Quantifying Adsorption of Organic Molecules on Platinum in Aqueous

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Quantifying Adsorption of Organic Molecules on Platinum in Aqueous Phase by Hydrogen Site Blocking and In Situ X-ray Absorption Spectroscopy Nirala Singh, Udishnu Sanyal, John L. Fulton, Oliver Y. Gutiérrez, Johannes A. Lercher, and Charles T. Campbell ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.9b01415 • Publication Date (Web): 07 Jun 2019 Downloaded from http://pubs.acs.org on June 7, 2019

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Quantifying Adsorption of Organic Molecules on Platinum in Aqueous Phase by Hydrogen Site Blocking and In Situ X-ray Absorption Spectroscopy Nirala Singh,1,2,3,4 Udishnu Sanyal,2 John L. Fulton,2 Oliver Y. Gutiérrez,2 Johannes A. Lercher,2, 5*

1

Charles T. Campbell1*

Department of Chemistry, University of Washington, Seattle, Washington 98105-1700, United

States 2

Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington

99354, United States 3

Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109,

United States 4

Catalysis Science and Technology Institute, University of Michigan, Ann Arbor, Michigan

48109, United States 5

Department of Chemistry and Catalysis Research Center, Technische Universität München,

Lichtenbergstrasse 4, 85748 Garching, Germany KEYWORDS. Adsorption energy, aqueous-phase hydrogenation, cyclic voltammetry, X-ray absorption spectroscopy, electrocatalysis, phenol, benzaldehyde

ACS Paragon Plus Environment

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ABSTRACT. The adsorption equilibrium constants of phenol, benzaldehyde, cyclohexanol, and benzyl alcohol on Pt in aqueous phase have been determined via cyclic voltammetry (CV) measuring the capacity to adsorb hydrogen in the presence of organic molecules. The enthalpies of adsorbed phenol on Pt in aqueous phase estimated by this technique were approximately –41 and –21 kJ/mol relative to aqueous phenol for sites on (110)/(100)-like sites and (111) facets, respectively. The enthalpy of phenol aqueous adsorption on (111) (–21 kJ/mol) can be compared to the gas phase enthalpy of adsorption of phenol on single crystal Pt(111) from previous work (–200 kJ/mol), to understand the individual factors influencing adsorption in liquid phase. The results show that adsorbates with very strong intrinsic bonding at a gas / solid interface have markedly reduced adsorption enthalpy due to strong solvation of both the Pt surface and the organic. Using the CV method, the decrease of the heat of adsorption in the sequence benzaldehyde > benzyl alcohol > phenol > cyclohexanol points to a strong interaction of the aromatic ring with the metal surface. Combining CV and X-ray absorption spectroscopy, we show that the inhibition of hydrogen adsorption by organic molecules is a suitable method of determining the coverage of organic reactants and that these molecules have defined Pt-C bonds in adsorbed state.

INTRODUCTION Adsorption equilibrium constants and adsorption energies are critical for understanding catalyzed reactions, yet these values are challenging to acquire for small hydrocarbons and oxygenates in aqueous solution.1 However, aqueous phase reactions such as electrochemical reduction or thermal hydrogenation reactions are important for sustainably and selectively transforming chemicals such as synthesizing fuels or remediating waste.2 This includes many reactions of great current interest with respect to biomass conversion, especially the electrocatalytic hydrogenation of bio-oil streams.3 Active and selective catalysts are required to enable these processes. Certain Pt group metals have been used for hydrogenation of model compounds approximating bio-oil,4,5 but more active and selective catalysts are required, as well as an improved understanding of their catalytic behavior. Here, we report indirect measurements of the adsorption equilibrium constants on Pt in aqueous phase for several oxygenates (phenol, benzaldehyde, cyclohexanol and benzyl alcohol), using cyclic voltammetry (CV), quantifying the fraction of sites they occupy by measuring the blocking of hydrogen adsorption. Estimating the fraction of hydrogen adsorbed in the presence of organic molecules by CV allows us to determine their equilibrium adsorption constants in aqueous phase. The adsorption equilibrium constants are determined by fitting measured coverages of the oxygenates as a function of their aqueous phase concentrations. Cyclic voltammetry is used to determine the fractional coverages of hydrogen and indirectly of the organic molecules. The current associated with hydrogen underpotential deposition (Hupd) is used to measure this fraction of H sites that is blocked. In this voltage range, we assume only H adsorbs/desorbs (i.e., OH* is not formed). The approach consists of the deposition of submonolayer amounts of hydrogen adatoms (Hupd) on the metal surface at less reducing potentials than required to reduce aqueous H+ to H2(gas), where the amount of charge (current times time) passed during electrochemical deposition or removal is proportional to the amount of hydrogen deposited on the metal or removed from its surface.6–8 The hydrogen chemical potential required to adsorb this monolayer is known based on the applied electrochemical potential, and depends on the crystal face of the metal.6,9 Removal


