The adsorption of perchlorate, sulfate, selenate and water on Au(111)-textured electrodes from aqueous solutions: Simultaneous voltammetric, optical and microgravimetric studies

Strobl, Jonathan R.; Scherson, Daniel Alberto

doi:10.1016/j.electacta.2021.139107

Cited by 8 publications

(12 citation statements)

References 19 publications

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“…Our results, however, cannot fully explain the drastic difference in EOG activity between neutral and alkaline conditions that is experimentally observed above OH adsorption potentials. As we have shown that adsorbed hydroxides lower the barriers for EOG, to explain this kinetic difference, we suspect the low reaction rates or currents are due to the SO 4 2– and ClO 4 – anions used in neutral EOG experiments. , Both anions are known to specifically adsorb on gold surfaces between 0.2 and 1.05 V RHE and to reach 0.15–0.2 ML surface coverages. , The low currents can be explained by combining the fact that SO 4 2– is adsorbed on the surface at potentials up to 1.2 V RHE at pH = 0, after which Au surface oxidation begins, with the anions’ suspected role in blocking GLY or GLD adsorption . Surface-enhanced IR absorption spectroscopy measurements have also shown that Au(OH) ads and adsorbed SO 4 2– can coexist up to 1.5 V RHE under neutral conditions which coincides well with our calculated OH adsorption potential at pH = 7 and the experimental onset potential around 1.2–1.3 V RHE .…”

Section: Discussionmentioning

confidence: 95%

“…If the error due to the functional is accounted for, then OH adsorption under acidic condition becomes possible at 1.20 V RHE . In addition, experimental measurements are often performed in solutions containing SO 4 2– or ClO 4 – species which also adsorb on gold surfaces and directly influence the OH adsorption/desorption potential under acidic and, to a lesser extent, neutral conditions by blocking possible OH adsorption sites. ,, …”

Section: Resultsmentioning

confidence: 99%

“…For instance, Au’s surface oxidation potential is ∼0.5 V higher than that of Pt indicating that, unlike Pt, Au is not oxidized under the reaction conditions. Au has long been considered totally inactive toward EOG in acidic media due to the lack of proton acceptors such as OH – ions in solution. ,, However, a recent joint experimental and computational study demonstrated that Au retains some activity even under acidic conditions in 0.1 M HClO 4 , while in 0.5 MH 2 SO 4 , no activity was observed. , The differences are likely related to the specific adsorption of (H)SO 4 2– which adsorbs on the surface even in dilute (H)SO 4 2– solutions. , Perchlorate also adsorbs on the Au(111) surface although not as strongly as (hydrogen)sulfate which may explain the differences between the EOG activity in solutions containing ClO 4 – and (H)SO 4 2– . Specifically, sulfates adsorb on the surface around 0.2 V vs RHE (henceforth referred to as V RHE ) in 1.0 MH 2 SO 4 reaching a total coverage of 0.2 monolayer (ML) at 1.05 V RHE while perchlorate adsorbs under more oxidative conditions starting at 0.4 V RHE reaching a 0.15 ML coverage at 1.05 V RHE in 0.1 M HClO 4 …”

Section: Introductionmentioning

confidence: 99%

“…16,19 The differences are likely related to the specific adsorption of (H)SO 4 2− which adsorbs on the surface even in dilute (H)SO 4 2− solutions. 40,41 Perchlorate also adsorbs on the Au(111) surface although not as strongly as (hydrogen)sulfate 42 which may explain the differences between the EOG activity in solutions containing ClO 4…”

