Catalytic Decomposition of Formic Acid on Ru(001): Transient Measurements.

The kinetics of decomposition of formic acid on Ru(001) have been investigated with thermal desorption mass spectrometry following the adsorption of DCOOH and HCOOH at both 130 and 305 K. Formic acid chemisorbs dissociatively on the perfect (001) surface via O–H bond cleavage to form a formate and a hydrogen adatom, and at defect (step) sites on the surface via C–O bond cleavage to form CO, a hydrogen adatom and a hydroxyl. The saturation fractional coverage of the dissociatively chemisorbed formic acid is approximately 0.33 following adsorption at 130 K, and approximately 0.49 following adsorption at 305 K. Thermal desorption spectra of CO2 are a direct probe of the kinetics of C–H bond cleavage of the formate and are characterized by a kinetic isotope effect (C–H vs C–D bond cleavage), a progressively narrowing peak width, and an upward shift in peak temperature with increasing surface coverage of the formate.The latter indicates an increasing apparent activation energy for the C–H bond cleavage reactio...