Issue 19, 2020

Structural trends in the dehydrogenation selectivity of palladium alloys

Abstract

Alloying is well-known to improve the dehydrogenation selectivity of pure metals, but there remains considerable debate about the structural and electronic features of alloy surfaces that give rise to this behavior. To provide molecular-level insights into these effects, a series of Pd intermetallic alloy catalysts with Zn, Ga, In, Fe and Mn promoter elements was synthesized, and the structures were determined using in situ X-ray absorption spectroscopy (XAS) and synchrotron X-ray diffraction (XRD). The alloys all showed propane dehydrogenation turnover rates 5–8 times higher than monometallic Pd and selectivity to propylene of over 90%. Moreover, among the synthesized alloys, Pd3M alloy structures were less olefin selective than PdM alloys which were, in turn, almost 100% selective to propylene. This selectivity improvement was interpreted by changes in the DFT-calculated binding energies and activation energies for C–C and C–H bond activation, which are ultimately influenced by perturbation of the most stable adsorption site and changes to the d-band density of states. Furthermore, transition state analysis showed that the C–C bond breaking reactions require 4-fold ensemble sites, which are suggested to be required for non-selective, alkane hydrogenolysis reactions. These sites, which are not present on alloys with PdM structures, could be formed in the Pd3M alloy through substitution of one M atom with Pd, and this effect is suggested to be partially responsible for their slightly lower selectivity.

Graphical abstract: Structural trends in the dehydrogenation selectivity of palladium alloys

Supplementary files

Article information

Article type
Edge Article
Submitted
14 2月 2020
Accepted
26 4月 2020
First published
05 5月 2020
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2020,11, 5066-5081

Structural trends in the dehydrogenation selectivity of palladium alloys

S. C. Purdy, R. R. Seemakurthi, Garrett M. Mitchell, M. Davidson, B. A. Lauderback, S. Deshpande, Z. Wu, E. C. Wegener, J. Greeley and J. T. Miller, Chem. Sci., 2020, 11, 5066 DOI: 10.1039/D0SC00875C

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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