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occurs at nearly the same potential, indicating a reversible process for Hupd ⇌ H+(aq) + e–(Pt) + * (where * is a free site on Pt) at any given potential within the underpotential deposition region.6–8 During hydrogen underpotential deposition, the presence of organics inhibits the adsorption of hydrogen, as reported for phenol10 and other organics.11–13 The decrease in the charge corresponding to hydrogen adsorption/desorption peaks in CV is generally attributed to adsorbed organic molecules, which block sites that would otherwise adsorb hydrogen.10–12 As the orientation of phenol (adsorbed parallel to the surface) is constant at low coverages14 and the reduction in the current/charge of the hydrogen adsorption/desorption peaks in CV is caused by adsorbed phenol blocking sites, the coverage of phenol at different phenol solution concentrations has been extracted from the difference in charge with and without phenol. 10 The same concept has been applied already to other organic molecules on Pt11,12 and other metals15. We show here that such data can be fitted to a dual site Temkin adsorption model to derive coverage-dependent adsorption equilibrium constants. We extract from these the enthalpy of adsorption as a function of coverage, using estimates of the standard-state entropy of adsorption based on reported experimental trends.16 We also present X-ray absorption spectroscopy (XAS) measurements under aqueous conditions, which directly probe the surface coverages of the hydrogen by X-ray absorption near edge spectroscopy (XANES) and organic species by extended X-ray absorption fine structure (EXAFS based on Pt-C scattering), to corroborate conclusions derived from electrochemical measurements. EXPERIMENTAL METHODS Cyclic Voltammetry. A Pt wire (0.5 mm diameter, 99.99%) was first cleaned by a flame to remove adventitious organics then cleaned with Millipore water. For some measurements, a Pt disk (Pine) was used with consistent results compared to the Pt wire. The Pt disk was cleaned thoroughly with iso-propanol and Millipore water. A glass H-cell cleaned with iso-propanol to remove organics followed by drying then several series of further rinsing with Millipore water was used for the measurements. A Nafion membrane was used to separate the compartment containing the working electrode from the counter electrode. An Ag/AgCl reference electrode with double junction protection was used to minimize contamination, and the reference electrode was measured against a Pt wire in 1 bar H2 in the same electrolyte to calibrate to 0 V vs. reversible hydrogen electrode (RHE). After voltammetric cleaning of the Pt wire electrode or the Pt disk electrode, the cyclic voltammograms were measured with 10, 20, 50 mV/s scan rates to verify the absence of scan rate effects. We show 20 mV/s scan rates for the rest of the work unless explicitly mentioned otherwise. The electrolyte was 100 mM acetic acid (Sigma Aldrich, 99.995%) and 100 mM sodium acetate (99.999%) (pH 5). The organics were phenol (Sigma Aldrich, unstabilized >99%), benzaldehyde (Sigma Aldrich >99%), cyclohexanol (Sigma Aldrich 99%), cyclohexanone (Sigma 99.8%), and benzyl alcohol (Sigma Aldrich, 99.8%). The amount of underpotentially deposited hydrogen adatoms (Hupd) was calculated by measuring the charge (current x time integral) during deposition and desorption sweeps and subtracting the charge from the baseline capacitance current. The values plotted are the charge from H upd desorption (which generally were within experimental error, or ~10%, of the corresponding Hupd charge from adsorption). The effect of organic adsorption on Hupd was shown to be reversible for benzene on Pt.11,17 Although ideally the CV and in situ X-ray Absorption Spectroscopy measurements would be performed on identical catalysts, the CV isotherm technique would not be reliable on the 5 wt% Pt/C sample, since the


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Hupd peaks could not be distinguished from the double layer capacitance background current from the carbon support, which dominates at low metal loadings. One could possibly address this using a higher loading Pt/C (e.g., 30 wt% Pt/C), which has been shown to have quantifiable Hupd peaks that can be used to count available surface sites.18,19 However, the particle sizes would be larger than used here, and so of limited additional value for X-ray Adsorption Spectroscopy to detect surface changes. X-ray Absorption Spectroscopy. A custom built electrochemical cell was used for XANES and EXAFS.20 The as-purchased 5 wt% Pt/C catalyst (Sigma Aldrich) was calcined at 200 °C in air to remove adventitious carbon on the metal surface. Measurements of the Pt nanoparticle size from STEM and H2 chemisorption gave diameter of approximately 2.5 nm. The catalyst (Pt/C 2.5 nm) was deposited onto a carbon felt (Alfa Aesar) by syringe filtration. In 100 mM acetic acid and 100 mM sodium acetate the electrode was reduced, then run through a cleaning step consisting of 5 minutes at 1.3 V then 5 minutes at –0.8 V vs. Ag/AgCl. Following cleaning, the catalyst was exposed to new electrolyte with different concentrations of organics. The electrolyte was purged with argon and degassed before introduction to the electrochemical cell. Between each run, the Pt surface was cleaned by this same oxidative cycle followed by reductive cycle. This catalyst preparation and initial cleaning procedure was proven previously to lead to clean catalyst surfaces as evidenced by the catalytic activity for aqueous-phase catalytic hydrogenation of phenol,21,22 which gave rates per Pt surface atom that agreed with previous literature (using amount of adsorbed hydrogen to determine the amount of surface Pt). The Pt L3 edge spectra were taken at Sector 20 of the Advanced Photon Source in Argonne National Laboratory. Data analysis was done using Athena software and EXAFS fitting was done using Artemis.23 Fitting of the EXAFS data was done as discussed in detail in ref. 20. In brief, three Pt-Pt shells were used for fitting and the Pt foil spectra was taken simultaneously with the samples. RESULTS AND DISCUSSION Cyclic Voltammetry Results for Pt Wire and Disk. Figure 1 shows the Hupd adsorption/removal region of the CV for Pt in acetate buffer (pH 5) and with different concentrations of phenol, benzaldehyde, benzyl alcohol or cyclohexanol. The Hupd adsorption and removal is reversible, such that the process Hupd ⇌ H+(aq) + e–(Pt) + * is essentially at equilibrium at each potential within the underpotential deposition region.6–8 The results for Pt and phenol in Figure 1a agree well with those reported in sulfuric acid.10 Phenol oxidation occurs at a higher potential than applied here (1.57 V vs. RHE in pH 12 solution),24 and its reduction is observed at a lower potential ( phenol on Pt), and is supported by the higher Pt-C coordination. The adsorption energies determined on Pt for phenol, benzaldehyde, benzyl alcohol and cyclohexanol can help explain observed activity trends. Both phenol and benzaldehyde hydrogenation is low order at moderate concentrations, and the presence of cyclohexanol does not significantly inhibit phenol hydrogenation, due to its much weaker binding to Pt than phenol.


