Band Gap as a Novel Descriptor for the Reactivity of 2D Titanium Dioxide and its Supported Pt Single Atom for Methane Activation.

Ultrathin transition-metal oxides (TMOs) from nonlayered bulk structures are emerging 2D materials. Here we investigate the reactivity of a 2D TMO of varying thickness from first principles. We find that the band gap of the 2D nL-TiO2(110) shows a strong linear correlation with its surface reactivity: the smaller the band gap, the more reactive the surface oxygen; 3L-TiO2(110) has the smallest band gap and the highest reactivity. We further design Pt1 single-atom catalysts (SAC) by substituting a Pt single atom for a surface Ti atom. We find that the band gap of nL-TiO2(110) dictates both chemisorption and dissociation of CH4 on Pt1-nL-TiO2(110): the smaller the band gap, the stronger the adsorption of CH4 and the lower the barrier of heterolytic C-H activation of CH4. We propose that band gap can be a novel and direct descriptor for the reactivity of 2D TMOs and their supported SACs.