Mechanistic insights into the dehydrogenation of formaldehyde, formic acid and methanol using the Pt₄ cluster as a promising catalyst

Reaction mechanisms of the dehydrogenation of formaldehyde, formic acid and methanol on the Pt₄ cluster were computationally investigated using density functional theory (DFT) with the B3LYP functional in the conjunction with the aug-cc-pVTZ basis sets for H, C and O atoms, and the cc-pVDZ-PP basis set for Pt. Herein, the key mechanistic aspects of three possible pathways of the dehydrogenation of these compounds are summarized. The results indicate that the formation of H₂ and CO or CO₂ molecules is more energetically favorable than the generation of H and H₂O, HCHO products. Generally, the formation of H₂ molecule in the presence of catalysts is more favorable than the direct decomposition of either HCHO, HCOOH or CH₃OH molecule. The use of Pt₄ catalyst significantly reduces the energy barriers for C-H and O-H bond cleavage of all three compounds to 14, 9 and 12 kcal/mol, respectively. The decomposition of HCOOH is found to be the most energetically favorable. In addition, the mechanistic insights of the reactions confirm the reduction of the energy barriers of the gas-phase dehydrogenation by 67-82 kcal/mol and bring it to the values smaller than 14 kcal/mol in the presence of the Pt₄ catalysts.