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APPENDIX. Derivation of gas-phase equilibrium constant and enthalpy from aqueous-phase equilibrium constant for adsorption The following derivation is for phenol (P) but is also essentially the same for all the organics. We assume the activity coefficients are equal to 1 at the concentrations used here. Phenol (P) adsorbs onto an empty site on Pt from aqueous solution: (A1) 𝑃(𝑎𝑞) + ∗ ⇌ 𝑃 ∗ Since H is also competitively adsorbing on the same type of sites during a CV, this can be written as: (A2) 𝐻 + (𝑎𝑞) + 𝑒 − (𝑃𝑡) + ∗ ⇌ 𝐻 ∗ 𝜃𝑃 is the coverage of P, 𝜃𝐻 is the coverage of H*, and 𝜃∗ is the remaining coverage of free sites. The equilibrium constant for P adsorbing on the surface is given by: 𝐾𝑃 =

𝜃𝑃 𝐶𝑃 𝜃∗

(A3)

Site balance requires that: 𝜃𝑃 + 𝜃𝐻 + 𝜃∗ = 1

(A4)

Using Equation (A4) to solve for 𝜃∗, and substituting it into Equation (A3) gives: 𝜃𝑃 𝐶𝑃 (1 − 𝜃𝑃 − 𝜃𝐻 )

(A5)

𝜃𝑃 𝐾𝑃 𝐶𝑃 = (1 − 𝜃𝐻 ) (1 + 𝐶𝑃 𝐾𝑃 )

(A6)

𝐾𝑃 = which can be rearranged to give:

Thus, at any constant value of 𝜽𝑯 , we can fit the relative coverage of A to the standard 1st-order Langmuir adsorption / desorption equation (i.e., the right side of Equation (A6)) to get KP, just as we have done in the main text. The resulting KP value found in this way is really KP(1-H), but since H is low in the way we actually apply this (see below), its value is only slightly changed by the competitive H adsorption. The lineshape of the CVs (for a given Pt site type) is almost the same independent of P(aq) concentration (at least on the right half of the CVs, which is the lower-H-coverage side). (As noted in the text, the overall CV lineshape changes with P(aq) concentration because the Pt(110)- and (100)-like sites are blocked at lower concentrations than the Pt(111)-like sites, but the line-shapes of each of the site-types is almost constant, and only attenuated in intensity with P(aq) addition.) Therefore, one can go to different voltages in the CVs to get the same 𝜃𝐻 (for that Pt site type) at different P(aq) concentrations. It is true that this line-shape stability may break down on the left-half of the CVs (where the H coverage gets high), so our method works best if only used for H coverages found on the right half of the CVs (i.e., low H coverages). This is just as one would expect intuitively, since this is where the H* least affects the adsorption of P*. Equation (1) in the main text is:


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𝜃/(1 − 𝜃) 𝑎𝑞 𝐶𝑜𝑟𝑔𝑎𝑛𝑖𝑐 = 𝐾𝑒𝑞,𝜃 . 0 0 𝜃 /(1 − 𝜃 ) 𝐶0

(1)

It is just a rearranged version of Equation (A6), where the constant factor (1 − 𝜃𝐻 ) has been dropped for the reasons outlined above, and the two concentration terms (Corganic and 𝜃/(1 − 𝜃)) have been normalized by their standard-state values to convert them to thermodynamic activities, so that the resulting KP value is rigorously connected to the standard-state reaction free energy,16 as in Equation (2). Equation (1) can be written in a slightly modified form as follows, whenever 𝜃 0 is chosen to be 0.5: 𝜃 𝐶𝑃 𝐶𝑃 𝑎𝑞 −𝛼𝜃/𝑅𝑇 𝑎𝑞 =( ) 𝐾 = ( )𝐾 𝑒 𝑒𝑞,𝜃 ⏟ (A7) 1−𝜃 𝐶0 𝐶0 ⏟𝑒𝑞,0 𝑎𝑞

𝑎𝑞

𝐾𝑒𝑞,𝜃 (𝑢𝑛𝑖𝑡𝑙𝑒𝑠𝑠)

𝐾𝑒𝑞,𝜃 (𝑢𝑛𝑖𝑡𝑙𝑒𝑠𝑠)

where 𝐶𝑃 is the concentration of phenol in the aqueous phase. To modify this to another 𝜃 0 value just 𝑎𝑞 requires multiplying 𝐾𝑒𝑞,𝜃 by 𝜃 0 /(1 − 𝜃 0 ). If phenol also is in equilibrium with the gas phase, the combined reactions can be written as: 𝑃(𝑔𝑎𝑠) ⇌ 𝑃(𝑎𝑞) ⇌ 𝑃(𝑎𝑑, 𝑎𝑞) The equilibrium partial pressure of P (𝑃𝑃 ) is given by: 𝑃𝑃 𝐶𝑃 ( 0 ) = 𝐾𝐻 𝑃 𝐶0

