PNNL

Abstract

Adsorbed hydrogen and phenol on Pt nanoparticles during (electro)catalytic hydrogenation are explored by combining X-ray absorption spectroscopy and ab initio simulations. Direct evidence for two types of Pt-C bonds at the surface of the metal particles detected by X-ray absorption spectroscopy suggest strong bonding between metal and the carbon support as well as adsorption of phenol nearly parallel to the surface. Hydrogen and phenol compete for accessible Pt sites. The surface concentrations are compatible with the proposal that atomic hydrogen and chemisorbed phenol are the species reacting in the rate-determining step of hydrogenation in the presence and absence of an external cathodic potential. During electrocatalytic hydrogenation the external electric potential controls the concentration of species on the surface, but does not impose structural or electronic property changes of the Pt compared to Pt particles in presence of hydrogen gas. Increasing reaction rates with increasing cathodic potential are attributed to the increase in chemical potential of adsorbed H. N.S. is funded by the WRF Innovation Fellowship in Clean Energy Institute. The research described in this paper is part of the Chemical Transformation Initiative at Pacific Northwest National Laboratory (PNNL), conducted under the Laboratory Directed Research and Development Program at PNNL, a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy. Computational resources used by M.-T.N., D.C., V.-A.G., and R.R., were provided by DOE’s National Energy Research Scientific Computing Center located at Lawrence Berkeley National Laboratory and PNNL institutional computing. N.G. acknowledges computational resources for the XANES calculations provided by the Environmental Molecular Sciences Laboratory (EMSL), which is a DOE Office of Science User Facility located at PNNL. This research used resources of the Advanced Photon Source Sector 20, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The authors would like to thank Kamlesh Suthar and Scott Russell for help in designing the cell.