The measurement of infrared chemiluminescence of the nascent CO₂ molecules desorbed in molecular-beam surface reactions has been made to study the dynamics of HCOOH decomposition and HCOOH oxidation on metal surfaces (Pt, Ni). The formation of CO₂ in CO oxidation is a bimolecular process (i.e., the LH type reaction between CO(ad) and O(ad)), and vibrationally and rotationally excited CO₂ molecules are desorbed from the metal surfaces. In contrast, the CO₂ molecules produced by HCOOH decomposition on Pt(or Ni) are not so much excited as those by CO oxidation. The CO₂ is formed via decomposition of HC00(ad) (a unimolecular process) with the internal energy distributions as being in equilibrium with the surface temperature. The CO₂ formed by HCOOH oxidation (HCOOH+O₂ reaction) on the Ni surface is not excited, indicating that the dynamics of the CO₂ formation is similar to that of the HCOOH decomposition. On the Pt surface, however, the CO₂ is excited substantially, that is, the vibrational and rotational states of the CO₂ formed by the HCOOH+O₂ reaction are quite similar to those of the CO₂ formed by CO oxidation. This finding suggests that the final step of the CO₂ formation in the HCOOH oxidation on Pt comprises the bimolecular reaction between CO(ad) and O(ad). The difference in the internal energy distributions of the nascent CO₂ can provide us with new information on the dynamics of catalytic reactions.