TY - JOUR
T1 - Influence of the Molecular Structure on the Electrocatalytic Hydrogenation of Carbonyl Groups and H2Evolution on Pd
AU - Meyer, Laura C.
AU - Sanyal, Udishnu
AU - Stoerzinger, Kelsey A.
AU - Koh, Katherine
AU - Fulton, John L.
AU - Camaioni, Donald M.
AU - Gutiérrez, Oliver Y.
AU - Lercher, Johannes A.
N1 - Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/10/7
Y1 - 2022/10/7
N2 - We investigated the electrocatalytic hydrogenation (ECH) of model aldehydes and ketones over carbon-supported Pd in the aqueous phase. We propose reaction mechanisms based on kinetic measurements and on spectroscopic and electrochemical characterization of the working catalyst. The reaction rates of ECH and of the H2evolution reaction (HER) vary with the applied electric potential following trends that strongly depend on the organic substrate. The intrinsic rates of hydrogenation and H2evolution are influenced, in opposing ways, by the sorption of the reacting organic substrate. Strong interactions, that is, higher standard free energies of adsorption of the organic compound, induce high hydrogenation rates. The fast hydrogenation kinetics produces a hydrogen-depleted environment that kinetically hinders the HER and the bulk phase transition of Pd to a H-rich bulk Pd hydride, which is triggered by the applied potential in the absence of reacting organic compounds. As a consequence of strong organic-metal interactions, hydrogenation dominates at low overpotential. However, the coverages of organic substrates on the metal surface decrease, and the rates of H2evolution surpass those of hydrogenation with increasingly negative electric potential. We determined the range of electric potential favoring hydrogenation on Pd and quantitatively deconvoluted the effects of the sorption of the organic compound, and of the rates of proton-coupled electron transfers, on the kinetics of both ECH and HER. The results indicate that electrocatalysis offers hydrogenation pathways for polar molecules which are different and, in some cases, faster than those dominating in the absence of an external electric potential.
AB - We investigated the electrocatalytic hydrogenation (ECH) of model aldehydes and ketones over carbon-supported Pd in the aqueous phase. We propose reaction mechanisms based on kinetic measurements and on spectroscopic and electrochemical characterization of the working catalyst. The reaction rates of ECH and of the H2evolution reaction (HER) vary with the applied electric potential following trends that strongly depend on the organic substrate. The intrinsic rates of hydrogenation and H2evolution are influenced, in opposing ways, by the sorption of the reacting organic substrate. Strong interactions, that is, higher standard free energies of adsorption of the organic compound, induce high hydrogenation rates. The fast hydrogenation kinetics produces a hydrogen-depleted environment that kinetically hinders the HER and the bulk phase transition of Pd to a H-rich bulk Pd hydride, which is triggered by the applied potential in the absence of reacting organic compounds. As a consequence of strong organic-metal interactions, hydrogenation dominates at low overpotential. However, the coverages of organic substrates on the metal surface decrease, and the rates of H2evolution surpass those of hydrogenation with increasingly negative electric potential. We determined the range of electric potential favoring hydrogenation on Pd and quantitatively deconvoluted the effects of the sorption of the organic compound, and of the rates of proton-coupled electron transfers, on the kinetics of both ECH and HER. The results indicate that electrocatalysis offers hydrogenation pathways for polar molecules which are different and, in some cases, faster than those dominating in the absence of an external electric potential.
KW - aqueous phase hydrogenation
KW - carbonyl compounds
KW - electrocatalysis
KW - palladium hydride
KW - proton-coupled electron transfer
UR - http://www.scopus.com/inward/record.url?scp=85138789085&partnerID=8YFLogxK
U2 - 10.1021/acscatal.2c03207
DO - 10.1021/acscatal.2c03207
M3 - Article
AN - SCOPUS:85138789085
SN - 2155-5435
VL - 12
SP - 11910
EP - 11917
JO - ACS Catalysis
JF - ACS Catalysis
IS - 19
ER -