(A8)

where KH is Henry’s law constant for P in water, and P0 = 1 bar. The net reaction (from gas phase P to adsorbed P under aqueous solution) is: 𝑃(𝑔𝑎𝑠) ⇌ 𝑃(𝑎𝑑, 𝑎𝑞), and its equilibrium constant is defined as: 𝑔𝑎𝑠 𝐾𝑒𝑞,𝑎𝑞,𝜃

𝜃 (1 − 𝜃 ) 𝑃𝑃 = / ( 0) 𝜃0 𝑃 ( ) 1 − 𝜃0

Again taking 𝜃 0 as 0.5 and substituting Equation (A8) into Equation (A7) above gives: 𝑃 𝑎𝑞 ( 𝑃0 ) 𝐾𝑒𝑞,𝜃 𝜃 𝑃𝑃 𝑝 𝑔𝑎𝑠 = = ( 0 ) 𝐾𝑒𝑞,𝑎𝑞,𝜃 1−𝜃 𝐾𝐻 𝑃

(A9)

(A10)

As described in the main text, the equilibrium constant is: 𝑔𝑎𝑠 𝐾𝑒𝑞,𝑎𝑞,𝜃

=

𝑎𝑞 𝐾𝑒𝑞,𝜃 /𝐾𝐻

=

0 −∆𝐺𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,𝜃 𝑅𝑇 𝑒

=

0 0 −∆𝐻𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,𝜃 ∆𝑆𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠 𝑅𝑇 𝑅 𝑒 𝑒

(3a)

𝑎𝑞

From our fit to the data, we get 𝐾𝑒𝑞,𝜃 , and values of 𝐾𝐻 for these organics in water are tabulated,36 e.g., 5x10–4 bar/M for phenol at 298 K. Rearranging Equation (3a) gives: 𝑎𝑞 0 0 0 ∆𝐺𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,𝜃 = ∆𝐻𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,𝜃 − 𝑇 ∆𝑆𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠 = −𝑅𝑇 ln(𝐾𝑒𝑞,𝜃 /𝐾𝐻 )

(3b)


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ACS Catalysis

It is convenient to analyze this using the standard-state coverage for which adsorbate entropies have been 𝑎𝑞 tabulated, in which case the value of 𝐾𝑒𝑞,𝜃 determined in Figure 3 needs to multiplied by 𝜃 0 /(1 − 𝜃 0 ), where 𝜃 0 = 0.054 for phenol (see below). For this value and using the equilibrium constant for phenol for 𝑎𝑞 Pt T sites from the fits in Table 1 at this same relative coverage 𝜃 =0.054 of 𝐾𝑒𝑞,𝜃0 = 38, Equation (3b) becomes: 0 0 0 ∆𝐺𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,𝜃,2 = ∆𝐻𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,𝜃,2 − 𝑇 ∆𝑆𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,2 𝑎𝑞

=

𝑔𝑎𝑠 −𝑅𝑇 ln (𝐾𝑒𝑞,𝑎𝑞,𝜃,2 )

𝐾𝑒𝑞,𝜃=0.054 (1 − 𝜃 0 ) − 𝑅𝑇 ln ( ) 𝜃 0 𝐾𝐻

(A11)

where the subscript 2 refers to this new standard-state coverage reference state. 0 To calculate ∆𝐺𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,𝜃,2 using Equation (A11), we will start by assuming that: 0 0 ∆𝑆𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠 ≅ ∆𝑆𝑎𝑑,𝑔𝑎𝑠 𝑛𝑜 𝑠𝑜𝑙𝑣𝑒𝑛𝑡

This assumption of equating the entropy of adsorbed phenol in water (liquid) with the entropy of adsorbed phenol in the absence of liquid (i.e., in gas) is true if the water near the surface has nearly the same entropy independent of whether phenol is there on the surface or not. That is, the interfacial water has similar character whether or not the phenol adlayer is there. It also assumes that we are comparing two states of adsorbed phenol that have essentially the same structure whether or not the water is there above it. This just requires that we must compare to a similar structure in UHV (i.e., in gas) as in aqueous phase. We can use the correlation of Campbell & Sellers40 to estimate entropy of this adsorbed phenol relative to gaseous phenol as: 0 0 0 0 0 0 ∆𝑆𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,2 ≅ ∆𝑆𝑎𝑑,𝑔𝑎𝑠 𝑛𝑜 𝑠𝑜𝑙𝑣𝑒𝑛𝑡,2 = 𝑆𝑎𝑑 − 𝑆𝑔𝑎𝑠 = (0.70𝑆𝑔𝑎𝑠 − 3.3𝑅) − 𝑆𝑔𝑎𝑠 0 = −[0.30𝑆𝑔𝑎𝑠 + 3.3𝑅] 0 The subscript 2 here refers to the different standard-state coverage used there. Using 𝑆𝑔𝑎𝑠 =315 J/(mol K) 0 0 = 37.9 R from reference60 gives ∆𝑆𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,2 ≅ ∆𝑆𝑎𝑑,𝑔𝑎𝑠 𝑛𝑜 𝑠𝑜𝑙𝑣𝑒𝑛𝑡,2 = −14.7 𝑅. However, this value of 0 ∆𝑆𝑎𝑑,𝑔𝑎𝑠 𝑛𝑜 𝑠𝑜𝑙𝑣𝑒𝑛𝑡,2 was determined using a standard-state coverage of

𝜃0 = from ref.

