Fig. 21.

a Top view of the stable structure of the monolayer Zr₂B₂. The brown and green balls represent the Zr and B atoms, respectively. b The energy during the diffusion process on the monolayer Zr₂B₂. Reproduced with permission from Ref. [230]. c Top view of 2D Y₂B₂ crystal structures. The Y and B atoms are denoted by brown and green spheres. d The diffusion energy barrier curves of M on Y₂B₂. Reproduced with permission from Ref. [234]. e The adsorption site of Li/Na on TiB₃ monolayer. f Diffusion barrier of Li and Na on TiB₃ monolayer along P1 and P2, respectively. Reproduced with permission from Ref. [231]