Effect of phosphoric acid purity on the electrochemically active surface area of Pt-based electrodes

Gomes, Bruna Ferreira; Prokop, Martin; Bystroň, Tomáš; Loukrakpam, Rameshwori; Lobo, Carlos Manuel Silva; Kutter, Maximilian; Günther, Timon E.; Fink, Michael; Bouzek, Karel; Roth, Christina

doi:10.1016/j.jelechem.2022.116450

Cited by 6 publications

(7 citation statements)

References 45 publications

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“…46 An increase in CO binding energy (adsorption energy) with decreasing size of Pt clusters was reported 47 and raising surface strain. 48 In any case, present results are in agreement with a previous experimental work 10 showing that the adsorption energies for H 3 PO 4 and CO are lower in magnitude than those obtained for pyramidal H 3 PO 3 , underlining its very specific role. From these data, it was clear that the pyramidal form adsorbs preferentially via the Pt•••P bond and that its adsorption energy is higher than that of the tetrahedral form.…”

Section: Resultssupporting

confidence: 92%

“…Correspondingly, the impact of H 3 PO 3 produced during operation might be one of the reasons for the generally poor performance of HT-PEMFCs in terms of electrode reaction kinetics. Indeed, the negative impact of H 3 PO 3 on O 2 reduction was recently confirmed by Gomes et al using the Pt/C catalyst in a rotating-disc electrode setup. However, the nature of the interaction between Pt and H 3 PO 3 has not been discussed in detail in any of the previously published electrochemical studies.…”

Section: Introductionmentioning

confidence: 66%

“…The Brunauer–Emmett–Teller-determined surface area was found to be 159.8 ± 0.4 m 2 g –1 . Analysis of the transmission electron micrograph shows platinum nanoparticles with a diameter of 2.3 ± 0.7 nm (Figure S1).…”

Section: Methodsmentioning

confidence: 99%

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Following Adsorbed Intermediates on a Platinum Gas Diffusion Electrode in H₃PO₃-Containing Electrolytes Using In Situ X-ray Absorption Spectroscopy

et al. 2022

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One of the challenges of high-temperature polymer electrolyte membrane fuel cells is the poisoning of the Pt catalyst with H3PO4. H3PO4 is imbibed into the routinely used polybenzimidazole-based membranes, which facilitate proton conductivity in the temperature range of 120–200 °C. However, when leached out of the membrane by water produced during operation, H3PO4 adsorbs on the Pt catalyst surface, blocking the active sites and hindering the oxygen reduction reaction (ORR). The reduction of H3PO4 to H3PO3, which occurs at the anode due to a combination of a low potential and the presence of gaseous H2, has been investigated as an additional important contributing factor to the observed poisoning effect. H3PO3 has an affinity toward adsorption on Pt surfaces even greater than that of H2PO4 –. In this work, we investigated the poisoning effect of both H3PO3 and H3PO4 using a half-cell setup with a gas diffusion electrode under ambient conditions. By means of in situ X-ray absorption spectroscopy, it was possible to follow the signature of different species adsorbed on the Pt nanoparticle catalyst (H, O, H2PO4 –, and H3PO3) at different potentials under ORR conditions in various electrolytes (HClO4, H3PO4, and H3PO3). It was found that H3PO3 adsorbs in a pyramidal configuration P(OH)3 through a Pt–P bond. The competition between H3PO4 and H3PO3 adsorption was studied, which should allow for a better understanding of the catalyst poisoning mechanism and thus assist in the development of strategies to mitigate this phenomenon in the future by minimizing H3PO3 generation by, for example, improved catalyst design or adapted operation conditions or changes in the electrolyte composition.

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Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 66%

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Following Adsorbed Intermediates on a Platinum Gas Diffusion Electrode in H₃PO₃-Containing Electrolytes Using In Situ X-ray Absorption Spectroscopy

et al. 2022

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“…In particular, the pyramidal H 3 PO 3 form adsorbs strongly on the Pt surface and the degree of its adsorption increases with rising temperature, which is interesting from the point of view of practical HT-PEMFC applications, operating usually at 120–180 °C. Recently, it was shown that H 3 PO 3 adsorbs strongly also on nanoparticulate Pt, which negatively affects the electrochemically active surface area and kinetics of the O 2 reduction reaction, particularly in the high current density region . Moreover, a recent study showed, through a combination of X-ray absorption spectroscopy at the Pt L 3 -edge and density functional theory, that H 3 PO 3 is more strongly adsorbed on Pt compared to H 3 PO 4 .…”

Section: Introductionmentioning

confidence: 99%

Oxidation of Aqueous Phosphorous Acid Electrolyte in Contact with Pt Studied by X-ray Photoemission Spectroscopy

