Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh

Nirala Singh; Mal Soon Lee; Sneha A. Akhade; Guanhua Cheng; Donald M. Camaioni; Oliver Y. Gutiérrez; Vassiliki Alexandra Glezakou; Roger Rousseau; Johannes A. Lercher; Charles T. Campbell

doi:10.1021/acscatal.8b04039

Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh

Nirala Singh, Mal Soon Lee, Sneha A. Akhade, Guanhua Cheng, Donald M. Camaioni, Oliver Y. Gutiérrez, Vassiliki Alexandra Glezakou, Roger Rousseau, Johannes A. Lercher, Charles T. Campbell

Research output: Contribution to journal › Article › peer-review

62 Scopus citations

Abstract

In aqueous phase, the rates of hydrogenation of aromatic substrates such as phenol on Pt/C and Rh/C are influenced by varying activity of hydronium ions. Decreasing the pH from 8 to 1 increases the rate of hydrogenation of phenol on Pt at 20 bar H ₂ and 80 °C by 15-fold. This increase is attributed to weakening of the hydrogen binding energy (HBE) on the metal surface with decreasing pH. A weaker HBE at lower pH is also predicted by ab initio molecular dynamics simulations, providing atomistic insight into the impact of electrolyte ion distribution and interfacial solvent reorganization on HBE. The lower HBE results in a decrease in the activation energy for addition of adsorbed H from the metal to the adsorbed organic (with a Brønsted-Evans-Polanyi slope of ∼1). The kinetic model derived accounts also for the lack of pH dependence at low hydrogen coverages (at 1 bar H ₂ on Pt or up to 70 bar H ₂ on Rh), when the weakening of the HBE decreases the hydrogen coverage.

Original language	English
Pages (from-to)	1120-1128
Number of pages	9
Journal	ACS Catalysis
Volume	9
Issue number	2
DOIs	https://doi.org/10.1021/acscatal.8b04039
State	Published - Feb 1 2019
Externally published	Yes

Funding

The research described in this paper is part of the Chemical Transformation Initiative at Pacific Northwest National Laboratory (PNNL), conducted under the Laboratory Directed Research and Development Program at PNNL, a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy. N.S. acknowledges the Washington Research Foundation Innovation Fellowship. C.T.C. acknowledges the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences Division Grant No. DE-FG02-96ER14630 for support of this work.

Funders	Funder number
Office of Basic Energy Sciences
U.S. Department of Energy
Washington Research Foundation
Office of Science

Keywords

Brønsted-Evans-Polanyi
aqueous phase
hydrogen adsorption
hydrogenation
molecular dynamics simulations
pH effects
phenol
platinum

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10.1021/acscatal.8b04039

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title = "Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh",

abstract = " In aqueous phase, the rates of hydrogenation of aromatic substrates such as phenol on Pt/C and Rh/C are influenced by varying activity of hydronium ions. Decreasing the pH from 8 to 1 increases the rate of hydrogenation of phenol on Pt at 20 bar H 2 and 80 °C by 15-fold. This increase is attributed to weakening of the hydrogen binding energy (HBE) on the metal surface with decreasing pH. A weaker HBE at lower pH is also predicted by ab initio molecular dynamics simulations, providing atomistic insight into the impact of electrolyte ion distribution and interfacial solvent reorganization on HBE. The lower HBE results in a decrease in the activation energy for addition of adsorbed H from the metal to the adsorbed organic (with a Br{\o}nsted-Evans-Polanyi slope of ∼1). The kinetic model derived accounts also for the lack of pH dependence at low hydrogen coverages (at 1 bar H 2 on Pt or up to 70 bar H 2 on Rh), when the weakening of the HBE decreases the hydrogen coverage.",

keywords = "Br{\o}nsted-Evans-Polanyi, aqueous phase, hydrogen adsorption, hydrogenation, molecular dynamics simulations, pH effects, phenol, platinum",

author = "Nirala Singh and Lee, {Mal Soon} and Akhade, {Sneha A.} and Guanhua Cheng and Camaioni, {Donald M.} and Guti{\'e}rrez, {Oliver Y.} and Glezakou, {Vassiliki Alexandra} and Roger Rousseau and Lercher, {Johannes A.} and Campbell, {Charles T.}",

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doi = "10.1021/acscatal.8b04039",

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AU - Singh, Nirala

AU - Lee, Mal Soon

AU - Akhade, Sneha A.

AU - Cheng, Guanhua

AU - Camaioni, Donald M.

AU - Gutiérrez, Oliver Y.

AU - Glezakou, Vassiliki Alexandra

AU - Rousseau, Roger

AU - Lercher, Johannes A.

AU - Campbell, Charles T.

PY - 2019/2/1

Y1 - 2019/2/1

N2 - In aqueous phase, the rates of hydrogenation of aromatic substrates such as phenol on Pt/C and Rh/C are influenced by varying activity of hydronium ions. Decreasing the pH from 8 to 1 increases the rate of hydrogenation of phenol on Pt at 20 bar H 2 and 80 °C by 15-fold. This increase is attributed to weakening of the hydrogen binding energy (HBE) on the metal surface with decreasing pH. A weaker HBE at lower pH is also predicted by ab initio molecular dynamics simulations, providing atomistic insight into the impact of electrolyte ion distribution and interfacial solvent reorganization on HBE. The lower HBE results in a decrease in the activation energy for addition of adsorbed H from the metal to the adsorbed organic (with a Brønsted-Evans-Polanyi slope of ∼1). The kinetic model derived accounts also for the lack of pH dependence at low hydrogen coverages (at 1 bar H 2 on Pt or up to 70 bar H 2 on Rh), when the weakening of the HBE decreases the hydrogen coverage.

AB - In aqueous phase, the rates of hydrogenation of aromatic substrates such as phenol on Pt/C and Rh/C are influenced by varying activity of hydronium ions. Decreasing the pH from 8 to 1 increases the rate of hydrogenation of phenol on Pt at 20 bar H 2 and 80 °C by 15-fold. This increase is attributed to weakening of the hydrogen binding energy (HBE) on the metal surface with decreasing pH. A weaker HBE at lower pH is also predicted by ab initio molecular dynamics simulations, providing atomistic insight into the impact of electrolyte ion distribution and interfacial solvent reorganization on HBE. The lower HBE results in a decrease in the activation energy for addition of adsorbed H from the metal to the adsorbed organic (with a Brønsted-Evans-Polanyi slope of ∼1). The kinetic model derived accounts also for the lack of pH dependence at low hydrogen coverages (at 1 bar H 2 on Pt or up to 70 bar H 2 on Rh), when the weakening of the HBE decreases the hydrogen coverage.

KW - Brønsted-Evans-Polanyi

KW - aqueous phase

KW - hydrogen adsorption

KW - hydrogenation

KW - molecular dynamics simulations

KW - pH effects

KW - phenol

KW - platinum

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Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh

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