1.17 × 1013 /𝑐𝑚2 𝑆𝑎𝑡𝑢𝑟𝑎𝑡𝑖𝑜𝑛 𝑝ℎ𝑒𝑛𝑜𝑙 𝑐𝑜𝑣𝑒𝑟𝑎𝑔𝑒

16

. Assuming that the saturation phenol coverage = 1/7 of the Pt(111) density,44 this gives 1

𝑆𝑎𝑡𝑢𝑟𝑎𝑡𝑖𝑜𝑛 𝑝ℎ𝑒𝑛𝑜𝑙 𝑐𝑜𝑣𝑒𝑟𝑎𝑔𝑒 = 7 [1.51 × 1015 /𝑐𝑚2 ] = 2.16 × 1014 /𝑐𝑚2, so that 1.17×1013 /𝑐𝑚2

𝜃 0 = 2.16×1014 /𝑐𝑚2 = 0.054. One could correct this entropy to the value of 𝜃 0 used in some places here (𝜃 0 = 1/2) by changing 0 ∆𝑆𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠 by 2.5 R to –17.2 R,16, but we prefer to analyze the data at the lower coverage of 0.054. From our fit of the data from phenol on Pt T sites, we obtain the equilibrium constant in aqueous phase and 𝛼: 𝑎𝑞 𝐾𝑒𝑞,𝜃=0 = 38 (𝑢𝑛𝑖𝑡𝑙𝑒𝑠𝑠), 𝑤𝑖𝑡ℎ 𝛼 = 0 𝑘𝐽/𝑚𝑜𝑙 To calculate the equilibrium constant at a coverage of 𝜃 0 = 0.054, we use (even though it does not affect the result for the T-sites due to 𝛼 = 0 we include it here for completeness):


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𝐽 )(0.054) 𝑚𝑜𝑙 𝐽 𝑒 (8.314𝑚𝑜𝑙𝐾)(298𝐾)

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−(0

𝑒 −𝛼𝜃

0 /𝑅𝑇

=

=1

so that 𝑎𝑞

𝐾𝑒𝑞,𝜃=𝜃0 = 38 Then we can convert the equilibrium constant in the aqueous-phase to a different standard coverage, where instead of 𝜃 0 = 1/2, we use 𝜃 0 = 0.054 where the subscript 2 refers to this new standard-state coverage reference state. 38 𝑔𝑎𝑠 𝐾𝑒𝑞,𝑎𝑞,𝜃=0.054,2 = 0.054 ( ) 5 × 10−4 1 − 0.054 This gives: 𝑔𝑎𝑠

𝐾𝑒𝑞,𝑎𝑞,𝜃=0.054,2 = 1.3 × 106 = 𝑒

0 0 −∆𝐻𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,𝜃=0.054 ∆𝑆𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,2 𝑅𝑇 𝑅 𝑒

This value of the equilibrium constant can be used to calculate the enthalpy of adsorption of gas-phase phenol onto Pt in the aqueous phase using the entropy of this adsorption process estimated above: 0 ∆𝑆𝑎𝑑,𝑔𝑎𝑠,2 𝑔𝑎𝑠 0 ∆𝐻𝑎𝑑,𝑎𝑞,𝑔𝑎𝑠,𝜃=0.054 = −𝑅𝑇 [ln [𝐾𝑒𝑞,𝑎𝑞,𝜃=0.054,2 ] − ] = −𝑅𝑇[ln[1.3 × 106 ] + 14.7] 𝑅 = −𝑅𝑇(28.8) = −71.4

𝑘𝐽 @ 298 𝐾 𝑚𝑜𝑙

ASSOCIATED CONTENT Supporting Information. The following files are available free of charge. CVs at higher concentrations, XANES data before difference and additional EXAFS. AUTHOR INFORMATION Corresponding Author *Email: [email protected], [email protected]. Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT N.S. was funded by the WRF Innovation Fellowship in Clean Energy Institute. The research described in this paper is part of the Chemical Transformation Initiative at Pacific Northwest National Laboratory


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(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. C.T.C. also 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. This research used resources of the Advanced Photon Source Sector 20, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357, and the Canadian Light Source and its funding partners. We thank and acknowledge Mahalingam Balasubramanian for his help. ABBREVIATIONS CV, Cyclic voltammetry; XANES, X-ray absorption near edge spectroscopy; EXAFS, Extended X-ray Absorption Fine Structure; XAS, X-ray Absorption Spectroscopy; Hupd, hydrogen underpotential deposition; RHE, reversible hydrogen electrode; SHE, standard hydrogen electrode; UHV, ultrahigh vacuum. REFERENCES (1) Chheda, J. N.; Huber, G. W.; Dumesic, J. A. Liquid-Phase Catalytic Processing of Biomass-Derived Oxygenated Hydrocarbons to Fuels and Chemicals. Angew. Chemie - Int. Ed. 2007, 46, 7164–7183. (2)

Weber, R. S.; Holladay, J. E.; Jenks, C.; Panisko, E. A.; Snowden-Swan, L. J.; Ramirez-Corredores, M.; Baynes, B.; Angenent, L. T.; Boysen, D. Modularized Production of Fuels and Other ValueAdded Products from Distributed, Wasted, or Stranded Feedstocks. Wiley Interdiscip. Rev. Energy Environ. 2018, 7, e308.

