Hydrated (undecomposed) form of heteropolyacid H3PMo12O40/SiO2 exhibits a h
igher activity in the formic acid decomposition than the corresponding dehy
drated sample. The formic acid decomposition takes place on strong Bronsted
acid sites of the heteropolyacid. Ab initio SCF MO LCAO method was used fo
r 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 s
elective 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.