the Pmmn borophene structure. This result is demonstrated by the exchange current versus in the volcano curve. Finally, it is found that the predicted structures (Pmmn and Pmmm) have strong ultraviolet response, which is able to reflect visible and infrared response.