Identifying of Pure and Defected Ti₂ C Materials Using Gas Probe Molecules: First Principles Calculations

Employing first principles calculations, we systematically investigated the geometrical and electronic structures of pure, titanium defected (D_Ti ) and carbon defected (D_C ) Ti₂ C materials. We found the defected Ti₂ C exhibits stronger metallic property than pure Ti₂ C due to the enhanced density of Ti-d orbital state near the Fermi level. We then studied the adsorption as well as the infrared spectrum (IR) response of the four kinds of gas molecules (CH₄ , NH₃ , CO and NO) on pure, D_Ti and D_C Ti₂ C surfaces. Simulations show that CO and NO molecules are chemically adsorbed on all Ti₂ C surface with similar adsorption sites. However, CH₄ and NH₃ molecules would be dissociated on Ti₂ C surface. Negative values of crystal orbital Hamilton population as well as the PDOS calculations show that the red shift in IR spectra of CO and NO molecules originates from the decreasing bonding strength of probe molecules. The present work provides rich insight for the adsorption and identification for different Ti₂ C materials.