Formic acid decomposition on Au catalysts: DFT, microkinetic modeling, and reaction kinetics experiments

Abstract

A combined theoretical and experimental approach is presented that uses a comprehensive mean‐field microkinetic model, reaction kinetics experiments, and scanning transmission electron microscopy imaging to unravel the reaction mechanism and provide insights into the nature of active sites for formic acid (HCOOH) decomposition on Au/SiC catalysts. All input parameters for the microkinetic model are derived from periodic, self‐consistent, generalized gradient approximation (GGA‐PW91) density functional theory calculations on the Au(111), Au(100), and Au(211) surfaces and are subsequently adjusted to describe the experimental HCOOH decomposition rate and selectivity data. It is shown that the HCOOH decomposition follows the formate (HCOO) mediated path, with 100% selectivity toward the dehydrogenation products (CO2 + H2) under all reaction conditions. An analysis of the kinetic parameters suggests that an Au surface in which the coordination number of surface Au atoms is ≤4 may provide a better model for the active site of HCOOH decomposition on these specific supported Au catalysts. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1303–1319, 2014

Reexamination of CO formation during formic acid decomposition on the Pt(1 1 1) surface in the gas phase

“…The newly formed COOH in structure 3 binds to the surface in a zigzag configuration, as shown in Fig. 1, which is also reported by several research groups [8,21,22]. Such structure is identified as the common precursor for the subsequent formation of both CO 2 and CO.…”

Hydrogen Production from Formic Acid Attained by Bimetallic Heterogeneous PdAg Catalytic Systems

“…The supremacy of PdAg-catalysts over other compositions of the active metal phase has widely been demonstrated from experimental investigations but also by theoretical studies. As for many other reactions [99][100][101][102], density functional theory (DFT) calculations have been used to study the decomposition of FA. Huang et al reported a DFT study for the decomposition of FA over noble metals (Pt, Au, Pd, etc.)…”

Active sites and mechanisms for H 2 O 2 decomposition over Pd catalysts

“…We subsequently used sensitivity analysis to identify the sensitive DFT-derived BEs of surface species and transition-state energies. We then fit modelpredicted reaction rates to experimental rates (such that the residual error is less than 20%) by modifying sensitive parameters, constraining the adjustment of parameters such that (i) the deviation between DFT-derived BEs and activation barriers on a given Pd facet and the corresponding values from the microkinetic model should be within the ∼0.1-to 0.2-eV error bars generally attributed to DFT calculations (67), and (ii) the adsorbate coverage used in the DFT calculations should be consistent with the coverage predicted by the microkinetic model (that is, the solution should be self-consistent with respect to coverage). Next, we present the results from two model solutions that satisfy the above criteria, but differ in both the coverage and identity of the most abundant surface intermediate, and are denoted as the "O*-coverage solution" and the "OH*-coverage solution."…”