Binding Energy and Diffusion Barrier of Formic Acid on Pd(111)

Jan Fingerhut; Loïc Lecroart; Dmitriy Borodin; Michael Schwarzer; Stefan Hörandl; Alexander Kandratsenka; Daniel J Auerbach; Alec M Wodtke; Theofanis N Kitsopoulos

doi:10.1021/acs.jpca.2c07414

Binding Energy and Diffusion Barrier of Formic Acid on Pd(111)

J Phys Chem A. 2023 Jan 12;127(1):142-152. doi: 10.1021/acs.jpca.2c07414. Epub 2022 Dec 30.

Authors

Jan Fingerhut¹, Loïc Lecroart², Dmitriy Borodin^{1

2}, Michael Schwarzer¹, Stefan Hörandl¹, Alexander Kandratsenka², Daniel J Auerbach², Alec M Wodtke^{1

2

3}, Theofanis N Kitsopoulos^{1

2

4

5}

Affiliations

¹ Institute for Physical Chemistry, Georg-August University of Goettingen, Goettingen 37077, Germany.
² Department of Dynamics at Surfaces, Max Planck Institute for Multidisciplinary Sciences, Goettingen 37077, Germany.
³ International Center for Advanced Studies of Energy Conversion, Georg-August University of Goettingen, Goettingen 37077, Germany.
⁴ Department of Chemistry, University of Crete, Heraklion 715 00, Greece.
⁵ Institute of Electronic Structure and Laser - FORTH, Heraklion 70013, Greece.

Abstract

Velocity-resolved kinetics is used to measure the thermal rate of formic acid desorption from Pd(111) between 228 and 273 K for four isotopologues: HCOOH, HCOOD, DCOOH, DCOOD. Upon molecular adsorption, formic acid undergoes decomposition to CO₂ and H₂ and thermal desorption. To disentangle the contributions of individual processes, we implement a mass-balance-based calibration procedure from which the branching ratio between desorption and decomposition for formic acid is determined. From experimentally derived elementary desorption rate constants, we obtain the binding energy 639 ± 8 meV and the diffusion barrier 370 ± 130 meV using the detailed balance rate model (DBRM). The DBRM explains the observed kinetic isotope effects.