Section: ■ Introductionmentioning

confidence: 99%

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Mechanistic Origins of the pH Dependency in Au-Catalyzed Glycerol Electro-oxidation: Insight from First-Principles Calculations

et al. 2021

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Electrocatalytic oxidation of glycerol (EOG) is an attractive approach to convert surplus glycerol to value-added products. Experiments have shown that EOG activity and selectivity depend not only on the electrocatalyst but also on the electrode potential, the pH, and the electrolyte. For broadly employed gold (Au) electrocatalysts, experiments have demonstrated high EOG activity under alkaline conditions with glyceric acid as a primary product, whereas under acidic and neutral conditions Au is almost inactive producing only small amounts of dihydroxyacetone. In the present computational work, we have performed an extensive mechanistic study to understand the pH and potential dependency of Au-catalyzed EOG. Our results show that activity and selectivity are controlled by the presence of surface-bound hydroxyl groups. Under alkaline conditions and close to the experimental onset potential, modest OH coverage is preferred according to our constant potential calculations. This indicates that both Au(OH)ads and Au can be active sites and they cooperatively facilitate the thermodynamically and kinetically feasible formation of glyceric acid thus explaining the experimentally observed high activity and selectivity. Under acidic conditions, hydroxide coverage is negligible and the dihydroxyacetone emerges as the favored product. Calculations predict slow reaction kinetics, however, which explains the low activity and selectivity toward dihydroxyacetone reported in experiments. Overall, our findings highlight that computational studies should explicitly account for pH and coverage effects under alkaline conditions for electrocatalytic oxidation reactions to reliably predict electrocatalytic behavior.

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Section: Discussionmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mechanistic Origins of the pH Dependency in Au-Catalyzed Glycerol Electro-oxidation: Insight from First-Principles Calculations

et al. 2021

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show abstract

Section: ■ Introductionmentioning

confidence: 99%

On the Mechanistic Origins of the pH-Dependency in Au-Catalyzed Glycerol Electro-Oxidation: Insight from First Principles Calculations

Verma¹,

Melander

Honkala³

2021

Preprint

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Electrocatalytic oxidation of glycerol (EOG) is an attractive approach to convert surplus glycerol to value-added products. Experiments have shown that EOG activity and selectivity depend on the electrocatalyst, but also on the electrode potential, the pH, and the electrolyte. For broadly employed gold (Au) electrocatalysts, experiments have demonstrated high EOG activity under alkaline conditions with glyceric acid as a primary product, whereas under acidic and neutral conditions Au is rather inactive producing only small amounts of dihydroxyacetone. In the present computational work, we have performed an extensive mechanistic study to understand the pH- and potential-dependency of Au-catalyzed EOG. Our results show that activity and selectivity are controlled by the presence of surface-bound hydroxyl groups. Under alkaline conditions and close to the experimental onset potential, modest OH coverage is preferred according to our constant potential calculations. This indicates that both Au(OH)ads and Au can be active sites and they cooperatively facilitate the thermodynamically and kinetically feasible formation of glyceric acid thus explaining the experimentally observed high activity and selectivity. Under acidic conditions, hydroxide coverage is negligible and the dihydroxyacetone emerges as the favored product. Calculations predict slow reaction kinetics, however, which explains the low activity and selectivity towards dihydroxyacetone reported in experiments. Overall, our findings highlight that computational studies should explicitly account for pH and coverage effects under alkaline conditions for electrocatalytic oxidation reactions to reliably predict electrocatalytic behaviour.

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Selenate reduction mediated by underpotentially deposited Cu on the low index faces of Au in aqueous perchloric acid

Strobl,

Pathak,

Scherson

2024

Electrochimica Acta

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The adsorption of perchlorate, sulfate, selenate and water on Au(111)-textured electrodes from aqueous solutions: Simultaneous voltammetric, optical and microgravimetric studies

Cited by 8 publications

References 19 publications

Mechanistic Origins of the pH Dependency in Au-Catalyzed Glycerol Electro-oxidation: Insight from First-Principles Calculations

Mechanistic Origins of the pH Dependency in Au-Catalyzed Glycerol Electro-oxidation: Insight from First-Principles Calculations

On the Mechanistic Origins of the pH-Dependency in Au-Catalyzed Glycerol Electro-Oxidation: Insight from First Principles Calculations

Selenate reduction mediated by underpotentially deposited Cu on the low index faces of Au in aqueous perchloric acid

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