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Title: Significant Quantum Effects in Hydrogen Activation

Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H 2 up to ~190 K and for D 2 up to ~140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H 2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D 2 dissociation process is controlled by kinetics. Thesemore » data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Here, examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation.« less
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [3] ;  [4] ;  [4] ;  [3] ;  [2] ;  [4]
  1. Tufts Univ., Medford, MA (United States); Univ. of Hull, Hull (United Kingdom)
  2. Univ. College London, London (United Kingdom)
  3. Univ. of Wisconsin-Madison, Madison, WI (United States)
  4. Tufts Univ., Medford, MA (United States)
Publication Date:
Grant/Contract Number:
FG02-05ER15731
Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 8; Journal Issue: 5; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Research Org:
Univ. of Wisconsin-Madison, Madison, WI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Contributing Orgs:
EMSL at Pacific Northwest National Laboratory (PNNL); the Center for Nanoscale Materials at Argonne National Laboratory (ANL); and the National Energy Research Scientific Computing Center (NERSC); and the UK’s national high performance computing service HECToR
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; activation; hydrogen; kinetic Monte Carlo simulation; path integral density functional theory; quantum tunneling; single-atom alloy
OSTI Identifier:
1397234

Kyriakou, Georgios, Davidson, Erlend R. M., Peng, Guowen, Roling, Luke T., Singh, Suyash, Boucher, Matthew B., Marcinkowski, Matthew D., Mavrikakis, Manos, Michaelides, Angelos, and Sykes, E. Charles H.. Significant Quantum Effects in Hydrogen Activation. United States: N. p., Web. doi:10.1021/nn500703k.
Kyriakou, Georgios, Davidson, Erlend R. M., Peng, Guowen, Roling, Luke T., Singh, Suyash, Boucher, Matthew B., Marcinkowski, Matthew D., Mavrikakis, Manos, Michaelides, Angelos, & Sykes, E. Charles H.. Significant Quantum Effects in Hydrogen Activation. United States. doi:10.1021/nn500703k.
Kyriakou, Georgios, Davidson, Erlend R. M., Peng, Guowen, Roling, Luke T., Singh, Suyash, Boucher, Matthew B., Marcinkowski, Matthew D., Mavrikakis, Manos, Michaelides, Angelos, and Sykes, E. Charles H.. 2014. "Significant Quantum Effects in Hydrogen Activation". United States. doi:10.1021/nn500703k. https://www.osti.gov/servlets/purl/1397234.
@article{osti_1397234,
title = {Significant Quantum Effects in Hydrogen Activation},
author = {Kyriakou, Georgios and Davidson, Erlend R. M. and Peng, Guowen and Roling, Luke T. and Singh, Suyash and Boucher, Matthew B. and Marcinkowski, Matthew D. and Mavrikakis, Manos and Michaelides, Angelos and Sykes, E. Charles H.},
abstractNote = {Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H2 up to ~190 K and for D2 up to ~140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D2 dissociation process is controlled by kinetics. These data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Here, examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation.},
doi = {10.1021/nn500703k},
journal = {ACS Nano},
number = 5,
volume = 8,
place = {United States},
year = {2014},
month = {3}
}