(3)

Zhao, Z.; Bababrik, R.; Xue, W.; Li, Y.; Briggs, N. M.; Nguyen, D.-T.; Nguyen, U.; Crossley, S. P.; Wang, S.; Wang, B.; Resasco, D. E. Solvent-Mediated Charge Separation Drives Alternative Hydrogenation Path of Furanics in Liquid Water. Nat. Catal. 2019, 2, 431–436.

(4)

Song, Y.; Chia, S. H.; Sanyal, U.; Gutiérrez, O. Y.; Lercher, J. A. Integrated Electrocatalytic Conversion of Substituted Phenols and Diaryl Ethers. J. Catal. 2016, 344, 263–272.

(5)

Song, Y.; Sanyal, U.; Pangotra, D.; Camaioni, D. M.; Gutiérrez, O. Y.; Johannes A. Lercher; Holladay, J.; Camaioni, D. M.; Gutiérrez, O. Y.; Lercher, J. A. Hydrogenation of Benzaldehyde via Electrocatalysis and Thermal Catalysis on Carbon-Supported Metals. J. Catal. 2018, 359, 68–75.

(6)

Gomez, R.; Orts, J. M.; Alvarez-Ruiz, B.; Feliu, J. M. Effect of Temperature on Hydrogen Adsorption on Pt(111), Pt(110), and Pt(100) Electrodes in 0.1 M HClO4. J. Phys. Chem. B 2004, 108, 228–238.

(7)

Marković, N. M.; Schmidt, T. J.; Grgur, B. N.; Gasteiger, H. A.; Behm, R. J.; Ross, P. N. Effect of Temperature on Surface Processes at the Pt (111)-Liquid Interface: Hydrogen Adsorption, Oxide Formation, and CO Oxidation. J. Phys. Chem. B 1999, 103, 8568–8577.

(8)

Jerkiewicz, G. Electrochemical Hydrogen Adsorption and Absorption. Part 1: Under-Potential Deposition of Hydrogen. Electrocatalysis 2010, 1, 179–199.

(9)

Wasberg, M.; Hourani, M.; Wieckowski, A. Comparison of Voltammetry of Vacuum-Prepared Rh (100) and Rh (111) Electrodes. J. Electroanal. Chem. 1990, 278, 425–432.

(10)

Sasaki, K.; Kunai, A.; Harada, J.; Nakabori, S. Electrolytic Hydrogenation of Phenols in Aqueous


23

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 28

Acid Solutions. Electrochim. Acta 1983, 28, 671–674. (11)

Deblois, M.; Lessard, J.; Jerkiewicz, G. Influence of Benzene on the HUPD and Anion Adsorption on Pt(1 1 0), Pt(1 0 0) and Pt(1 1 1) Electrodes in Aqueous H2SO4. Electrochim. Acta 2005, 50, 3517–3523.

(12)

Obradović, M. D.; Lessard, J.; Jerkiewicz, G. Cyclic-Voltammetry Behavior of Pt(1 1 1) in Aqueous HClO4 + C6H6: Influence of C6H6 Concentration, Scan Rate and Temperature. J. Electroanal. Chem. 2010, 649, 248–256.

(13)

Gasparotto, L. H. S.; Gomes, J. F.; Tremiliosi-Filho, G. Cyclic-Voltammetry Characteristics of Poly(Vinyl Pyrrolidone) (PVP) on Single-Crystal Pt Surfaces in Aqueous H2SO4. J. Electroanal. Chem. 2011, 663, 48–51.

(14)

Soriaga, M. P.; Hubbard, A. T. Adsorption of Aromatic Compounds at Platinum Electrodes. A Comparative Study Illustrating the Deficiencies of Adsorption Measurements Based on Hydrogen Coedeposition or Anodic Oxidation. J. Electroanal. Chem. 1984, 167, 79–95.

(15)

Schmiemann, U.; Jusys, Z.; Baltruschat, H. The Electrochemical Stability of Model Inhibitors: A DEMS Study on Adsorbed Benzene, Aniline and Pyridine on Mono- and Polycrystalline Pt, Rh and Pd Electrodes. Electrochim. Acta 1994, 39, 561–576.

(16)

Campbell, C. T.; Sprowl, L. H.; Árnadóttir, L. Equilibrium Constants and Rate Constants for Adsorbates: Two Dimensional (2D) Ideal Gas, 2D Ideal Lattice Gas, and Ideal Hindered Translator Models. J. Phys. Chem. C 2016, 120, 10283–10297.

(17)

Jerkiewicz, G.; Deblois, M.; Radovic-Hrapovic, Z.; Tessier, J. P.; Perreault, F.; Lessard, J. Underpotential Deposition of Hydrogen on Benzene-Modified Pt(111) in Aqueous H2SO4. Langmuir 2005, 21, 3511–3520.

(18)

Connolly, J. F.; Flannery, R. J.; Aronowitz, G. Electrochemical Measurement of the Available Surface Area of Carbon-Supported Platinum. J. Electrochem. Soc. 1966, 113, 577–580.

(19)

Stevens, D. A.; Dahn, J. R. Electrochemical Characterization of the Active Surface in CarbonSupported Platinum Electrocatalysts for PEM Fuel Cells. J. Electrochem. Soc. 2003, 150, A770– A775.

(20)

Singh, N.; Nguyen, M.-T.; Cantu, D. C.; Mehdi, B. L.; Browning, N. D.; Fulton, J. L.; Zheng, J.; Balasubramanian, M.; Gutiérrez, O. Y.; Glezakou, V.-A.; Rousseau, R.; Govind, N.; Camaioni, D. M.; Campbell, C. T.; Lercher, J. A. Carbon-Supported Pt during Aqueous Phenol Hydrogenation with and without Applied Electrical Potential: X-Ray Absorption and Theoretical Studies of Structure and Adsorbates. J. Catal. 2018, 368, 8–19.

