Synchrotron based operando surface X‐ray scattering study towards structure–activity relationships of model electrocatalysts

Goryachev, Andrey; Carlà, Francesco; Drnec, Jakub; Onderwaater, Willem G.; Felici, Roberto; Krause, Philipp P. T.; Wonders, AH Ad; Hensen, Emiel Emiel; Hofmann, Jan P.

doi:10.1002/slct.201600355

Cited by 8 publications

(3 citation statements)

References 45 publications

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“…In particular, On‐Line Electrochemical Mass Spectroscopy (OLEMS) was employed to follow gaseous products evolution simultaneously to the applied electrochemical treatment. Combined EC‐OLEMS measurements are commonly used in the field of electrochemistry for an accurate evaluation of electrode performance, stability, selectivity and reaction kinetics . From our studies, we emphasize the importance of using flat thin film model electrocatalyst and compositional analysis of the electrode, electrolyte as well as gaseous products to characterize the intrinsic stability and activity of earth‐abundant electrocatalysts.…”

Section: Introductionmentioning

confidence: 94%

Stability of CoP_x Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water

et al. 2018

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Cobalt phosphides are an emerging earth‐abundant alternative to platinum‐group‐metal‐based electrocatalysts for the hydrogen evolution reaction (HER). Yet, their stability is inferior to platinum and compromises the large‐scale applicability of CoPx in water electrolyzers. In the present study, we employed flat, thin CoPx electrodes prepared through the thermal phosphidation (PH3) of Co3O4 films made by plasma‐enhanced atomic layer deposition to evaluate their stability in acidic water electrolysis by using a multi‐technique approach. The films were found to be composed of two phases: CoP in the bulk and a P‐rich surface CoPx (P/Co>1). Their performance was evaluated in the HER and the exchange current density was determined to be j 0=−8.9 ⋅ 10−5 A/cm2. The apparent activation energy of HER on CoPx (E a=81±15 kJ/mol) was determined for the first time. Dissolution of the material in 0.5 M H2SO4 was observed, regardless of the constantly applied cathodic potential, pointing towards a chemical instead of an electrochemical origin of the observed cathodic instability. The current density and HER faradaic efficiency (FE) were found to be stable during chronoamperometric treatment, as the chemical composition of the HER‐active phase remained unchanged. On the contrary, a dynamic potential change performed in a repeated way facilitated dissolution of the film, yielding its complete degradation within 5 h. There, the FE was also found to be changing. An oxidative route of CoPx dissolution has also been proposed.

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Section: Introductionmentioning

confidence: 94%

Stability of CoP_x Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water

et al. 2018

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“…Spatially resolved data are available from ex situ low-energy electron diffraction (LEED), , in situ X-ray reflectivity, − and in situ electrochemical scanning tunneling microscopy (EC-STM) − experiments. For a brief recent review, see the paper by Drnec et al .…”

Section: Introductionmentioning

confidence: 99%

Atomic-Scale Identification of the Electrochemical Roughening of Platinum

2019

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Electrode degradation under oxidizing conditions is a major drawback for large-scale applications of platinum electrocatalysts. Subjecting Pt(111) to oxidation–reduction cycles is known to lead to the growth of nanoislands. We study this phenomenon using a combination of simultaneous in situ electrochemical scanning tunneling microscopy and cyclic voltammetry. Here, we present a detailed analysis of the formed islands, deriving the (evolution of the) average island growth shape. From the island shapes, we determine the densities of atomic-scale defect sites, e.g., steps and facets, which show an excellent correlation with the different voltammetric hydrogen adsorption peaks. Based on this combination of electrochemical scanning tunneling microscopy (EC-STM) and CV data, we derive a detailed atomistic picture of the nanoisland evolution during potential cycling, delivering new insights into the initial stages of platinum electrode degradation.

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“…Initially both {100} and {111} steps (more precisely, these step sites should be denoted as < 110 > /{100} and < 110 > /{111} respectively, that is, steps along a direction equivalent to [110] and exhibiting a square {100} or hexagonal {111} geometry) form on the roughened surface, while eventually only {111} steps remain. Advanced in situ EC-STM 16,17 and X-ray reflectivity [18][19][20][21][22] experiments are ideal tools to study this system at the atomic level. Using X-ray scattering experiments, and following the surface evolution for 20 ORCs, Ruge et al observed an increasing island size with increasing cycle number and decreasing upper potential limit 21 .…”

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confidence: 99%

Correlation of surface site formation to nanoisland growth in the electrochemical roughening of Pt(111)

et al. 2018

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Platinum plays a central role in a variety of electrochemical devices and its practical use depends on the prevention of electrode degradation. However, understanding the underlying atomic processes under conditions of repeated oxidation and reduction inducing irreversible surface structure changes has proved challenging. Here, we examine the correlation between the evolution of the electrochemical signal of Pt(111) and its surface roughening by simultaneously performing cyclic voltammetry and in situ electrochemical scanning tunnelling microscopy (EC-STM). We identify a 'nucleation and early growth' regime of nanoisland formation, and a 'late growth' regime after island coalescence, which continues up to at least 170 cycles. The correlation analysis shows that each step site that is created in the 'late growth' regime contributes equally strongly to both the electrochemical and the roughness evolution. In contrast, in the 'nucleation and early growth' regime, created step sites contribute to the roughness, but not to the electrochemical signal.

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Synchrotron based operando surface X‐ray scattering study towards structure–activity relationships of model electrocatalysts

Cited by 8 publications

References 45 publications

Stability of CoP_x Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water

Stability of CoP_x Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water

Atomic-Scale Identification of the Electrochemical Roughening of Platinum

Correlation of surface site formation to nanoisland growth in the electrochemical roughening of Pt(111)

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Synchrotron based operando surface X‐ray scattering study towards structure–activity relationships of model electrocatalysts

Cited by 8 publications

References 45 publications

Stability of CoPx Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water

Stability of CoPx Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water

Atomic-Scale Identification of the Electrochemical Roughening of Platinum

Correlation of surface site formation to nanoisland growth in the electrochemical roughening of Pt(111)

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Product

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Stability of CoP_x Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water

Stability of CoP_x Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water