Density functional study on formic acid decomposition on Pd(111) surface: a revisit and comparison with other density functional methods.

The mechanism of formic acid decomposition on the Pd(111) surface has been investigated by several theoretical methods in previous studies, including PBE and PW91. These results indicated that the mechanism is different from different methods, and even by using the same method (i.e., PBE), the mechanism is also different. In this study, we have revisited the formic acid decomposition on Pd(111) surface by using another density functional RPBE and by including van der Waals interaction which is neglected in the previous studies. Our results showed that the formic acid is decomposed via O-H bond cleavage to form bi-HCOO*, and the most favorable pathway is HCOOH* → bi-HCOO* + H* → CO2* + 2H*. The energy barrier is 0.55 eV at the rate-determining step. This conclusion is consistent with one of the PBE study. This demonstrated that computational methods have a great influence on the reaction mechanism, and care should be taken in selecting the appropriate computational methods.