Fig. 3. (a) (i) Structure of Nb₂C–OF, (ii) structure of Ni adsorbed Nb₂C–OF, (iii) the side-view of Nb₂C–OF, (iv) the side-view of Ni adsorbed Nb₂C–OF, (b) total density of state (TDOS) for Nb₂C–OF and Ni adsorbed Nb₂C–OF, (c) (left) total density of states of Ni–(ad)Nb₂C–OF in unit cell and individual atoms in a cell + band structure (right), (d) experimental and theoretical optical properties of doped MXene.