Abstract
The atomic and electronic structure, thermodynamic stability, and effect of doping the O-terminated Ti(3)C(2) MXene (Ti(3)C(2)O(2)) by Hf, Nb, Ta, and Zr on the electrocatalytic activity for the hydrogen evolution reaction (HER) is investigated by means of periodic density functional theory (DFT)-based simulations. The preference of doping Ti(3)C(2)O(2) with the doping agent either in the outer or inner atomic layers is determined by formation energies' estimates. Among these studied systems, the case where one Hf substitutes one Ti atom in the Ti(3)C(2)O(2) inner layer appears to exhibit the optimum HER activity with a ΔG value of -0.27 eV only, lower than the corresponding value of -0.40 eV previously reported for stoichiometric Ti(3)C(2)O(2), implying an improved HER activity. Thus, doping MXenes with similar metal atoms appears to be an attractive approach to engineer the HER activity of this family of materials.