(21)

Song, Y.; Gutiérrez, O. Y.; Herranz, J.; Lercher, J. A. Aqueous Phase Electrocatalysis and Thermal Catalysis for the Hydrogenation of Phenol at Mild Conditions. Appl. Catal. B Environ. 2016, 182, 236–246.

(22)

Singh, N.; Song, Y.; Gutiérrez, O. Y.; Camaioni, D. M.; Campbell, C. T.; Lercher, J. A. Electrocatalytic Hydrogenation of Phenol over Platinum and Rhodium: Unexpected Temperature Effects Resolved. ACS Catal. 2016, 6, 7466–7470.

(23)

Ravel, B.; Newville, M. ATHENA, ARTEMIS, HEPHAESTUS: Data Analysis for X-Ray Absorption Spectroscopy Using IFEFFIT. J. Synchrotron Radiat. 2005, 12, 537–541.


24

Page 25 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

(24)

Li, C.; Hoffman, M. Z. One-Electron Redox Potentials of Phenols in Aqueous Solution. J. Phys. Chem. B 1999, 103, 6653–6656.

(25)

Gisbert, R.; García, G.; Koper, M. T. M. Adsorption of Phosphate Species on Poly-Oriented Pt and Pt(1 1 1) Electrodes over a Wide Range of PH. Electrochim. Acta 2010, 55, 7961–7968.

(26)

Climent, M. A.; Valls, M. J.; Feliu, J. M.; Aldaz, A.; Clavilier, J. The Behaviour of Platinum SingleCrystal Electrodes in Neutral Phosphate Buffered Solutions. J. Electroanal. Chem. 1992, 326, 113– 127.

(27)

Markovic, N.; Gasteiger, H.; Ross, P. N. Kinetics of Oxygen Reduction on Pt(Hkl) Electrodes: Implications for the Crystallite Size Effect with Supported Pt Electrocatalysts. J. Electrochem. Soc. 1997, 144, 1591–1597.

(28)

Marković, N. M.; Grgur, B. N.; Ross, P. N. Temperature-Dependent Hydrogen Electrochemistry on Platinum Low-Index Single-Crystal Surfaces in Acid Solutions. J. Phys. Chem. B 1997, 101, 5405– 5413.

(29)

Trasatti, S.; Petrii, O. A. Real Surface Area Measurements in Electrochemistry. Pure Appl. Chem. 1991, 63, 711–734.

(30)

Bockris, J. O.; Jeng, K. T. In-Situ Studies of Adsorption of Organic Compounds on Platinum Electrodes. J. Electroanal. Chem. 1992, 330, 541–581.

(31)

Silbaugh, T. L.; Campbell, C. T. Energies of Formation Reactions Measured for Adsorbates on Late Transition Metal Surfaces. J. Phys. Chem. C 2016, 120, 25161–25172.

(32)

Ihm, H.; Ajo, H. M.; Gottfried, J. M.; Bera, P.; Campbell, C. T. Calorimetric Measurement of the Heat of Adsorption of Benzene on Pt (111). J. Phys. Chem. B 2004, 108, 14627–14633.

(33)

Ihm, H.; White, J. M. Stepwise Dissociation of Thermally Activated Phenol on Pt(111). J. Phys. Chem. B 2000, 104, 6202–6211.

(34)

Vassiliev, Y. B.; Bagotzky, V. S.; Khazova, O. A.; Cherny, V. V; Meretsky, A. M. Mechanism of Adsorption, Electroreduction and Hydrogenation of Compounds with Ethylenic Bonds on Platinum and Rhodium Part I. Kinetics of Adsorption and Electroreduction. J. Electroanal. Chem. 1979, 98, 253–272.

(35)

Garrone, E.; Bolis, V.; Fubini, B.; Morterra, C. Thermodynamic and Spectroscopic Characterization of Heterogeneity among Adsorption Sites: CO on Anatase at Ambient Temperature. Langmuir 1989, 5, 892–899.

(36)

Sander, R. Compilation of Henry’s Law Constants (Version 4.0) for Water as Solvent. Atmos. Chem. Phys. 2015, 15, 4399–4981.

(37)

Yang, G.; Akhade, S. A.; Chen, X.; Liu, Y.; Lee, M.-S.; Glezakou, V.-A.; Rousseau, R.; Lercher, J. Nature of Hydrogen Adsorption on Platinum in the Aqueous Phase. Angew. Chemie Int. Ed. 2019, 58, 3527–3532.

(38)

Jiang, Y.; Yang, S.; Li, S.; Liu, W. Aromatic Molecules on Low-Index Coinage Metal Surfaces: Many-Body Dispersion Effects. Sci. Rep. 2016, 6, 39529.

(39)

Sander, R. Henry’s Law Constants. In NIST Chemistry WebBook, NIST Standard Reference Database Number 69, Eds. P.J. Linstrom and W.G. Mallard, National Institute of Standards and


25

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 28

Technology, Gaithersburg MD, 20899; 2018; pp 1–3. (40)

Campbell, C. T.; Sellers, J. R. V. The Entropies of Adsorbed Molecules. J. Am. Chem. Soc. 2012, 134, 18109–18115.

