The measurements are performed using a micro-electrochemical scanning flow cell (SFC) directly connected to an inductively coupled plasma mass spectrometer (NexION 300×), so that the electrochemical and spectrometric signals are recorded in parallel. The coupled system was described in more detail in our previous studies , . The hardware components are controlled by an in-house programmed LabVIEW application  and the experimental results are presented on synchronized time scales. A
Results and discussion
While our previous conclusions on platinum dissolution were predominantly based on the analysis of the interaction between the Pt surface and the electrolyte, the influence of the reactive gases like hydrogen, oxygen and carbon-monoxide on Pt dissolution was so far not considered. Taking into consideration that the adsorption of these gases can however be competitive with the adsorption of oxygen containing species originating from the solvent itself, and thus potentially interfere with
We present a compact study on Pt dissolution during potential cycling in acidic electrolyte in the presence of various reactive gases. Argon, hydrogen and oxygen do not interfere with the fundamental processes of surface oxidation/reduction and thus the consequent dissolution. However, certain peculiarities are observed in the case of a CO saturated electrolyte, which provides additional important insights into the platinum dissolution mechanism. Adsorbed CO leads to a re-structuring of the Pt
We thank the BMBF (Kz: 033RC1101A) for the financial support.
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Since the 1980s, single-crystal Pt electrodes with well-defined surface structures have been deemed stable under mild electrochemical conditions (e.g., in the potential region of electric double layers, underpotential deposition of hydrogen, or mild hydrogen evolution/OH adsorption) and have served as model electrodes for unraveling the structure-performance relation in electrocatalysis. With the advancement of in situ electrochemical microscopy/spectroscopy techniques, subtle surface restructuring under mild electrochemical conditions has been achieved in the last decade. Surface restructuring can considerably modify electrocatalytic properties by generating/destroying highly active sites, thereby interfering with the deduction of the structure-performance relation. In this review, we summarize recent progress in the restructuring of well-defined Pt(-based) electrode surfaces under mild electrochemical conditions. The importance of the meticulous structural characterization of Pt electrodes before, during, and after electrochemical measurements is demonstrated using CO adsorption/oxidation, hydrogen adsorption/evolution, and oxygen reduction as examples. The implications of present findings for correctly identifying the reaction mechanisms and kinetics of other electrocatalytic systems are also briefly discussed.
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2021, Electrochimica Acta
Isopropanol (IPA) can be used as a rechargeable electrofuel. In this approach, IPA is oxidized to acetone (ACE) in a direct alcohol fuel cell and the formed ACE is subsequently back-converted to IPA in a heterogeneously catalyzed process. To study the electrochemical reaction mechanisms of the IPA oxidation at the molecular level, appropriate and well-defined model electrocatalysts are necessary. In this work we prepare such model electrocatalysts by surface science methods in ultra-high vacuum (UHV). The catalysts consist of well-defined platinum nanoparticles on carbon supports. As carbon support, we use flat highly ordered pyrolytic graphite (HOPG) and thin (20 nm) magnetron sputtered carbon films on a polycrystalline gold substrate. In a first step, we characterize the model electrocatalysts and investigate their stability in-situ with complementary methods, i.e. by electrochemical scanning tunneling microscopy (EC-STM), electrochemical on-line inductively coupled plasma mass spectrometry (ICP-MS) and CO stripping experiments followed by electrochemical infrared reflection absorption spectroscopy (EC-IRRAS). We determined a stability window ranging from -0.65 VRHE to 1.15 VRHE for both sample types, independent of the presence or absence of IPA in the electrolyte. In the second step, we study the oxidation of IPA on tPt nanoparticles using differential electrochemical mass spectrometry (DEMS) and EC-IRRAS. The onset of IPA oxidation is observed at 0.3 VRHE. ACE is formed with high selectivity, while we identify traces of CO2 as the only side-product formed at higher potentials. However, we do not observe any formation of adsorbed CO. A direct comparison of these results with previous work on Pt(111) suggests that low coordinated Pt sites and size effects play a subordinate role for IPA oxidation on Pt electrocatalysts.(Video) Dissolve Platinum with Chlorine Gas
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2021, International Journal of Hydrogen Energy
Proton Exchange Membrane Fuel Cells (PEMFCs) have the perspective to intensely decrease global emission through environmentally-friendly potential. This review paper summarizes the degradation of platinum catalyst layer that has become a significant issue in the improvement of PEMFCs. The review intends to categorise and provide a clear understanding between disintegration and agglomerate that occurs during platinum degradation. In each process, different degradation mechanisms and their migration processes are presented. The improvement in platinum degradation as a function of increasing the performance of PEMFC is established. Prospects for addressing platinum degradation through the exploration of further experimental and numerical research are recommended. Lastly, this paper through recommendation attempts to prevent platinum degradation and reduces high costs associated with the replacement of catalysts in the PEMFCs.
Active electrochemical interfaces stabilized through self-organized potential oscillations
2020, Electrochemistry Communications
Some electrochemical systems are known to have higher average efficiency when operated under an oscillatory regime. Given the compromise between activity and stability, the stability of electrochemical interfaces in a self-organized, oscillatory state must be taken into account. Here we evaluate the electro-oxidation of methanol and formic acid on platinum under regular and oscillatory conditions, and study the stability by following the Pt dissolution rates in situ with a stationary probe rotating disk electrode (SPRDE) coupled to an inductively coupled plasma mass spectrometer (ICP-MS). Generally speaking, as the electro-oxidation reaction proceeds, the platinum dissolution rate increases considerably. To guarantee Pt stability, the potential must be kept below 1.0Vvs.RHE. Interestingly, no dissolution is detectable when the electrode potential undergoes temporary self-organization, ensuring a stable and active interface.
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Pt oxide and oxygen reduction at Pt(111) studied by surface X-ray diffraction
2017, Electrochemistry Communications(Video) How Does Aqua Regia Dissolve Gold and Platinum?
The influence of the oxygen reduction reaction on the oxidation of Pt(111) is studied by surface X-ray diffraction. The oxygen reduction reaction does not significantly influence the place-exchange process during the initial stages of oxidation and there is no change in the onset potential and kinetics.
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