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

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 + H-2) 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. (c) 2014 American Institute of Chemical Engineers AIChE J, 60: 1303-1319, 2014