Mechanism of formic acid decomposition on P-Mo heteropolyacid

Hydrated (undecomposed) form of heteropolyacid H3PMo12O40/SiO2 exhibits a higher activity in the formic acid decomposition than the corresponding dehydrated sample. The formic acid decomposition takes place on strong Bronsted acid sites of the heteropolyacid. Ab initio SCF MO LCAO method was used for the calculation of the electronic state of two surface complexes of HCOOH molecule (S1 and S2) coordinated to a proton H+. The S1 complex is formed by proton addition to the carbonyl oxygen, whereas the S2 complex is formed by proton addition to the oxygen atom of the C-O-H fragment of HCOOH The selective weakening of the C-O bond and localization of the positive charge on the (O=C-H) fragment in the protonated complex S2 are favorable for the decomposition of formic acid to CO and H2O.