Title: Topological nodal line states and a potential catalyst of hydrogen evolution in the TiSi family,
Abstract: Topological nodal line (DNL) semimetals, formed by a closed loop of the
inverted bands in the bulk, result in the nearly flat drumhead-like surface
states with a high electronic density near the Fermi level. The high catalytic
active sites associated with the high electronic densities, the good carrier
mobility, and the proper thermodynamic stabilities with $\Delta
G_{H^*}$$\approx$0 are currently the prerequisites to seek the alternative
candidates to precious platinum for catalyzing electrochemical hydrogen (HER)
production from water. Within this context, it is natural to consider whether
or not the DNLs are a good candidate for the HER because its non-trivial
surface states provide a robust platform to activate possibly chemical
reactions. Here, through first-principles calculations we reported on a new DNL
TiSi-type family with a closed Dirac nodal line consisting of the linear band
crossings in the $k_y$ = 0 plane. The hydrogen adsorption on the (010) and
(110) surfaces yields the $\Delta G_{H^*}$ to be almost zero. The topological
charge carries have been revealed to participate in this HER. The results are
highlighting that TiSi not only is a promising catalyst for the HER but also
paves a new routine to design topological quantum catalyst utilizing the
topological DNL-induced surface bands as active sites, rather than edge sites-,
vacancy-, dopant-, strain-, or heterostructure-created active sites.