Ethylene hydrogenation on supported Ni, Pd and Pt nanoparticles: Catalyst activity, deactivation and the d-band model

Ethylene hydrogenation catalyzed at 300 K by 1-1.5 nm nanoparticles of Ni, Pd and Pt supported on MgO (100) with a narrow size-distribution, as well as the deactivation under reaction conditions at 400 K, was investigated with pulsed molecular beam experiments. Ni nanoparticles deactivate readily at 300 K, whereas Pd particles deactivate only after pulsing at 400 K, and Pt particles were found to retain hydrogenation activity even after the 400 K heating step. The hydrogenation turnover frequency normalized to the number of particles exhibited the trend, Pt > Pd > Ni. The activity/deactivation was found to scale with the location of the particles' d-band centroid, epsilon(c), with respect to the Fermi energy of the respective metals calculated with density-functional theory. An epsilon(c) closer to the Fermi level is indicative of a facile deactivation/low activity and an epsilon(c) farther from the Fermi level is characteristic of higher activity/impeded deactivation. CO adsorption, probed with infrared reflection absorption spectroscopy was used to investigate the clusters before and after the reaction, and the spectral features correlated with the observed catalytic behavior. (C) 2015 Elsevier Inc. All rights reserved.