(41)

Costa, F. S.; Eusébio, M. E.; Redinha, J. S.; Leitão, M. L. P. Enthalpies of Solvation of Hydroxyl Cyclohexane Derivatives in Different Solvents. J. Chem. Thermodyn. 1999, 31, 895–903.

(42)

Mintz, C.; Clark, M.; William E. Acree, J.; Abraham, M. H. Enthalpy of Solvation Correlations for Gaseous Solutes Dissolved in Alcohol Solvents Based on the Abraham Model. J. Chem. Inf. Model. 2007, 47, 115–121.

(43)

Abraham, M. H.; Whiting, G. S.; Fuchs, R.; Chambers, E. J. Thermodynamics of Solute Transfer from Water to Hexadecane. J. Chem. Soc. Perkin Trans. 1990, 2, 291–300.

(44)

Carey, S.; Zhao, W.; Mao, Z.; Campbell, C. T. Energetics of Adsorbed Phenol on Ni(111) and Pt(111) by Calorimetry. J. Phys. Chem. C 2019, 123, 7627–7632.

(45)

Lu, F.; Salaita, G. N.; Laguren-Davidson, L.; Stern, D. A.; Wellner, E.; Frank, D. G.; Batina, N.; Zapien, D. C.; Walton, N.; Hubbard, A. T. Characterization of Hydroquinone and Related Compounds Adsorbed at Pt(111) from Aqueous Solutions: Electron Energy-Loss Spectroscopy, Auger Spectroscopy, Low-Energy Electron Diffraction, and Cyclic Voltammetry. Langmuir 1988, 4, 637–646.

(46)

Yoon, Y.; Rousseau, R.; Weber, R. S.; Mei, D.; Lercher, J. A. First-Principles Study of Phenol Hydrogenation on Pt and Ni Catalysts in Aqueous Phase. J. Am. Chem. Soc. 2014, 136, 10287– 10298.

(47)

Honkela, M. L.; Björk, J.; Persson, M. Computational Study of the Adsorption and Dissociation of Phenol on Pt and Rh Surfaces. Phys. Chem. Chem. Phys. 2012, 14, 5849–5854.

(48)

Li, G.; Han, J.; Wang, H.; Zhu, X.; Ge, Q. Role of Dissociation of Phenol in Its Selective Hydrogenation on Pt(111) and Pd(111). ACS Catal. 2015, 5, 2009–2016.

(49)

Réocreux, R.; Huynh, M.; Michel, C.; Sautet, P. Controlling the Adsorption of Aromatic Compounds on Pt(111) with Oxygenate Substituents: From DFT to Simple Molecular Descriptors. J. Phys. Chem. Lett. 2016, 7, 2074–2079.

(50)

Peköz, R.; Donadio, D. Effect of van Der Waals Interactions on the Chemisorption and Physisorption of Phenol and Phenoxy on Metal Surfaces. J. Chem. Phys. 2016, 145, 104701.

(51)

Song, W.; Martsinovich, N.; Heckl, W. M.; Lackinger, M. Born-Haber Cycle for Monolayer SelfAssembly at the Liquid-Solid Interface: Assessing the Enthalpic Driving Force. J. Am. Chem. Soc. 2013, 135, 14854–14862.

(52)

Iyemperumal, S. K.; Deskins, N. A. Evaluating Solvent Effects at the Aqueous/Pt(111) Interface. ChemPhysChem 2017, 18, 2171–2190.

(53)

Yang, J.; Dauenhauer, P. J.; Ramasubramaniam, A. The Role of Water in the Adsorption of Oxygenated Aromatics on Pt and Pd. J. Comput. Chem. 2013, 34, 60–66.

(54)

Rodriguez, J. A.; Campbell, C. T. Probing Ensemble Effects in Surface Reactions. 3. Cyclohexane Adsorption on Clean and Bismuth-Covered Pt(111). J. Phys. Chem. 1989, 93, 826–835.


26

Page 27 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

(55)

Teliska, M.; O’Grady, W. E.; Ramaker, D. E. Determination of H Adsorption Sites on Pt/C Electrodes in HClO4 from Pt L23 X-Ray Absorption Spectroscopy. J. Phys. Chem. B 2004, 108, 2333–2344.

(56)

Reifsnyder, S. N.; Otten, M. M.; Sayers, D. E.; Lamb, H. H. Hydrogen Chemisorption on SilicaSupported Pt Clusters: In Situ X-Ray Absorption Spectroscopy. J. Phys. Chem. B 1997, 101, 4972– 4977.

(57)

Mukerjee, S.; McBreen, J. Hydrogen Electrocatalysis by Carbon Supported Pt and Pt Alloys. J. Electrochem. Soc. 1996, 143, 2285–2294.

(58)

Bus, E.; van Bokhoven, J. A. Hydrogen Chemisorption on Supported Platinum, Gold, and PlatinumGold-Alloy Catalysts. Phys. Chem. Chem. Phys. 2007, 9, 2894–2902.

(59)

Zhao, C.; He, J.; Lemonidou, A. A.; Li, X.; Lercher, J. A. Aqueous-Phase Hydrodeoxygenation of Bio-Derived Phenols to Cycloalkanes. J. Catal. 2011, 280, 8–16.

(60)

Kudchadker, S. A.; Kudchadker, A. P.; Wilhoit, R. C.; Zwolinski, B. J. Ideal Gas Thermodynamic Properties of Phenol and Cresols. J. Phys. Chem. Ref. Data 1978, 7, 417–423.


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Table of Contents Graphic:


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Quantifying Adsorption of Organic Molecules on Platinum in Aqueous

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