Wibowo,

Garcia-Diez,

Bystron

et al. 2023

ACS Appl. Mater. Interfaces

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“…On top of these challenges, recent studies also suggest a possible reduction of H 3 PO 4 to H 3 PO 3 during operation conditions of HT-PEMFCs, − which might negatively impact the performance of HT-PEMFCs. − Specifically, the detrimental effect of H 3 PO 3 on the oxygen reduction reaction (ORR) kinetics at the Pt electrode and the stronger adsorption strength of H 3 PO 3 compared to H 3 PO 4 on the Pt catalysts were shown . The strong adsorption of H 3 PO 3 on Pt may cause Pt catalyst poisoning.…”

Section: Introductionmentioning

confidence: 99%

Elucidating the Complex Oxidation Behavior of Aqueous H₃PO₃ on Pt Electrodes via In Situ Tender X-ray Absorption Near-Edge Structure Spectroscopy at the P K-Edge

Wibowo,

Garcia-Diez,

Bystron

et al. 2024

J. Am. Chem. Soc.

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In situ tender X-ray absorption near-edge structure (XANES) spectroscopy at the P K-edge was utilized to investigate the oxidation mechanism of aqueous H 3 PO 3 on Pt electrodes under various conditions relevant to high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) applications. XANES and electrochemical analysis were conducted under different tender X-ray irradiation doses, revealing that intense radiation induces the oxidation of aqueous H 3 PO 3 via H 2 O yielding H 3 PO 4 and H 2 . A broadly applicable experimental procedure was successfully developed to suppress these undesirable radiation-induced effects, enabling a more accurate determination of the aqueous H 3 PO 3 oxidation mechanism. In situ XANES studies of aqueous 5 mol dm −3 H 3 PO 3 on electrodes with varying Pt availability and surface roughness reveal that Pt catalyzes the oxidation of aqueous H 3 PO 3 to H 3 PO 4 . This oxidation is enhanced upon applying a positive potential to the Pt electrode or raising the electrolyte temperature, the latter being corroborated by complementary ionexchange chromatography measurements. Notably, all of these oxidation processes involve reactions with H 2 O, as further supported by XANES measurements of aqueous H 3 PO 3 of different concentrations, showing a more pronounced oxidation in electrolytes with a higher H 2 O content. The significant role of water in the oxidation of H 3 PO 3 to H 3 PO 4 supports the reaction mechanisms proposed for various chemical processes observed in this work and provides valuable insights into potential strategies to mitigate Pt catalyst poisoning by H 3 PO 3 during HT-PEMFC operation.

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Effect of phosphoric acid purity on the electrochemically active surface area of Pt-based electrodes

Cited by 6 publications

References 45 publications

Following Adsorbed Intermediates on a Platinum Gas Diffusion Electrode in H₃PO₃-Containing Electrolytes Using In Situ X-ray Absorption Spectroscopy

Following Adsorbed Intermediates on a Platinum Gas Diffusion Electrode in H₃PO₃-Containing Electrolytes Using In Situ X-ray Absorption Spectroscopy

Oxidation of Aqueous Phosphorous Acid Electrolyte in Contact with Pt Studied by X-ray Photoemission Spectroscopy

Elucidating the Complex Oxidation Behavior of Aqueous H₃PO₃ on Pt Electrodes via In Situ Tender X-ray Absorption Near-Edge Structure Spectroscopy at the P K-Edge

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Effect of phosphoric acid purity on the electrochemically active surface area of Pt-based electrodes

Cited by 6 publications

References 45 publications

Following Adsorbed Intermediates on a Platinum Gas Diffusion Electrode in H3PO3-Containing Electrolytes Using In Situ X-ray Absorption Spectroscopy

Following Adsorbed Intermediates on a Platinum Gas Diffusion Electrode in H3PO3-Containing Electrolytes Using In Situ X-ray Absorption Spectroscopy

Oxidation of Aqueous Phosphorous Acid Electrolyte in Contact with Pt Studied by X-ray Photoemission Spectroscopy

Elucidating the Complex Oxidation Behavior of Aqueous H3PO3 on Pt Electrodes via In Situ Tender X-ray Absorption Near-Edge Structure Spectroscopy at the P K-Edge

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Following Adsorbed Intermediates on a Platinum Gas Diffusion Electrode in H₃PO₃-Containing Electrolytes Using In Situ X-ray Absorption Spectroscopy

Following Adsorbed Intermediates on a Platinum Gas Diffusion Electrode in H₃PO₃-Containing Electrolytes Using In Situ X-ray Absorption Spectroscopy

Elucidating the Complex Oxidation Behavior of Aqueous H₃PO₃ on Pt Electrodes via In Situ Tender X-ray Absorption Near-Edge Structure Spectroscopy at the P K-Edge