Fig. 6. The illustration depicts the HER process facilitated by TiB in three distinct forms: (a) the bulk form of TiB; (b) a TiB monolayer extracted from the bulk for investigating its electronic properties and reactivity; and (c) a TiB layer that has undergone surface functionalization to enhance its efficiency in the HER process. Reproduced with permission from ref. 80. Copyright 2019 American Chemical Society.