The project at the University of California at Berkeley, under the supervision of Professor Enrique Iglesia, begins on June 1, 2020. During the first month of work, the researcher takes the necessary courses for safety in the laboratory. Likewise, he attends courses on the characterization of catalytic samples, so all characterization is carried out by the researcher himself, which is the reason for the acquisition of knowledge in the handling of X-ray Diffraction (XRD) or X-ray Photoelectron Spectroscopy (XPS) equipment. The researcher assembles his own reaction equipment in a fully equipped hood and in which the gas lines are available to carry out desired catalytic tests. The equipment itself has a chromatographic gas analyzer, which requires training for product analysis.
Different Cu and Pt catalysts were prepared by the researcher, supported either on Al2O3, SiO2, CeO2 or TiO2. Water-gas shift (WGS) reactions of all the prepared samples were performed on the built unit and measured rates were benchmarked against literature. This catalyst were intimately mixed with several diluents and several WGS reactions were performed, always observing a rate increase per surface metal atom, in cases where atomic contact between phases do not exist. This lack of contact in the intimate mixtures has been demonstrated by specific CO+H2 reactions where typical inhibitions of TiO2 supported materials were not detected. Therefore, the only possibility in here, as initially theorized, is the scavenging of a formed intermediate, and its derivation to CO2 and H2. The effect of temperature and different reactants cofeeding was also studied. During the first year of the project, 4 workshops regarding WGS promotion effects were given in the LSAC group.
For HCOOH decomposition project, Cu/SiO2 and Pt/SiO2 catalysts were prepared and tested. Different isotopologues (DCOOD, HCOOD and DCOOH) were also run in the unit in order to determine possible kinetic isotopic effects, determining for both catalysts the decomposition of the C-H bond as kinetically relevant step. These results were supported by the Density Functional Theory (DFT) calculations made using VASP software. Infrared experiments, combined with previously explained isotopic experiments, allowed us to determine that HCOOH decomposition followed different routes on Cu and Pt. While on the former, the H2 formation was produced with a bimolecular route in a HCOOH crowded surface, in the latter the surface is covered by strongly adsorbed CO with no detectable formate-derived species, leading to lower spaces on the metal surface for performing the catalysis. For both catalysts, accurate and experimentally reproducible rate expressions were written. During the last 6 months of the project, 2 workshops regarding HCOOH decomposition on metals were given in the LSAC group.
At the end of the project one manuscript has already been published (
https://doi.org/10.1016/j.jcat.2021.08.049(s’ouvre dans une nouvelle fenêtre)) regarding the study of HCOOH decomposition on Cu nanoparticles, where it was shown how crowded surfaces can facilitate catalysis by selectively stabilizing the relevant transition state more so than the precursor through interactions with more weakly bound species. This manuscript is openly accessible from virtual LSAC group library (
http://iglesia.cchem.berkeley.edu/Publications.html(s’ouvre dans une nouvelle fenêtre)). An additional manuscript is about to be submitted regarding HCOOH decomposition on Pt, although results still remain confidential. Preliminary results of this manuscript were disseminated during SECAT2021 congress, held in Valencia during 18-20 October 2021. Finally, at this moment, a last manuscript related to enhancement effects observed on WGS reaction is being written and it is expected to be published by mid-2022.
